HPS111 Introduction to Psychology Notes PDF

HPS111 INTRODUCTION TO PSYCHOLOGY HUMAN BEHAVIOR ================================================ **[WEEK 1 LECTURE NOTES]** **Learning outcomes for this week** [At the end of this topic, you should be able to:] - Define what psychology is. - Briefly describe the history of psychology. -...

HPS111 INTRODUCTION TO PSYCHOLOGY HUMAN BEHAVIOR ================================================ **[WEEK 1 LECTURE NOTES]** **Learning outcomes for this week** [At the end of this topic, you should be able to:] - Define what psychology is. - Briefly describe the history of psychology. - Understand different perspectives in psychology. - Identify several possible career paths in psychology. **[UNIT OVERVIEW]** Structure of weekly activities - Each week you will (approx. 10 hours per week) - Come to/watch the lecture - Come to/work along with the recorded seminar - Associated learning tasks **[ASSESSMENTS]** Three assessments: - AT1 -- week 5 (25%) -- roughly 5-10 hours - AT2 -- week 10 (35%) -- roughly 15-20 hours - AT3 -- end of unit assessment (aka exam; 40%) **[EARLY WORK AND IDEAS -- INTERNAL PROCESSES]** **Early philsophers:** - Aristotle, Socrates through to Descartes, Hobbes, Locke (early empiricist) - Free will vs determinism, mind body problem/ mind body dualism **Early Biological explanations of behaviour (nature):** - Theory of evolution, natural selection (Darwin) - Comparative Psychology - 1879- Wilhelm Wundt starts first experimental lab (Leipzig, Germany) - Structuralism -- Braking down the 'mind' into basic components (earliest studies of cognitive processes) - Functionalism -- examine functions, rather than components (William James) **Psychodynamics -- within the mind:** - Freud and friends (incl. daughter, Anna) - Emphasises unconscious processes and personality - Psychoanalysis -- id, ego, super ego) - Modern -- move from childhood sexual drives to focus on childhood experiences/early relationships (e.g. attachment, Bowlby, Ainsworth) **[20^TH^ CENTURY -- MOVE FROM INTERNAL PROCESSES TO EXTERNALLY OBSERVABLE 'BEHAVIOUR']** **Behaviourism -- examines the role of external factors on behaviours (nurture):** - **PAVLOV** -- classical conditioning - **WATSON** -- focus on 'observable behaviours' - **SKINNER** -- operant conditioning, behaviour modification, Skinner box - Move towards cognitive behaviourism -- thoughts impact behaviour, not just external world. - **BANDURA** -- social cognitive theory. **Humanism** **-- Free will, growth, and meaning** - Hierarchy of needs **(Maslow)** - Person centred approach **(Rodgers)** - Positive psychology! -- study of strengths and what is going 'well' rather than the medical approach to 'fixing' problems **Still interest in the mind:** - Cognitive neuroscience develops (modern biological) **Sociocultural -- moving beyond the self** - Recognises the influences of culture, social norms, group processes (macro) - The influence of individuals like family, workmates, romantic partners (micro) **[The problem of white, cis, hetro, male psychology]** - **Much knowledge about biology, medical and mental health has been generated for the specific group, and generalising to women, non 'Western' and marginalised people doesn't work.** - E.g. ASD/ADHD in girls and women, signs of stroke and heart attack are different for men and women, do you know the difference? Minority stress theories. - E.g. racism in intelligence testing, application of techniques with people from different cultures -- CBT with First Nations people? - Loads of Early conclusions (pre-1995) based on white, largely male student populations (or male rats). Now flipped to female. **SOCIOCULTURAL PERSPECTIVES TRY TO WORK TOWAARDS ADDRESSING THESE ISSUES.** **[BIOPSYCHOSOCIAL MODEL -- WE WILL ADOPT THIS PERSPECTIVE]** - Recognises that cognitions and behaviour might best be explained by the interaction of biology (e.g. genes/ neurotransmitters), Psychology (e.g. neuroticism, optimism/pessimism, rejection sensitivity) and social (e.g., identity, prior experience, social support) factors. - In this unit, we focus on the bio-psycho part of this model, you'll learn more about the psycho-social part in HPS121/HPY713 **[WHAT IS PSYCHOLOGY NOW??]** - In the school we have researchers/educators in the following areas (and more): clinical, mental health, cognitive neuroscience, social, organisational, cognitive, forensic, developmental, personality, relationship, and cross-cultural psychology. - Also, specific areas like aggression, addiction, sleep, memory, autism, adhd, gender and sexuality, suicide, climate change, dark tetrad, connectedness to nature... **Key ideas to take forward:** - **Importance of cross-cultural perspectives** - **Representative groups (not just psych students)** - **Inclusive/collaborative research and codesign** - **New ways of thinking/old ways being considered more.** **[KEY DEFINITIONS/KEY AREAS]** **Psychology: is generally defined as the scientific study of behaviour and mental process. -- Psychology is a science, like most sciences it means that knowledge is built through observation, development of theories/hypotheses, experimentation and interpretation of findings from research to support or refute theories and hypotheses.** **The study of Behaviour: Behaviours are observable actions and responses to the environment, and it includes anything that we can observe in ourselves and others, this includes broad behaviours like interpersonal interactions, learned responses, language, movement, aspects of personality and specific behaviours like smoking/vaping, violence and suicide. Understanding predictors and functions of behaviour can help us to understand why some people might be more or less likely to engage in certain behaviours.** **The Study of Mental Processes: Mental Processes are by their nature not observable, so these can be a little harder to study than behaviours. These internal states, or internal processes include things like cognitions (e.g. thoughts, decision making processes, intelligence) and our feelings (e.g. emotions, motivations and how these might be regulated). Mental processes are involved in behaviour -- e.g. if we take cheating on an assignment or test as an example behaviour, psychology asks 'what made this behaviour happen for this person?** **[WEEK 2 NOTES]** **LEARNING OUTCOMES:** - **Describe the basic structures and functions of the CNS and PNS.** - **Describe the location and function of the lobes of the brain.** - **Describe the basic functions of the ANS.** - **Apply understanding of the ANS to automatic behaviours.** **THE BIOPSYCHOSOCIAL MODEL** - **The first half of the unit is very focussed on the bio only:** - Central and peripheral nervous systems, - Neurons, neurotransmitters, and - How our nervous systems interact with the environment through our senses - **In the second half of the unit, we will bring in psychological part of the model.** - Emotions, learning, memory, communication, intelligence  **[THE NERVOUS SYSTEM]** **[Peripheral Nervous System (PNS) ]** - All the nerves in the body *except* those in the brain and spinal cord - **Two 'branches':** - Somatic Nervous System -- voluntary control of skeletal muscles (e.g. bicep curl) - Autonomic nervous system -- involuntary control/smooth muscles (e.g., heartbeat) **[Autonomic Nervous System ]** ***[Comprises of. ]*** - **Sympathetic** nervous system (activation/arousal e.g. physiological stress response) - **Parasympathetic** nervous system (inhibition/slowing down, return to homeostasis) - Enteric nervous system (controls gastrointestinal tract, brain/gut axis) **[Functions:]** - **Regulates the body** - **'**senses' internally to control glands, smooth muscles (e.g. heart, intestines) and other functions (e.g. respiration, circulation) - Involved in automatic behaviours (e.g. behaviours that we don't have to learn -- are innate), motivation and emotion **EXAMPLE -- Fight/Flight response** - STRESSOR! - Kicks ***[sympathetic nervous system]*** into action, multiple organs impacted to prep the body to fight or flee, blood moves from organs to muscles, HR, PB, body temp all increase (immediate, physiological reaction) - Threat passes ***[parasympathetic nervous]*** helps us return to normal. - We call this **fast fear** response, and it involves the sympathetic adreno-medullary system and hypothalamic-pituitary-adrenocortical (HPA) system The **physiological response** is much the same for everyone**, but:** - For some people, past experiences (e.g. trauma, psychological/social factors) can lead instead to **freeze or fawn** behavioural responses. - In women, this may appear as 'tend and befriend' -- when threatened, woman more likely to tend to children and relationships, and befriend. **Other automatic behaviours: [Reflexes]** - Simple responses to the environment, e.g. 1 stimulus, 1 response - Infants are born with several reflexes focused on survival: - Moro reflex -- startle response - Rooting - Sucking - Grasping (plantar and palmar) - Diving (nirvana album cover) - Tonic neck position (looks a bit like a dab) **Instincts -- examples in animals** - More complex, inbuilt system -- more than just a simple response to the environment, for example - Salmon returning to where they were spawned, to spawn - Turtle hatchlings head to the sea after hatching - Whales/ birds migrating **[UNIT SITE NOTES]** **2.1 EVOLUTION OF THE BRAIN** - The human brain is a specially evolved organ that allows us to solve problems unique to humans and has allowed us to flourish as a species. - What are the evolutionary advantages and disadvantages of humans having such a large and metabolically expensive brain, relative to all other species on our planet? - Although it only makes up about **2-3% of your total body weight**, the brain can use anywhere between **20 -- 30% of your daily energy allowance.** - That means that almost **a third of our daily caloric intake** from the food we eat is used to keep the **brain running.** **WHY IS IT THAT WE HAVE SUCH DEMANING BRAINS?** there are several distinct advantages to humans having such a large brain, including our abilities to: - Make and use tools - Solve old as new problems we have never encountered before - Use language and symbols to communicate efficiently and effectively - Engage in abstract thought by using logic - Remember past experiences and to apply things we have learned to current and future problems - Live in highly complex social groups with large number of other humans **BRAIN SIZE AND INTELLIGENCE** - Compared to other species, humans are capable of several unique and highly adaptive cognitive abilities which are made possible by our large and metabolically hungry brains. - *Does this mean humans have the biggest brains?* - Human brains in absolute terms Rae larger than many other species (e.g. dogs, cats ect) - HOWEVER, when compared to some of the larger species of animals such as whales and elephants, human beings have smaller brains. ***[IT IS IMPORTANT TO NOTE THAT HUMANS DO NOT POSSESS THE LARGEST BARIN OF THE SPECIES ON EARTH BECAUSE THIS DEMONSTARTES HAVING A LARGER BRAIN DOES NOT EQUATE TO A SPECIES BEING MORE INTELLIGENT. IF IT DID, WE'D EXPECT LARGER MAMMALS TO BE MORE INTELLIGENT THAN HUMANS. ]*** **ENCEPHALISATION QUOTIENT (EQ)** - A more reliable metric of the relationship between a species' intelligence and their brain size is to measure brain mass while controlling for the size of the animal's body. - Scientists have performed these calculations to determine what is referred to as the '***encephalisation quotient' (EQ)*** - A species EQ is calculated by taking the log of a species average brain mass and dividing it by the log of the species average body mass. **[LOG OF A SPECIES AVERAGE BRAIN MASS / LOG OF THE SPECIES AVERAGE BODY MASS]** - The metric provides us a way of quantifying a species brain size relative to its body mass and allows for us to make accurate comparisons of the brain sizes across species. - Overall, EQ provides a useful way for understanding the relationship between a species' brain size (as a ratio of body size) and its intelligence. - When using this metric, we tend to find that animals capable of more intelligent behaviours have higher EQ's. Mammals (including humans) tend to have the highest EQ's, followed by birds, reptiles, amphibians, and then by bony fish. **ONE LIMITATION OF EQ** - One example of where EQ fails to accurately determine the relative to their body size, chihuahuas have a higher EQ's than human beings, while being less intelligent as a species. **THE CEREBRAL CORTEX** - One characteristic that differentiates the human brain from other animals is having a highly developed cerebral cortex compared to other species.  - The cerebral cortex is the outer-most layer of our brain. - This region contains many higher-order abilities as thought to be uniquely human, including complex thinking and language learning. - The human brain also has many structures below the cortex, which we refer to as the sub-cortical structures, which are involved with motivation and emotion. - These are believed to be very "primitive" processes which are needed across all species for basic survival, so it stands to reason these would be in the primitive structures of the brain that are more like those seen in other animals. ***LEARNING CHECK -- FOCUS QUESTIONS*** 1. What is the relationship between brain mass and intelligence? For humans, because of our large and metabolically hungry brains we have many unique and highly adaptive cognitive abilities. In comparison to many other animals the size of our brain in absolute terms is larger therefor our big brain mass equates to being more 'intelligence'. However, this is not the case regarding larger animals like whales and elephants, we are found to have smaller brains. Having a larger brain does not equate to a species being more intelligent. 2. What is the encephalisation quotient? Why is this useful? a species EQ is calculated by taking the log (a specific mathematical equation) of a species average brain mass and dividing it by the log of the species average body mass. -- this provides us a way of quantifying a species brain size compared to its body mass. EQ is useful for us to understanding the relationship between a species brain size and its intelligence. When EQ is used, its finds that animals who have capabilities of higher intelligence have a higher EQ. 3. Where is the cerebral cortex? How is this different in humans compared to other animals? The cerebral cortex is the outer layer of our brain and is responsible for our higher-order abilities that are unique to humans, those abilities include higher-complex thinking and language learning. The cerebral cortex is thought to be the differentiating factor between humans and other animals. **[2.2 THE CEREBRAL CORTEX (CORPUS CALLOSUM AND OVERVIEW OF THE FOUR LOBES)]** *The cerebral cortex is **the outermost layer of the brain** and is about **2 centimetres thick.*** - The word ***cortex*** is Latin for "bark" -- the outer covering the brain resembles tree bark, covered in wrinkles, folds and depressions. - ***The Bulgy parts of the cortex are called the "gyri***" - ***The depressions or valleys are called the "sulci"*** - ***The very deep valleys are referred to as "fissures"*** ***There may be adaptive advantages to the cerebral cortex having this wrinkly shape.*** - one theory is that the folded shape increases the available surface area of the brain. - The shape of the cerebral cortex may mean we can fit a larger amount of brain mass into the very small space that is available within our skulls, - creating more availability for more functions within the brain - the cerebral cortex is theorised to be the most recently evolved region of the brain. - Containing many of the **'higher order'** functions that humans are believed to evolve the most recently, e.g. our advanced language, planning, and thinking abilities. **[CORPUS CALLOSUM]** *[There are 2 sides of the brain -- the left and right hemisphere -- all connected by a bridge of neural tissue known as the **"corpus callosum"**]* - The **corpus callosum allows information from one hemisphere to be shared with the corresponding contralateral, or opposite, side of the brain.** - The is important because each hemisphere receives information from the opposite side of the body - For example, motor information from the right side of the body is received and controlled by the left hemisphere and vice versa. - The brain functions most effectively when the left and right hemispheres can communicate vis the corpus callosum. - HOWEVER, there is a form of psychosurgery called ***split brain surgery*** where the corpus callosum is surgically cut so that left and right hemispheres become unable to communicate. **[SPLIT BRAIN SURGERY]** - Split brain surgery can be used as a treatment for severe forms of epilepsy. E.g.: - When seizures begin in one-hemisphere of the brain and migrate to the other hemisphere via the corpus callosum, resulting in a "grand ma seizure" affecting both sides of the body. - In these cases, splitting the corpus callosum can isolate the seizure to only one side of the brain. - Surprisingly people recover quite well following the surgery but can display unusual behavioural effects if tested on specific tasks. **[THE LOBES OF THE CEREBRAL CORTEX]** The outer layer of the cerebral cortex can be divided into four lobes: 1. The **frontal lobe.** 2. The **parietal lobe.** 3. The **temporal lobe.** 4. The **occipital lobe.** **[LEARNING CHECK]** 1. **What are sulci and gyri? Why do we think we have them?** **Sulci:** the bulgy parts of the cerebral cortex **Gyri:** the depression and valleys It's hypothesised that we possess a folded and bulgy shape of the cortex so we can fit more available surface area of the brain. It allows us to fit more brain into a small amount of space. 2. **The brain is split into hemispheres (halves) connected by what structure? Why might you sever this? What happens when you do?** the corpus collosum is the structure that connects the two regions and is responsible for communication between the two regions. Some who have severe epilepsy will have a surgery to cut the corpus collosum, aiming for seizures to remain in one region and prevent grand ma seizures where both sides of the body are affected. People spuriously recover well but can show unusual behavioural effects on specific tasks. It can create a response where if an image is flashed to the right hemisphere, people will see nothing but when asked to pick up the object, they will do so with their left hand (their right hemisphere controls this). Meaning although they cannot see the object their brain subconsciously is aware. 3. **What are the 4 lobes of the cortex? Try to draw a brain and label them.** - Frontal lobe - Parietal lobe - Occipital lobe - Temporal lobe. **[2.3 THE CEREBRAL CORTEX (FRONTAL LOBES)]**  1. **[THE FRONTAL LOBES]** - The frontal lobes are found **towards the front of the head, and before the midline.** - The frontal lobes consist of several regions which are involved with ***self-initiated voluntary movement***, ***aspects of personality***, ***working memory***, ***reward and punishment,*** and ***decision making.*** **DORSOLOATERAL PREFRONTAL CORTEX (DLPFC)** - The frontal lobes contain a region known as the **DLPFC.** - It is found at the **midpoint of the frontal lobes, in front of the motor cortex**. The DLPFC are involved with a collection of cognitive processes we call our ***executive functions,*** an umbrella term for: - Problem solving - Holding things in working memory - Engaging in deep thought - Maintaining our goals or rules when preforming tasks - Manipulating information for problem solving - Future planning and inhibition **PRIMARY MOTOR CORTEX (M1)**  - Just behind the DLPFC is the **primary motor cortex,** which is the region of the frontal lobe that is involved with the *initiation of voluntary movement.* - The M1 is the **strip of brain that runs from the top of your skull down to where your ears are.** - **The top regions of M1** control your **feet, legs, groin and torso** - **The lower parts of M1** control your hands**, arms, face and tongue muscles.** - There are **bigger regions** of this space **devoted to the movement of the hands and face areas**, and comparatively **less space devoted to the movement of the legs and torso --** humans have significantly more abilities for fine motor movements using our hands and feet, compared to our legs and torso. **BROCA'S AREA** - Area involved with **language processing** and specifically **influences our ability to produce speech.** - **Named after a surgeon names Pierre Paul Broca** -- he discovered that damage to this part of the brain meant patients with a very specific type of language impairment couldn't produce fluent speech. - **"Tan" most famous patient** -- lost his ability to speak at 30 and could follow instructions and commands and communicated by gesturing but his speech was limited to a single monosyllabic word 'tan'. - **After his death,** Broca found widespread atrophy to the brain and there was one region above the left temporal lobe of tan's brain that showed a high amount of damage **[Broca's Aphasia (non-fluent aphasia) --]** impairment of the ability to produce fluent speech, EVEN if isn't caused by specific damage to Broca's area. Speech may be purposeful and meaningful but very laboured, slow and filled with pauses and "ums" **[LEARNING CHECK]** 1. **Where is the primary motor cortex? (Can you draw and label it?)** **Within the frontal lobe (near the front of the brain) and is a strip that runs from the top of your skull down to your ears.** 2. **Which body parts have larger representations in the motor cortex? Why?** **Your hands and face muscles because as humans we use far more minor motor muscles in our hands and facial muscles compared to the rest of our body.** 3. **The DLPFC is involved in what types of cognitive functions?** - **Executive functions.** - **Concentration** - **Mood** - **Planning and time management** - **Complex thought** - **Working memories** - **Goals and rules when doing a task** **[2.4: THE CEREBRAL CORTEX (PARIETAL LOBES)]** **[2. THE PARIETAL LOBES]**  - Located **just behind the frontal lobes are the parietal lobes** - ***Known for their involvement with the processing of sensory information, but also help us with our spatial navigation and spatial awareness*** **PRIMARY SOMATOSENSORY CORTEX (S1)** - The parietal lobes contain a **strip of brain matter, located next to the primary motor cortex**, known as the **primary somatosensory cortex.** - The S1 is the region of the brain which processes incoming sensory information **relating to feelings of touch.** - Any type of sense perception including pressure, pain, and temperature is sent from either the CNS (through the cranial nerves), or the PNS (through the spine) to the somatosensory cortex for further processing. **SIMILARITIES BETWEEN THE SOMATOSENSORY CORTEX AND MOTOR CORTEX** - Just like the primary motor cortex, the somatosensory cortex is organised in hierarchical manner, **where the legs, torso and feet are represented higher up** on the somatosensory cortex, **with the hands, face and neck areas being represented further down.** - Also like the primary motor cortex, there is a **greater proportion** of the somatosensory **cortex dedicated to regions such as hands and face, as opposed to our body and legs** -- **this is due to our hands and face being more sensitive to touch than other parts of our body** **MORE ABOUT THE RELATIONSHIP BETWEEN THE PRIMARY SOMATOSENSORY CORTEX AND THE PRIMARY MOTOR CORTEX** - Anatomically, the primary somatosensory cortex and the primary motor cortex are side by side. **SPATIAL AWARENESS, SPATIAL NAVIGATION AND HEMISPATIAL NEGLECT** - Another **function** of the parietal lobe, including the **somatosensory cortex**, is **spatial awareness** and **spatial navigation** around our environments. - **The parietal lobe** is involved with ensuring that we can update our current positions in space, **allowing us to interact with objects in our environments** - **The somatosensory cortex** helps with **spatial navigation** because we need to be able to perceive our bodies so we can move our body through our environment. **E.g. if our brains did not know where our eyes are, it would not be possible to direct our attention to objects around us.** **HEMISPATIAL NEGLECT** - Hemispatial neglect is **condition where individuals tend to ignore the left side of space or objects** (relative to their perspective) - Essentially as though **the left side of space no longer exists for them.** - The partial neglect of space can be caused by **damage to the right partial cortex. (Although damage to frontal or subcortical regions can also induce the disorder.** - One of the ways which clinicians test for Hemispatial neglect is to have a patient with the condition copy images of symmetrical objects. **LEARNING CHECK** 1. **Where is the Somatosensory cortex? (Can you draw and label it?)** The somatosensory cortex is in the parietal lobes next to the primary motor cortex and looks like a long strip of matter. 2. **What does the somatosensory cortex do? How do we know?** the S1 is responsible for any sensory information being perceived by the brain in relation to touch. Any kind of pain, pressure and temperature is either sent from the CNS or the PNS is send to the S1 for further processing. 3. **How is the Somatosensory cortex comparable to the Motor cortex?** Both cortex's have an organisational placement, with legs, feet and torso represented higher up and hands and face lower down. And the amount of allocated space for hands and feet is much larger in both brain regions in comparison to legs, feet and torso. They are also physically next to each other. 4. **What else does the parietal lobe do? How do we know?** The partial lobe is also responsible for spatial awareness and navigation and allows us to create a map of our surroundings and ensure we don't bump into things. A way for us to know is when there is damage to this region due to a condition called hemispatial neglect where individuals tend to ignore the left side of objects or space. Clinicians can test this by asking those individuals to replicate drawings of symmetrical images, its demonstrated that those individuals fail to produce detail of the left side of the drawing. **[2.5 THE CEREBRAL CORTEX (OCCIPITAL LOBES AND TEMPORAL LOBES)]**  **THE OCCIPITAL LOBES** - the occipital lobes are **found near the base of the spine, just above the hindbrain** - These lobes house the regions of the brain involved with visual processing. -- we know because these lobes connect to the optical nerve from the eyes and neuroimaging research and brain damage in these regions. - **Cortical blindness** -- visually unable to see or severely impaired and will struggle on visual tasks (unable to name objects presented to them) **RARE VISUAL CONDITIONS FROM DAMAGE TO OCCIPITAL LOBES** **[Achromatopsia:]** only a few cases have been recorded, this condition involves the inability to see in colour. Patients report seeing their world in shades of grey, monotone or less bright and may have difficulty name colours. **[Akinetopsia:]** involves having difficulties perceiving movement, reported to be caused by damage to the occipitotemporal cortex. **THE TEMPORAL LOBES** - The temporal lobes are **located below the frontal lobes, and just before the occipital cortex.** - Associated with several important **functions including auditory processing, object recognition and facial perception, and memory processes** **AUDITORY PROCESSING** - The temporal lobes contain the **primary auditory cortex** which is involved with processing of sound information. - Evidence for this comes from anatomical studies showing that if we trace the auditory nerve from the ears, it makes its way via the thalamus, to the auditory region in the temporal lobes. - Neuroimaging studies have shown that **the auditory cortex becomes active** when people **listen to different types of sounds** including speech and non-speech sounds. - **Sound information is sent from the ears, via the auditory nerve,** **then the primary auditory cortex for processing** so you can understand the words that are being said. - Your brain **decodes the information it receives from the ears to** **detect where sounds are coming** from around you in 3-dimensional space, allowing us **to identify the location of objects** in the environment, which helps detect danger near us. **FUSIFORM FACE AREA (FFA)** - The right temporal lobe contains a region that appears to be specialised for the recognition of human faces, referred to as the ***fusiform face area.*** - we associate this region with facial recognition because damage to the right temporal lobes can result in a condition known as **prosopagnosia,** ***where patients lose the ability to recognise previously familiar faces.*** - **Visual agnosia:** another disorder which can be caused by damage to the temporal lobes which affects our ability to recognise visual objects. **WERNICKE'S AREA** - A region of the temporal lobe that's involved with language processing and specifically influences our ability to **comprehend speech**. - **WERNICKE'S APHASIA:** a language disorder where patients can produce speech that is very fluent; however, the speech itself can be nonsensical and convey very little substantive meaning. - They may use very circumstantial speech or use filler words, when they cannot find the word, they are looking for. - Extreme difficulty comprehending language in either written or verbal form. **LEARNING CHECK** 1. **Where does auditory information get processed in the brain?** **In the primary auditory cortex, which is in the temporal lobes. Behind the temples on your skull.** 2. **What's the name of the brain region involved in face detection? Where is it? (Can you draw and label it?)** **The Fusiform Face Area (FFA) which is a region in the RIGHT temporal lobe.** 3. **Damage to the temporal lobes can cause different conditions, name and describe them ** **Prosopagnosia:** when people lose the ability to recognise faces, they have seen before which is caused by damage to the FFA. **Visual agnosia:** another condition cause by damage in the FFA is characterised by the inability to recognise visual objects. **Wernicke's aphasia:** a condition from damage in the Wernicke's area, that involves patients producing fluent speech but struggle with using filler words or circumstantial speech when they can't find a word they're looking. Also have trouble comprehending written or verbal language. 4. **What are the two areas associated with language that were described? What are they each involved in?** **Primary auditory cortex:** this region is responsible for processing sound information, including speech and non-speech sounds language. It travels from the nerves in our ears, then via the thalamus ten to the auditory region in the brain. **Wernicke area:** this area is responsible for language processing and our ability to comprehend speech. 5. **Describe and compare the two types of aphasias discussed.** **[Broca's Aphasia (non-fluent aphasia) --]** impairment of the ability to produce fluent speech, EVEN if isn't caused by specific damage to Broca's area. Speech may be purposeful and meaningful but very laboured, slow and filled with pauses and "ums" **Fluent aphasia/Wernicke's aphasia:** can produce speech that is very fluent, but the speech itself can be nonsensical and convey very little meaning. May use very circumstantial speech or filler words when they cannot find the word they're looking for. **[2.6 THE NERVOUS SYSTEMS]** - We have two interconnected systems on display here: - The **central nervous system (CNS);** the brain and the spinal cord - The **peripheral neverous system (PNS);** a complex system of nerves that exists **BRANCHES OF THE PNS** 1. **Somatic nervous system** a. Involved in skeletal muscles, under **voluntary control**, motor and sensory nerves b. Walking exercising, and intentional movements are all 'controlled' by the somatic nervous system. 2. **Autonomic nervous system (ANS)** c. Parallel to the spinal cord. Involved with smooth muscles (e.g. heart, blood vessels, intestine, glands) under **involuntary control.** d. Digestion, breathing heartrate, are all regulated by the ANS. The ANS is also responsible for homeostasis e. The ANS is further broken down into 2 main branches: **sympathetic and parasympathetic nervous system.** **Branches of the Autonomic nervous system (ANS)** 1. **Sympathetic nervous system** a. the alert system b. this is what is activated when we need to react to something e.g. stress response fight/flight 2. **Parasympathetic nervous system** c. The 'rest and 'digest' system d. Inhibits activation, or helps the body return to baseline/homeostasis A screenshot of a medical report Description automatically generated **[2.7 AUTOMATIC BEHAVIOURS -- REFLEX AND INTINTICS]** - Automatic behaviours are things we do **without conscious control.** - they can keep us safe or reduce our cognitive overload. - These are inbuilt automatic behaviours we all have (e.g. reflexes) - OR they may be things that we repeat so often that they become automatic **REFLEXES** - Reflexes are **simple responses to the environment** - *One stimulus = one response* Common reflexes include. - The knee tap reflex - Reflex action that occurs when we touch something hot - Pupillary dilation/constriction - Swallowing - Breathing **INFANT REFLEXES** Infants are born with several reflexes, focused on survival, that disappear over time: - Moro reflex (startle response) - Rooting reflex (to find the nipple) - The sucking reflex (to aid feeding) - Grasping reflex (palmer -- hand, plantar -- foot) - Driving reflex (hold breath under water, breathe when air flows over face) - Tonic neck position **INSTINCTS** - Instincts are easiest to understand in animals though humans have instincts too -- self-preservation is one, as in the urge to tend to cry human babies. - Instincts are complex responses than reflexes, they are **more than a single stimulus and response** but are **still built in** and **not learned.** [Some examples of instincts in animals are:] 1. Salmon spawning -- return to the same breeding grounds ever year, not taught 2. Turtle hatchlings heading to the sea after hatching 3. Whales migrating 4. Birds performing elaborates dances for their prospective mates **[NOTE: THERE IS NO CEREBRAL CORTX INVOLVEMNET IN REFLEXES. THERE ARE CONTROLLED BY THE PNS.]** **[WEEK 3: CENTRAL NERVOUS SYSTEM (CNS)]** **[INTRODUCTION TO THE HINDBRAIN, MIDBRAIN AND FOREBRAIN]** Many ways to group and organise the different structures of the brain but a commonly used system divides the brain into three sections: 1. **The hindbrain** 2. **The midbrain** 3. **The forebrain** 1. **THE HINDBRAIN** The hindbrain sits at the base of the skull and is comprised of several brain regions including: I. The **medulla oblongata** II. The **pons** III. The **reticular formation** IV. The **cerebellum** I. **THE MEDULLA OBLONGATA** - The medulla oblongata is **found just on the top of the spine and is considered an extension of the spinal cord** (think of it as the area where the spine and brain connect.) - This region is very important for **several critical life functions** including **cardiovascular control such as breathing and heart rate**, and many life-critical reflexes such as vomiting, coughing, and sneezing. - The medulla has several sensory and motor pathways making connections with different muscles and sensory receptors in the face, mouth, neck and shoulders. - Due to the importance of this region in vital life function, receiving damage to the medulla oblongata can be life threatening. II. **THE PONS** - The next region that is part of the hindbrain is **the pons.** The pons **sits on the top of the medulla oblongata**. It contains several pathways that send information from the face, eyes and ears to the brain. - The words "pons" is Latin for "bridge", and it is this because it is the location where neurons from one side of the brain crossover and connect with the opposite or "contralateral" side of the body. - The pons is also involved with regulation of sleep, particularly a type of sleep known for rapid eye movement (REM) sleep. - REM sleep the period of sleep where most dreaming occurs: - the pons is responsible for keeping your body immobile while in dreaming sleep, so you do not move around and potentially harm yourself acting outing your dreams. III. **THE RETICULAR FORMATION** - The reticular formation is found deep within the medulla and the pons - The role is the regulation of attention, arousal, wakefulness and sleep. - Damage to this area of the brain can result in falling into a comatose state or even death. - We know this because there were several studies conducted in the early 1930s and 1940 showed the lesioning regions within the reticular formation of cats would either lead to a comatose state or even death. - Other studies have shown that is possible to induce sleep in cats by stimulating certain parts of the reticular formation, or alternatively stimulating other regions to get a sleeping cat to wake up. - The reticular formation contains a pathway known as the "ascending pathway" - This ascending pathway sends information from the lower sections of the nervous system -- that is, from your body -- to higher cortical regions of the brain to be further processed and understood. - As such, one role of the reticular formation is to serve as an entrance gate where information from the body can reach the brain. IV. **THE CEREBELLUM** - The cerebellum is a large structure that has many deep folds, making it look like a miniature version of the cerebral cortex. It is located at the bottom of the brain. - The word cerebellum means "little brain". The cerebellum is a part of the hindbrain that works unconsciously to coordinate aspects of motor control, including our balance, gait and posture. - Specially, the cerebellum helps to smooth out motor movements so that we can move effortlessly in our environments. - There is a condition called cerebellar hypoplasia where the brain region is underdeveloped, and this can result in movements which appear uncoordinated, deliberate, and unstable. **LEARNING CHECK** I. **What are the parts of the Hindbrain?** the medulla oblongata, the pons, the reticular formation, the cerebellum II. **What part of the brain is responsible for breathing and heart rate?** the medulla oblongata III. **There are two parts of your brain described as being involved in sleep, what parts are they, and what specifically do they do?** The Pons -- involved with regulation of sleep and specifically REM sleep, the pons is responsible for keeping your body immobile while dreaming so you don't harm yourself in your dreams and The reticular formation -- which has the role in the regulation of attention, arousal, wakefulness and sleep, damage to this area of the brain can result in falling into a comatose state or even death. IV. **Information from your body (muscles, organs, and glands) comes through which hindbrain region?** The medulla oblongata V. **The cerebellum is located where in your brain?** Located at the bottom of the brain VI. **What is the cerebellum important for?** The cerebellum works unconsciously to coordinate aspects of motor control, including our balance, gait and posture. Specifically, the cerebellum helps to smooth out motor movements so that we can move effortlessly in our environments. **3.2: BRAIN ANATOMY: SUB-CORTICAL STRUCTURES (MIDBRAIN)** - The next region of the brain -- the midbrain -- sits on top of the hindbrain. - The midbrain comprises several structures that are involved with a range of different processes. - For example, the midbrain is made up of: i. The **superior colliculus**, which is involved with aspects of vision and eye movements ii. The **inferior colliculus**, which is involved with aspects of hearing iii. The **tectum** iv. the **tegmentum** v. the **substantia nigra --** involved with things including movement, reward, and motor control - although the functions of the midbrain are important, they are not the functions we often associate with so called "higher order" abilities such as language, emotions, cognition, or our personality -- the structures within the midbrain are not associated with us being "human" - many of the functions which are more developed or even unique to humans are contained within the forebrain. - Thus, another function of the mid-brain is to connect between the evolutionary "older" hindbrain and the evolutionarily "newer" forebrain, to allow communication these brain regions. 3. **[BRAIN ANATOMY: SUB-CORTICAL STRUCTURES (FOREBRAIN)]** **THE FOREBRAIN** - The **forebrain** is considered a part of the brain which humans have evolved more recently. - **It is located around and above the midbrain** and thought to be the location of many of our more "human" functions - The five prominent and important forebrain structures: - The thalamus - The hypothalamus - The basal ganglia - The hippocampus - The amygdala \^ together these constitute the limbic system which has roles in emotion and memory I. **THALAMUS** - The thalamus is found in the center of the brain and can be used as reference point to navigate around the brain. - The thalamus comprises two structures, one contained in the left and one in the right hemispheres. - The thalamus acts as a relay station that sends sensory information -- including our sense of touch, taste, vision and hearing -- on to the primary cerebral cortices for further processing **THE THALAMUS AND OUR SENSES** Researchers have found that there are certain regions within the thalamus which connect to other brain areas. E.g.: - Information about taste gathered from our tongue is sent to the thalamus and then onto the "gustatory cortex" - Visual information from our eyes is sent to the "lateral geniculate nucleus" of the thalamus then to the "primary visual cortex" for visual processing. - Sound information from the ears is sent to the "*medial geniculate nucleus*" of the thalamus then onto the "*auditory cortex*" for further processing. - Finally, information from our senses in relation to touch, pain, pressure, and temperature are sent from our sensory neurons to the thalamus, and then onto the "*primary somatosensory cortex*" in the parietal lobes. **THE THALAMUS AND SPATIAL LEARNING AND NON-SPATIAL MEMORY** - The thalamus is involved in functions other than sending sensory information to the cortex, it is also involved in spatial learning and non-spatial memory. - Spatial learning is about learning the location of objects in the environment and their relative relationship to one another - Think of it as the learning which happens when you move to a new area and need to re-learn the locations of where all the different buildings are in relationship to your house. II. **THE HYPOTHALAMUS** - the next region we will discuss is the "hypothalamus". The word "hypo- "means "below" or "under", so the hypothalamus describes the brain structure located just below the thalamus. - Although the hypothalamus is very small brain region, it is involved with many important motivational approach and avoidance type behaviours. - Specifically, the hypothalamus has been associated with what we call "four F's" -- **fighting, fleeing, feeding and fornicating** **THE HYPOTHALAMUS AND LESION STUDIES** - Evidence that the hypothalamus is involves with these four functions comes from various lesion studies which have shown that if different regions of the thalamus are destroyed via ablation, it will affect motivation to perform these behaviours. - Case study by Anand and Brobeck -- the researchers damaged part of the hypothalamus known as the ventromedial hypothalamus, so towards the bottom of the center of the hypothalamus, which resulted in increased eating behaviour, leading to obesity in the rats. - The researchers also found that lesions to the lateral hypothalamus, which is just a side of the hypothalamus, resulted in decreased eating behaviour which led to starvation and eventually death of the rats - Other studies using cats and rats to study aggressive behaviours have shown that electrical stimulation of certain parts of the hypothalamus can result in defensive behaviours in these animals, such as arching of the back, retraction of the ears, aggressive vocalizations, and other behaviours - You can also induce a peripheral nervous system response where you see increases in heart rate, blood pressure, and the release of adrenaline by electrically stimulating the hypothalamus. III. **BASAL GANGLIA** - Another important subcortical region which is involved with several aspects of **movement, emotional regulation and cognition** is known as the **"basal ganglia"** - The basal ganglia **comprise several components** or **"nuclei",** including **the globus pallidus, caudate nucleus, putamen, the subthalamic nucleus** and **the substantia nigra.** - The basal ganglia **are found deep with the brain, just beside the thalamus and extending into the lower hindbrain.** - The basal ganglia are involved with many aspects of **motor control, memory, and emotional expression.** - The basal ganglia are involved with the **initiation of planned and coordinated motor movements -- e.g. when playing a musical instrument:** - *Initially playing a new musical instrument ius very difficult as you are not yet familiar with how to play the notes* - *However, the more experience, you start to become much more proficient and fluid in your ability to play the instrument* - **the basal ganglia** are one part of the brain which is active to help you learn the coordinated movements require to play an instrument. **THE GANGLIA AND PARKINSONS DISEASE** - the basal ganglia are **also involved with the initiation of spontaneous movement.** - **Damage to the basal ganglia** have been implicated in movements disorders such as **Parkinson's disease.** - **Parkinson's disease:** people often show several symptoms including tremor rigidity, difficulties in initiating, and difficulties stopping movements, in addition to non-motor issues such as depression anxiety and cognitive impairment. - **Development in treatment:** - **Deep brain stimulation can be used to help treat some of the motor symptoms present in Parkinson's disease** - E.g. surgeons might target connections between different structures within the basal ganglia or globus pallidus to alleviate some of the symptoms. **THE BASAL GANGLIA, THE NUCLEOUS ACCUMBENS AND REWARD SEEKING** - Another function that the basal ganglia, and more specifically the **nucleus accumbens**, are involved in is reward seeking. - "reward" refers to any behaviour the organism finds pleasurable, including eating, drinking, playing video games, gambling, sexual behaviours, but also use of recreational drugs and alcohol. - **One of the most famous studies -- showed that the nucleus accumbens is involved with reward conducted by the Olds and Milner (1954)** - **In this study, they surgically implanted electrodes into a region of the brain called the septum in a group of rats** - **They found that when they stimulated that region, the rats acted as though they had experienced something pleasant by sniffing the air around them** IV. **THE HIPPOCAMPUS** - A subcortical region which is crucial to our memory is the **"hippocampus".** - Hippocampus is Greek for the word 'seahorse; because, if you look at a picture of the hippocampus, it does look somewhat like a seahorse, - We have **two hippocampi**, **one in each hemisphere**, and they are **located to the side of the thalamus and basal ganglia,** - ***The hippocampi have an important role encoding new memories and in consolidating short-term memory into long term memory stores.*** - *Every time you form a new memory about your life -- be it information about what you ate for breakfast, what you did yesterday, what you did last week, or what you did on your 18^th^ birthday -- you will need to activate the hippocampus.* - **the hippocampus is also involved in learning new facts and knowledge about the world.** - *It will because active when you are in a formal learning environment, such as when you are trying to learn the information in one of your subjects for a test.* - **The hippocampus also consolidates information you have learned into long-term memory stores, allowing you store and then retrieve that information later when it is needed.** - **You also need your hippocampus for spatial learning and memory**. - *Whenever you need to generate a map in your mind to go to a location you have seen before, the hippocampus becomes active.* **[THE CASE OF "H.M"]** - **HM was a man in the 1950's who suffered from severe epilepsy** -- evidence at the time was the hippocampus was involved with the generation of epileptic seizures, and it was decided they would remove both of HM's hippocampi to attempt to stop his seizures. - **while the surgery was successful in controlling the seizures, it resulted in very serve and unintended memory deficits for HM.** - HM suffered with ***anterograde amnesia, a memory condition where he was unable to form any new memories of events which had occurred after the surgery had taken place*** - ***HM could still remember how to perform certain physical or motor behaviours, e.g. he was able to learn how to draw the outline of a star using only the reflection in a mirror increasingly well over time. -- HM retained the ability to form memories if the information does not activate the hippocampus when being learned.*** V. **AMYGDALA** - The final subcortical region we will discuss is the **"amygdala".** - Amygdala is the Greek word for "almond" -- **it is a small, almond shaped brain structure that is located near the end of the hippocampus.** - Just like the hippocampus, **you have two amygdales, one in hemisphere of your brain.** - The amygdala has traditionally been **associated with fear and aggression response in organisms** -- if you stimulate certain areas within the amygdala via brain stimulation, this can cause animals to elicit express aggressive behaviours. - In addition to its **role in emotion --** there is increasing evidence to show the amygdalae are involved with a much wider range of processes -- **e.g. as a "relevance detector" for stimuli in the environment.** - the amygdala may be a system which is **constantly scanning for information which may or may not be relevant to you**. - Many **fMRI studies** showing that the amygdala **is involved in several important functions, including processing of negative and positive emotions, processing social information, and supporting memory and learning.** **LEARNING CHECK** 1. **What does the thalamus do?** The thalamus acts as a relay station that sends sensory information- including our sense of taste, touch, vision and hearing- on to the primary cerebral cortices for further processing e.g. information about taste gathered from our tongue is sent to the thalamus and then onto the gustatory cortex. 2. **What evidence is there for the importance of the thalamus to memory?** in one study, researchers taught rats to learn a sequence of smells placed in different locations around a small room in a particular order. They then gave the rats a task where they were encouraged to follow the same sequence of smells that they learnt previously. The researchers found damaging certain parts of the thalamus impaired the rat's ability to perform the tasks 3. **What activities are the hypothalamus involved in? How do we know that?** the hypothalamus is involved in motivational and avoidance type behaviours and is associated with the four F's flight, flee, feeding and fornicating. In rats damage to this region increased in increased eating leading to obesity and damage to the lateral hypothalamus resulted in decreased eating behaviour leading to starvation and eventually death. Other studies indicated that electrical stimulation to this brain region demonstrated defensive behaviours in cats and rats, arching of the back, aggressive vocalisations etc. 4. **What happens when the basal ganglia are damaged, and what does this tell us about what the basal ganglia does?** **The basal ganglia are implicated in motor control, memory and emotional expression, damage to this region can seem in those with Parkinson's disease where they have trouble initiating and stopping motor movements, tremors and difficult emotions such as depression and anxiety. And stimulation of parts of these regions has shown to have improvements of these symptoms.** 5. **What condition can be treated by targeting regions associated with the basal ganglia?** **Parkinson's disease** 6. **The Hippocampus is involved in what important processes?** the hippocampus is involved in the role of encoding and consolidating short term memory into long term memory and involved in learning new facts and knowledge about the world. 7. **The Amygdalae are traditionally associated with what? What evidence is there for this?** the amygdalae have been traditionally associated with fear and aggression responses in organisms, if you stimulate certain areas within the amygdalae vis brain stimulation, this can cause animals to elicit aggressive behaviours. 8. **What is a more modern representation of the role of the Amygdalae?** Increasing evidence is showing the amygdalae is involved with our "relevance" detector and scans the environment to seek stimuli that may or may not be relevant to you and has several important functions like processing of negative and positive emotions, processing social information and supporting memory and learning. 4. **[METHODS FOR STUDYING THE BRAIN (BRAIN DAMAGE AND PSYCHOSURGERY)]** 1. ***[BRAIN DAMAGE]*** - One way to understand the association between brain and behaviour is to investigate what happens when the is damaged either intentionally or accidently. - Accidental damage can include any type of physiological trauma such as damaged caused by disease processes (such as viruses or bacteria) or an unfortunate accident (soldiers who sustain brain damage, road trauma, concussion or work-related accidents) **PHINEAS GAGE** - Phineas cage was a rail worker and in 1848 he was the victim of an unfortunate accident involving explosives and an iron tampering rod. - The tamping **iron pierced the lower half of his eye socket and exited through the top of his skull, damaging the front of his brain (which we now call the orbitofrontal cortex)** - Amazingly, he survived, **BUT people reported that Gage's behaviour and personality changed substantially after the accident, including reports that he went from a very diligent sociable and dependable worker to being rude, impatient and disorganized.** - One of the limitations of brain damage to learn the functions of different regions of the brain is that these accidental brain injuries often occur under very controlled circumstances - this makes it very difficult to draw strong conclusions regarding the damage and any resulting damage in behaviour, especially if the damage is very widespread, or occurs to multiple regions of the brain. **CHRONIC TRAUMATIC ENCEPHALOPATHY** - A more recent example of brain damage studies is seen with (CTE). - Only diagnosable after death and has been frequently seen in sports people and more recently in the brains of 2 indigenous Australian women. **Learning Check** 1. What is the relationship between brain mass and intelligence? 2. What is the Encephalisation quotient? Why is this useful? 3. Where is the Cerebral cortex? How is this different in humans compared to other animals? 2. ***[PSYCHOSURGERY]*** - Another research paradigm that is often used in this area to use animal models to better understand hoe specific brain regions may be involved in the generation of specific behaviour. - Frequently, this type of research involves ablation (which is the surgical removal of brain tissue), or by inserting electrodes into specific areas of the brain, to examine how this disrupts behaviour. - This type of research has often used animals that are biologically like humans, such as acts, rodents or primates - It is noted that there are very strict rules governing the use of animal research in Australia must be adhered to on all animal research studies. **HEMISPHERECTOMY** - Another technique which can be used to gain insight into the brain is psychosurgery - In some severe mental illnesses or treatment-resistant conditions -- a medical team may legion regions of the brain which are known to be involved with the expression of disorders. - A surgery called 'hemispherectomy' can be performed in which an entire hemisphere of the brain that is causing the seizures is removed. **DEEP BRAIN STIMULATION (DBS)** - A technique that is more reversable (but no more technical) involves the insertion of electrodes into the brain, known as ***deep brain stimulation (DBS).*** - Electrodes are inserted into the brain so that those regions can be electrically stimulated for therapeutic benefit. - **DBS is used in treatment of multiple conditions**, **such as treatment resistant major depression disorder and motor tremor associated with Parkinson disease.** - Electrodes are implanted into brain structures insides the brain associated with the condition so that these structures can be electrically stimulated and activated. - Since 1964, there has been a strict set of ethical principles regarding human research experimentation, called the ***declaration of Helsinki,*** which all research studies involving human participants must adhere to. **[3.5: METHODS FOR STUDYING THE BRAIN (NEUROIMAGING AND BRAIN STIMULATION)]** 3. **NEUROIMAGING** - With advances in technology, we can now use neuroimaging techniques to study the human brain. -- neuroimaging techniques basically attempt to measure neural activity in the brain. - **These techniques can be categorized as either:** - **'Non-invasive' techniques:** non-invasive techniques are used to study the brain *without the need for surgery of* other invasive procedures. - **'invasive' techniques:** invasive techniques *may require surgery* **COMMON NEUROIMAGING TECHNIQUES** - **Electroencephalography (EEG)** - **Functional magnetic resonance imagery (fMRI)** - **Positron emission tomography (PET)** **[EEG]** - This technique involves the use of **recording electrodes that are placed at various locations on the scalp to record the electrical activity being produced in the underlying regions of the brain.** - The technique does not produce any electrical stimulation which enters the brain, EEG only records the electrical currents produced by the brain and presents them as an **'EEG trace'** - ***EEG is used to measure brain responses very, very quickly and get a clearer picture of how things occur in the brain over time. --*** EEG is very good at recording when something happens in the brain. - An EEG trace is somewhat like **replaying brain activity in slow motion**. - E.g. we might want to see how quickly the brain responds when it is surprised: - We record EEG across the scalp while showing someone a series of pictures of different people who are all smiling. - After showing several minutes of showing only faces of people smiling, we may then show the participant a picture of an individual who is frowning and use EEG to measure their brain's reaction to the image. - The EEG trace would be able to show how quickly the individuals brain responses to the surprising image with **incredible accuracy, down to 1/1000^th^ of a second.** **STRENGTHS AND WEAKNESSES OF EEG** **Strength:** has very high temporal precision. High temporal precision essentially means EEG is very accurate in recording when something occurs in the brain. **Weakness:** it has poor spatial resolution; it can be very difficult for us to know where in the brain the electrical signals we are recording originate from when using EEG. **[MRI]** - Uses powerful magnetic fields to detect and measure different types of tissue in the brain and body -- **MRI created a static magnetic field and uses pulses to measure how the hydrogen atoms respond to the magnetic field** - the scanner can be set up so you can detect things such as white matter, grey matter, cerebrospinal fluid and the skull. - **MRI offers a high level of spatial resolution and can identify different regions of the brain with millimeter precision.** **[fMRI]** - A variant of MRI called **FUNCTIONAL magnetic resonance imaging (MRI).** - **fMRI measures neural activity indirectly by measuring oxygenated blood versus deoxygenated blood levels with specific regions of the brain.** - *The assumption is that more oxygenated blood means that there's more neural activity occurring in a region of the brain requiring that region to temporarily consume more oxygen* - This change is where oxygenated blood present in the brain is called the 'blood-oxygen-level-dependent' (BOLD) contrast and is what is being measured by fMRI. - **This technique can be used to measure which different brain regions become active when people perform or undergo different types of tasks.** **STRENGTHS:** it is incredibly accurate at showing where things occur in the brain with millimeter precision. **WEAKNESS:** because it is measuring changes in blood flow, and it can take blood several seconds to reach those regions it is need it, it is incredibly imprecise at measuring when a change occurs within the brain **[PET]** - One invasive neuroimaging technique is known as **positron emission tomography (PET).** - **This technique involves the use of radioactive chemicals which are injected intravenously** (via a canula inserted into a vein). - The radioactive materials called radiotracers bind to different molecules in the brain, such as glucose or water. - These scans are then able to provide similar types of information to an fMRI scan but showing how brain processes unfold over time. **STRENGTHS AND WEAKENNESS OF PET:** offers relatively good spatial resolution, the technique is like fMRI in having somewhat poor temporal resolution. A table of text with black text Description automatically generated with medium confidence 4. **[BRAIN STIMULATION]** **TRANSCRANIAL MAGNATIC STIMULATION (TMS)** - Brain stimulation technologies can again be divided into non-invasive and invasive techniques. - One prominent non-invasive technique is called TMS: - Uses electromagnetic fields to induce an electrical current outside the brain. - Can be used for cortical mapping studies, where we can stimulate regions of the brain that represent different body parts and see how the body reacts to the stimulation. - It is also possible to use TMS to examine the parts of the brain which are associated with psychological process, such as language, executive functioning or thinking. - TMS can be administered above a region of the brain thought to be involved in a cognitive ability to temporarily "turn on" or "turn off" that brain region. **DEEP BRAIN STIMULATION (DBS)** - **Deep brain stimulation (DBS) is an invasive form of brain stimulation** - DBS involves the insertion of electrodes into the brain via psychosurgery - DBS has been used to treat disorders such as Parkinson's disease, essential tremor, major depression and OCD **[3.6: LIMITATIONS OF NEUROBIOLOGICAL APPROACHES]** **LIMITATION 1: CONFLATING "DESCRIPTION" WITH "EXPLANATION"** - The first issue is the danger of conflating "description" with "explanation", we have described different functions that appear to be associated with a given region of the brain -- but **we have not been able to do is explain how this works.** - **E.g.:** you may know that the amygdala is involved with fear processing, but we cannot say with confidence exactly how the amygdala does this. **LIMITATION 2: IMPACT OF PHRENOLOGY ON OUR CURRENT APPAROACH** - According to phrenology, certain characteristics could be predicted by the shape and size of different regions of an individual's skull. Are modern brain imaging techniques all that different from phrenology? - With modern techniques like fMRI and PET, although we can show that a specific brain region may be "active" when a person performs the task, we still do not know how that brain region performs that task **LIMITATION 3: BRAIN AREAS DO NOT ACT IN ISOLATION** - Finally, it is crucial to note that no area of the brain acts in isolation, every single brain region is heavily connected with many others. Due to this, the view that a single region contributed to a single function is overly simplistic and does not accurately reflect how the brain works **[WEEK 4 NOTES]** Learning objectives: 1. Understand the basic biological structure and function of neurons. 2. Understand the processes of 'Step A' of intra-neuronal communication, involving transmission of electrical information from axon hillock to the terminal buttons. 3. Understand the processes of 'Step B' of intra-neuronal communication, involving transmission of electrical information from dendrites to the axon hillock. 4. Understand the processes of 'Step C' of inter-neuronal communication, involving transmission of chemical between neurons. 5. Recognise six major neurotransmitter types and be able to describe the role/s of each in cognition, affect, and behaviours. **[4.1 BASIC STRUCTURE AND FUNCTION OF A NEURON (PART 1)]** - Neurons are the **individual nerve cells** which **make up the brain and nervous system** - **Neurons communicate using a combination of electrical and chemical processes** - Neurons are the **most fundamental** unit in our nervous system - Your nervous system is through to comprise between **10 and 100 billion neurons** - More importantly, neurons are **highly integrated,** with each neuron estimated to be in communication with a thousand other neurons **[CLASSIFYING NEURONS BY FUNCTION]** At a broad functional level, neurons can be classified as three types: 1. ***Sensory neurons*** - Sensory neurons are those which transmit information from sensory receptors in the body to the brain for further processing. 2. ***Motor neurons*** - Motor neurons do the opposite; they are involved with transmitting information from the brain to the muscles and organs in the body, with instructions for them on how to function. **Sensory and motor neurons can be very long,** sometimes spanning the entire length of your body. **For example**, a sensory receptor in your big toe is attached to a single sensory neuron which travels the entire length of your body from the toe, through the spinal cord, to your brain. 3. ***Interneurons*** - The third functional types of neurons, called **interneurons,** are those which simply transmit information from one neuron to another neuron. - Interneurons make up most of the neurons in your brain. **[THE STRUCTURE OF A TYPICAL NEURON]** **SOMA, CELL BODY, AND DENDRITES** **The 'Soma' or 'cell body'** - where all the important processing of the neuron occurs. - When you think about your brain 'working', this work is being done in the cell body. **Nucleus** - Inside the cell body is the nucleus, which contains a copy of all your DNA - Because of this, you can think of the nucleus, and specifically the DNA it contains, as the control house for all the instructions for how the neuron is structured and needs to function. **Dendrites** - Feeding into the cell body are the "dendrites". - These dendrites receive information from the other neurons **AXON HILLOCK, AXON, MYELIN AND NODES OF RANVIER** **Axon and Axon Hillock and Terminal Buttons** - Extending from the cell body is the **axon** with the area connecting to the cell body to the axon called the **axon hillock** - The axon is responsible for transmitting electrical signals from the cell body through the **"terminal buttons",** which is where information is conveyed to other neurons **Myelin** - Most of the axon is covered with what is known as **"myelin".** Myelin is a white fatty substance produced by subtypes of glial cells. - An important function of this myelin is to insulate the electrical signal that is transmitted through the axon (and it is myelin that is impacted in multiple sclerosis) **Nodes of Ranvier** - The entire axon is not covered in myelin, instead it is interspersed with sections that are unmyelinated. These are called **"nodes of Ranvier"** - Together with the axon hillock, the nodes of Ranvier are the sections of the axon where an important process called the "action potential" occurs. - The action potential is the process that propagates an electrical signal from the axon hillock to the end of the neuron to allow information to be transmitted to the dendrites of the next cell. **The Synapse** - Neurons **do not** interact with one another through direct contact - There is a tiny gap between the terminal buttons at the end of one neuron and the dendrites of the next neuron. - The gap is called the "**synapse"** or the "**synaptic cleft"**, this is where chemicals are released from the terminal buttons on one neuron (i.e., a **pre-synaptic neuron**) to communicate a new signal to the dendrites of the next neuron (i.e. a **post-synaptic neuron)** 2. **[BASIC STRUCTURE AND FUNCTION OF A NEURON]** **CLASSIFYING NEURONS BY STRUCTURE** *Another way we can classify neurons is based on structure.*  **[NEURON 1: Unipolar Neuron]** - Neuron 1 is called a unipolar neuron. - It has one projection from the cell body, which can sometimes be a dendrite or an axon depending on its function. **[NEURON 2: Bipolar Neuron]** - Neuron 2 has two projections and is known as a bipolar neuron. - These types of neurons are most known for their important role in the visual system. **[NEURON 3: Multipolar neuron]** - Neuron 3 is the prototypical neuron that we examined previously. - These are known as multipolar neurons and are the most common type of neuron in the brain. **[NEURON 4: Pseud-Unipolar Neuron]** - Neuron 4 presents what are known as pseudo-unipolar neurons. - It is pseudo-unipolar because, although it only has one projection from the cell body, it still is comprised of both dendrite and an axon. - These pseudo-unipolar neurons are most observed as the long sensory and motor neurons which traverse the entire length of your body **[WHITE AND GREY MATTER]** **[Grey Matter]** - grey matter comprises of **cell bodies and dendrites of neurons** - the cell body of the neuron is where all the information processing occurs - much of the grey matter are located on the **outside** of the brain, in the area known as the cerebral cortex - the cortex is involved in the processing of information, so its logical that these cortical brain regions contain enormous amounts of cell bodies of neurons to serve as the areas where the brain processes information. - It should be noted that there are some deep lying grey matter regions, so it is not a rule that grey matter is only seen in the cortex **[White matter]** - White matter are the **myelinated axons of neurons** - Much of the **inside** of the brain is white matter, comprising enormous networks of myelinated axons. - The white matter areas are mainly about the transmission of the information from different grey matter areas. - The corpus callosum -- which is the brain structure with the function of allowing communication between the hemispheres of the brain -- is entirely white. This is because it is entirely comprised of the axons of different neurons which are spanning from one side of the brain to the other. - The same is true for the spinal cord, which is entirely white because it comprises just the huge, long myelinated axons projecting to and from our body and the brain. **[NEURONAL COMMUNICATION: STEP A, STEP B AND STEP C]** **Step A** - Within (intra-) neuron communication - Process by which dendrites and cell bodies receive inputs from nearby neurons - A process of electrical communication - This is an all-or-nothing signal called an **action potential** **Step B** - Within (intra-) neuron communication - Process by which information travels from the axon hillock, along the axon, to terminal buttons - A form of electrical communication **Step C** - Between (inter-) neuron communication - Process by which a signal reaching the terminal button causes the releases a chemical signal across the synapse, communicating with nearby neurons - A form of chemical communication 3. **['STEP A OF NEURAL COMMUNICATION]** **TRANSMISSION OF THE ELCETRICAL INFORMATION FROM DENDRITES TO THE AXON HILLOCK** **Intra-neuronal communication** - Involves the communication of electrical information - Steps A and B describe how the communication of electrical information within neurons occurs. **[FOUNDATIONAL TERMINOLOGY]** **Ion -- cation and anion** - **An ion is molecule or chemical that has a charge** - That charge can be positive or negative - A positively charged ion is called a **"cation".** A negatively charged ion is called an **"anion"** - These ions are found naturally both inside and outside of a cell. **Diffusion and Electrostatic Pressure** - **Diffusion** *is the passive movement of the substance from an area of high concentration to low concentration* - **i.e.,** when you place a drop of food dye into water -- initially the dye is in high concentration where you drop it, but over time, the dye spreads out and moves to those areas where it is of low concentration -- unit it is spread evenly throughout the water. - **Electrostatic pressure** *is the passive attraction of oppositely charge ions, and repulsion of similarly charged ions, and repulsion of similarly charged ions.* - **Ions behave similarly way magnets do** - This is the same as the way ions interact, which is what electrostatic pressure describes. - Negatively charges ions want to go to areas where it is more positively charged and avoid where it is negative. Positively charged ions want to go where it is negative and avoid where it is positive. - Diffusion and electrostatic pressure are that they can make ions move around depending on: - 1\. Their concentration (i.e. by diffusion they want to go where they have low concentration) - 2\. Whether the area they are located has net negative or positive charge. - These processes are passive, meaning they just occur naturally, but when taken together they create a dynamic situation where the concentrations of ions can change rapidly given appropriate conditions inside and outside of the neuron.  **INSIDE AND OUTSIDE A BRAIN CELL (NEURON)** - The inside of the neuron is known as the **"intracellular space"** - The outside of the neuron is known as the **"extracellular space"** - Separating the intra- and extra-cellular space is the wall of the cell, known as the **"cell membrane"** - An important feature of the cell membrane is that it is **semi-permeable**, meaning that some things can pass through the membrane, whilst others cannot - This **"semi-permeability"** of the cell membrane is made possible by the opening and closing of different **ion channels** located in the membrane which can allow certain ions to pass through easily, while preventing the passage of other ions. - These ion channels can be opened or closed by electrical stimulation; it is possible to control the movement of ions across the cell membrane depending on specific signals which are received by a neuron. **IONS INSIDE AND OUTSIDE A CELL** - At rest, when the neuron is not being stimulates, the **intracellular space has an overall negative charge** and the **extracellular space has an overall positive charge** -- this is mostly due to some very large molecules inside the cell that cannot leave, and which happen to have a negative charge. - The cell wants to maintain this highly negative charge inside the cell at rest and will actively "kick out" some positively charged molecules to achieve this. - This overall negative charge inside the neuron relative to the outside of the neuron is called the **"membrane potential"** - There is an overall negative charge inside of a neuron when it is at rest, and this resting membrane potential is a direct function of the relative concentration of different types of negatively and positively charged ions spread across the different sides of the cell membrane. - The membrane potential when a neuronal cell is at rest, known as the **"resting membrane potential"**, has a value of approximately -70 millivolts (mV) **MOVING IONS WILL CHANGE THE MEMBRANE POTENTIAL** *if we were able to open certain ion channels in the membrane that allow for certain positively charged ions to move to wherever they wanted to be?* **they will want to go inside the cell:** 1. The ions that are positively charged, and the inside of a cell is negatively charged at rest, due to electrostatic pressure the positive ions will be attracted towards the negative ions and want to enter the cell 2. If the positive ions are in high concentration outside the cell, they would again want to enter the cell due to processes of diffusion  **DEPOLARISATION AND HYPERPOLARAISATION** - At rest, the resting membrane potential is -70mV. By manipulating the cell membrane in some way, it is possible for the relative concentrations of different types of positively and negatively charged ions to move in and outside the cell. - **If the effect of a manipulation causes the inside of the cell to become less negative, it is said to have caused the membrane potential to "depolarize"** - **A manipulation causing the membrane potential to depolarize is considered an "excitatory signal" or excitatory potential"** - **By contrast, the effect of a manipulation causes the inside of the cell to become more negative, it is said to have caused the membrane potential to "hyperpolarize".** - **A manipulation causing the membrane potential to hyperpolarize is called an "inhibitory signal" or "inhibitory potential"** **THE GRADED POTENTIAL** - Excitatory and inhibitory signals received by a neuron (via the dendrite and cell body) are called **"graded potentials"** - They are called this because the ability of an electrical signal being received by a neuron to tell it what to do is directly related to how strong that signal is. - The signals are **graded** based on how strong they are. - If there is a stronger excitatory signal being received, more "excitation potential" signal will enter the neuron, resulting in the neuron becoming more depolarized. - In contrast, there is stronger inhibitory signal being perceived, more "inhibitory potential" signal will enter the neuron, resulting in the neuron becoming hyperpolarized. - However, it is important to note that you can get graded potentials cancelling each other out - If you have an excitatory signal being conducted through the dendrites and it meets an inhibitory signal, it will cancel out. **GRADED POTENTIALS CONVERGE AT THE AXON HILLOCK** - All those graded potentials that are passively conducted through the dendrites and cell body converge at the axon hillock - Therefore, it is the axon hillock that is determined whether the electrical signal will continue one, or not. - All the graded potentials -- excitatory and inhibitory -- coming from all the other neurons surrounding a neuron are all fighting to have the overall net effect. - ***You get the excitatory graded potentials saying: "go neuron go! Continue transmitting the message to the next neuron!*** - ***By contrast, you have the inhibitory graded potentials saying "stop the signal! Stop the signal! No more communication to the next neuron. Stop the information flow!*** - It is only when these signals converge at the axon hillock, and net effect of all those graded potentials is calculated, that is determined whether the neuron is going to continue transmitting the signal to the next neuron or not. - When a neuron does continue transmitting the signal to the next neuron, it is commonly referred to ad getting the neuron to 'fire' - Whether a neuron will fire or not depends on t hent effect of all the excitatory and inhibitory graded potentials that converge at the axon hillock. **[4.4: 'STEP B' OF NEURONAL COMMUNICATION:]** **TRANSMISION OF ELECTRICAL INFORMATION FROM AXON HILLOCK TO THE TERMINAL BUTTONS** **STEP B -- THE ACTION POTENTIAL** - Step B of neuronal communication, which is about how information is transferred through the axon - Communication through the axon occurs via an electrical signal called an **"action potential".** - **The action potential is the big event, the 'firing' or the 'not firing' of a neuron** - Unlike step A which involves a graded response based on the number of excitatory and inhibitory inputs via the dendrites, an action potential is an **"all-or-nothing" process.** - It either happens or it doesn't happen - It is the action potential that is responsible for the electrical communication of information from the axon hillock, through the axon, to the terminal buttons. **GRADED POTENTIALA AND THE THRESHOLD OF EXCITATION** - ***A neuron needs to reach a certain threshold of excitatory stimulation at the axon hillock to trigger the cation potential to occur, and thus fire the neuron.*** - This threshold is called the **"threshold of excitation"** - This threshold is met when the excitatory effect reaches between -**55 to -65mV** - This means to trigger the action potential at the axon hillock, the overall net effect of all the graded potentials converging at the axon hillock needs to excitatory. - **The converging graded potentials need to cause the membrane potential to depolarize and shift from -70mV to a more positive -55 to -65mV** **THE ACTION POTENTIAL: DEPOLARISATION, REPOLARISATION AND HYPERPOLARASIATION** - one way to understand an action potential is to graph the changes in membrane potential which occur during the 'firing of a neuron. - When the membrane potential does reach the threshold of excitation, it will trigger different ion channels in the membrane to open, and at different times, to allow for concentrations of positively and negatively charged ions move across the membrane changing the membrane potential over time. - Looking at the graph we can see that have the threshold of excitation is reached (-55mV), it triggers an action potential which causes a massive **depolarization** of the membrane potential, where it moves from a very negative charge, through to zero charge, and momentarily changing to have a positive charge (+40mV). - Eventually though, the opening and closing of different ion channels will cause the ions to begin to return to their normal state, and there is **re-polarization** of the charge back towards the resting membrane potential of -70mV. - At certain points in time, the cell will become **hyperpolarized,** meaning that it will become even more negative than the resting membrane potential of -70mV, - After a few moments of being hyperpolarized, the membrane potential will return to its **"resting state"** with a membrane potential of -70mV **THE REFRACTORY PERIOD** - Before the membrane potential returns to -70mV, there is a short period of temporary hyperpolarization called the **"refractory period"** - During the refractory period, the ion channels in the membrane become unable to open and allow ions to move across the membrane, no matter how much excitatory stimulation you give them. - This refractory period where ion channels become temporarily unable to open is important, because it ensures an action potential can only flow in one direction along an axon. This is because an action potential is something that spreads. If you provide enough excitation to reach the thresholds of excitation, an action potential will trigger and cause the membrane potential to depolarize in adjacent locations of the cell membrane. - The depolarization phase of an action potential forms the excitatory stimulation needed to trigger an action potential to occur in the vicinity of where it began. - These action potentials then trigger an action potential to occur in the next immediate vicinity too. - It is almost like a line of falling dominos -- once one domino falls, it triggers the fall of other dominos in the vicinity, which creates a spreading chain reaction of falling dominos - Once an action potential begins, it will continue to trigger further action potentials because it acts as the depolarizing stimulus for other area of the cell membrane around it **THE REFRACTORY PERIOD CONTINUED** - The spreading activation caused by an action potential is why it is so important that there is a refractory period following the repolarizing phase of an action potential. - The refractory period means the action potential cannot trigger itself backwards and can instead only transmit a signal one way. - Specially, the direction which an action potential flows is from the axon hillock, down the axon, towards the terminal buttons. - Staying with our domino example, the refractory period is kind of like the period after a domino has been knocked down in one direction, as you can't cause something that is lying down in the opposite direction. **ACTION POTENTIALS OCCUR AT THE NODES OF RANVIER** - The nodes of Ranvier are where the action potential occurs - It first starts at the axon hillock and then it passively conducts the stimulation down the axon - The passive conductance is insulated by the myelin along the axon - But after passively being conducted under the myelin, the excitatory stimulus will pop its head up at the first node od 5. **[STEP C OF NEURAL COMMUNICATION]** **[TRANSMISSION OF CHEMICAL INFORMATION BETWEEN NEURONS]** - **chemical communication** occurs between neurons at the synapse (the small gap between terminal buttons of one neuron and the dendrite or cell body of the next neuron) - This process is part of step C in neuronal communication **SYNAPSE AND KEY STRUCTURES** - **Synapse (also called synaptic cleft)** is the tiny gap between neurons where chemical communication happens - **Pre-synaptic neuron** is the neuron **sending the signal** before the synapse - **Post-synaptic neuron** is the **receiving** the signal (after the synapse) - **Neurotransmitter (NTs)** are specialized chemicals realized from the pre-synaptic neuron into the synapse and slows communication between neurons by binding to receptors in the **post-synaptic neuron** -  **Synaptic vesicles** contain neurotransmitter; will descend the terminal button and fuse with the cell membrane to release neurotransmitters into the synapse **STEP C IN DETAIL: RELEASE OF NEUROTRANSMITTERS** **Neurotransmitter synthesis:** - Created in the neuron (mostly in the cell body but can be produced anywhere) - Stored in synaptic vesicles within the terminal button **Action potential trigger:** - The electrical signal (action potential) moves down the axon to the terminal button - This causes the synaptic vesicles to move toward the cell membrane of the terminal button **Neurotransmitter realize:** - Vesicles merge with the cell membrane, realizing neurotransmitter into the synapse - Neurotransmitter travel across the synapse and bind to receptors on the post-synaptic neuron **THE LOCK AND KEY PRINCIPLE** - Transmission from electrical to chemical communication occurs when neurotransmitters are released into the synapse - There is no direct contact between pre-synaptic and post-synaptic neurons - Communication requires neurotransmitter to move across the synapse and bind to receptors on the post-synaptic neuron **Specificity of binding** - Binding is highly specific, not random - Neurotransmitter bind to receptor sites that match their molecular structure (e.g. dopamine binds only to dopamine receptors) **Lock-and-key analogy** *Neurotransmitter = key* *Receptor = lock* *Only the correct "key" fits the "lock"* **Process of binding** 1. Neurotransmitter released into synapse from vesicles 2. It moves randomly through the extrasellar space (not-goal-directed) 3. Binding occurs only if: a. The neurotransmitter encounters the post-synaptic neuron b. It finds a matching receptor c. The receptor is not already occupying **Implications of randomness:** - **Chemical communication is slower than electrical communication** - Multiple conditions must align for successful binding - Presence of the neurotransmitter - Encounter with the matching receptor - Availability of the receptor site **TO FIRE OR NOT TO FIRE -- NEUROTRANSMITTER - RECPTOR BINDING** - Neurons receive excitatory (EPSPs) or inhibitory (IPSPs) potentials - **Excitatory inputs= depolarization (closer to firing threshold)** - **Inhibitory inputs= hyperpolarization (further from firing threshold)** **Action at Synapse:** - Neurotransmitter bind to post-synaptic receptors, causing **EPSPs or IPSPs** - Binding opens ion channels, altering the ion concentration within the neuron - **Positive ions = depolarization (EPSP)** - **Negative ions = hyperpolarization (IPSP)** - These potentials determine whether the neuron will reach the action potential threshold **Feedback mechanisms:** - Some neurotransmitters bind to **pre-synaptic receptors** to regulate their realize, acting as a feedback loop. **Cyclical Communication** - Neural communication is a cycle: A. Excitatory/inhibitory graded potentials occur in dendrite and soma B. Action potential triggered if threshold is met at axon hillock C. Neurotransmitter realize into the synapse to influence the next neuron - This process repeats neuron-to-neuron **CLEARING THE SYNAPSE** - **Importance of clearing excess neurotransmitter:** continuous neurotransmitter release requires mechanisms to clear the synapse - **Mechanisms of clearing:** 1. **Re-uptake:** pre-synaptic neuron reabsorbs neurotransmitter for reuse 2. **Enzymatic breakdown:** enzymes in the synapse degrade neurotransmitters 3. **Diffusion:** excess neurotransmitters float away into the brain **BALANCE OF EXCITORY AND INHIBITORY SIGNALS** **Excitatory signals:** - allow transmission of signals through firing neurons - essential for communication and information flow **inhibitory signals:** - prevent excessive neuronal firing - essential for balance and preventing uncontrollable excitation (e.g. seizures) - example: seizures result from failure of inhibitory mechanisms **brain health:** - proper brain function depends on a balance of excitor and inhibitory inputs **NEUROTRANSMITTERS OVERVIEW** 1. **GLUTAMATE** - **primary excitor neurotransmitter** - key roles: - learning and memory - synaptic strengthening through long-term potentiation - implicated in **epilepsy** and seizures (uncontrolled excitation) **GABA (gamma-aminobutyric acid)** - **primary inhibitory neurotransmitter** - key roles: - prevents overexcitation in the brain - influenced by: - alcohol (binds to GABA receptors, causing inhibition) - anxiolytics (e.g. valium, Xanax, reduce anxiety by enhancing GABA activity) - anesthetics (suppress nervous system by acting on GABA) - overactivation of GABA can shut down brain activity (e.g. alcohol overdose) **DOPAMINE** - involved **in reward, motivation, emotion, arousal, and movement** - key disorders: - schizophrenia (too much dopamine) - Parkinson's disease (too little dopamine) - complications of treatment: - increasing dopamine for parkin's may induce psychosis - decreasing dopamine for schizophrenia may induce motor symptoms **SEROTONIN** - regulates **mood, sleep and arousal** - **linked to:** - **depression (low levels)**