Biology of Mind Lecture Notes (PDF)

Biology of the Mind Dr. Maureen Vincent 111- 23  Lecture Overview Everything psychological is biological Neural and Hormonal Systems The Cerebral Cortex Tools of Discovery  Biology, Behavior, and Mind Every psychological process is biological Your every idea, every moo...

Biology of the Mind Dr. Maureen Vincent 111- 23  Lecture Overview Everything psychological is biological Neural and Hormonal Systems The Cerebral Cortex Tools of Discovery  Biology, Behavior, and Mind Every psychological process is biological Your every idea, every mood, every urge you have involves biology You love, laugh and cry – but all of these involve your body (your biology) Without your body (your genes, your brain, your appearance) – you are a nobody! Although we discuss biological and psychological influences separately, we always need to remind ourselves of the following: To think, feel or act – always requires biology! Biology, Behavior, and Mind Factors that interact to influence behavior: Biological Psychological & Social-cultural factors BIOPSYCHOSOCIAL APPROACH Neural Communication Neural Communication Nerve cells are called neurons Millions of neurons join in chain-like formation to form the building blocks of the human nervous system Our body and our brain communicate with each other via the nervous system  The Structure of a Neuron Damaged Myelin Sheath Multiple sclerosis - slowing down of the communication of impulses to muscles Results: loss of motor control or coordination  The Structure of a Neuron Parts of the Neuron Functions Dendrites where information comes in Cell body & nucleus life center Axon messages pass down Myelin sheath protects axon and speeds up messages Terminal branches information goes out The Neural Impulse Neurons transmit messages when triggered by chemical signals from neighboring neurons. In response, a neuron fires an impulse Neural Impulse – (or action potential) - a brief electrical charge that travels down its axon Neural transmission How Neurons Communicate Action potential occurs when a neuron sends a message from the cell body down the axon. At the end of the axon - release neurotransmitters from sacs called vesicles Neurotransmitters = chemicals Neurotransmitters cross the synaptic gap and bind to the receptors on the receiving neuron E How Neurotransmitters Influence Us Neurotransmitters - influence behavior and emotions Hundreds of different neurotransmitters  How Neurotransmitters Influence Us Serotonin affects mood, Low Levels in the CNS = Depression hunger, sleep, and High levels = Mania: (talkativeness, euphoria, and risky arousal behaviors (excess spending, increased sexual activity) Dopamine influences High levels in the frontal lobes = Schizophrenia (hear voices, movement, have delusions or false beliefs etc.) learning, attention, and emotion Low Levels in CNS = Parkinson’s disease Uncontrollable muscle tremors decreased mobility Acetylcholine affects muscle action, Low levels: Alzheimer’s disease - a neurodegenerative disorder learning and memory characterized by learning and memory impairments. It is associated with a lack of acetylcholine in certain regions of the brain  How Drugs Alter Neurotransmission Drugs can affect neurotransmission in 2 ways: AGONIST ANTAGONIST Mimics (increases) a neurotransmitter’s inhibits or blocks a neurotransmitter’s action action Drug is similar to neurotransmitter The drug is not similar enough to mimic its effects Used when body is NOT producing enough Used when the body is producing TOO of a neurotransmitter MUCH of a particular neurotransmitter Example: Lack of serotonin - depression Example: Too much dopamine – Schizophrenia (hearing voices, have delusions etc)  THE NERVOUS SYSTEM  The Nervous System Nervous system electrochemical communication network consists of all the nerve cells of the central nervous system and peripheral nervous system Central nervous system (CNS) Consists of the Brain and spinal cord Peripheral nervous system (PNS) Consists of: Sensory & motor neurons connecting the CNS to the rest of the body  The Nervous System Interneurons are present only in the CNS Central nervous system (CNS) The CNS consists of the spinal cord and brain CNS - does bulk of the functions The brain is the control center and the spinal cord is the major highway to and from the brain. Interneurons enable communication between: sensory neurons and the brain & motor neurons and the brain  The Nervous System Functions Types of Neurons carry messages from the body’s sensory receptors to the Sensory CNS (brain and spinal cord) for processing carry instructions from the CNS (brain and spinal cord) to Motor the body allow internal communication between sensory neurons Interneurons and the brain as well as the brain and motor neurons Interneurons are only in the CNS  Interneurons only in the CNS (Spinal Cord and Brain) – message can travel up and down (SEE RED IN DIAGRAM) = Sensory and motor neurons Sensory neurons Motor neurons deliver the deliver the message to message from the spinal cord the brain- spinal and up to brain cord to execute a (for the most motor function part) e.g. move hand e.g. pick up hot coal, signal from the sensory neurons in your fingertip would travel to interneurons in your spinal cord Then some of these interneurons would signal to the motor neurons controlling your finger muscles to let go, while others would transmit the signal up the spinal cord in the brain, where it would perceive pain  Interneurons Are the most numerous class of neurons Are involved in processing information For e.g. it would be combinations of interneurons in your brain that would allow you to: draw the conclusion that things that looked like hot coals weren’t good to pick up and Hopefully retain that information for Interneuron future reference Three different types of neurons Peripheral Consists of Sensory Nervous and Motor neurons System Sensory Motor Neurons Neurons  The Peripheral Nervous System (PNS) PNS has two components: Somatic nervous system - controls voluntary muscle movements e.g. scratch your nose, running etc. Autonomic nervous system - controls glands and muscles in internal organs autonomously e.g. heartbeat, breathing  Peripheral Nervous System (PNS) Autonomic nervous system - serves two important functions: sympathetic nervous system - arouses and expends energy parasympathetic nervous system - conserve energy as it calms you. The sympathetic and parasympathetic nervous systems work together to keep us in a steady internal state called homeostasis  The Endocrine System Body’s Second Communication system Endocrine system is set of glands that secrete hormones into the bloodstream Hormones travel through the body and affect tissues including the brain.  EXAMPLE: Being Attacked A stressful event triggers your hypothalamus to instruct your pituitary to release a neurohormone that causes your adrenal glands to flood your body with adrenaline (a stress hormone that increases The Endocrine heart rate and prepares you to deal with the stressor) System The Endocrine System Estrogen Estrogen Oestrogen The Brain PHRENOLOGY Joseph Gall 1796  PHRENOLOGY Joseph Gall (1796) developed the idea that the shape of our heads is a window into our personalities. Phrenologists believed the brain was comprised of separate “organs” responsible for different aspects of the mind, such as for self-esteem, cautiousness and the desire to do good. They also thought of the brain like a muscle – the more you used a particular organ the more it would grow in size, and less used faculties would shrink. The skull would then mould to accommodate these peaks and troughs in the brain’s surface – providing an indirect reflection of the brain, and thus, the dominant features of a person’s character. The theory was called into disrepute. The Cerebral Cortex  The cerebral 1.Cerebral cortex is the cortex outermost layer of the brain, made up primarily of folded grey matter 2.The cerebral cortex has two hemispheres. 3.  Hemisphere Specialization OR 4. I AM……. Brain Lateralization The left hemisphere controls the right- hand side of the body and receives information from the right visual field, controlling speech, language, and recognition of words, letters, and numbers. The right hemisphere controls the left- hand side of the body and receives information from the left visual field controlling creativity, context, and recognition of faces, places, patterns and objects.  Has been disputed as Pop Psychology or Pseudoscience Not that clear cut- e.g. I am left brained or right brained 5. Corpus Callosum The Cerebral Cortex The two hemispheres are connected by the corpus callosum. Corpus callosum - a large band of neural axon fiber. Each hemisphere controls the opposite side of the body Without the corpus callosum, the right and left side of the body do not work together The Cerebral Cortex 6. Split brain surgery Also called a corpus callosotomy Used for severe epilepsy (when medication fails) Isolates the brain’s two hemispheres by cutting the fibers of the corpus callosum  Split-brain surgery is a drastic way of alleviating epileptic seizures, the occurrence of sporadic electrical storms in the brain. The procedure involves severing the corpus callosum, the main bond between the brain's left and right hemispheres Effects of Split-Brain surgery Good news: Seizures significantly reduce or cease Negative effect: The two hemispheres almost seem to function independently After the right and left brain are separated, each hemisphere will have its own separate perception, concepts, and impulses to act. Having two "brains" in one body can create some interesting dilemmas. “In the first months after her surgery, Vicki found that when shopping for groceries, she would look at an item on the shelf and know that she wanted to place it in her trolley — but she couldn't. “I'd reach with my right hand for the thing I wanted, but the left hand would come in and they'd kind of fight, like repelling magnets.” Getting dressed posed a similar challenge: Vicki couldn't reconcile what she wanted to put on with what her hands were doing. Sometimes she ended up wearing three outfits at once. “I'd have to dump all the clothes on the bed, catch my breath and start again.”  Roger Sperry Received Nobel Peace Prize in 1981 on Medicine for his split-brain research Discovered: functional specialization or lateralization of the brain – More specifically, he discovered the left hemisphere was responsible for language, understanding and articulation While the right hemisphere could recognize a word, it could not articulate (say) the word  SPERRY NON-SPLIT BRAIN PATIENT The typical brain- Cover right eye. Look at key with the left eye Information travels to back of brain (green line) and then crosses the corpus callosum to the LEFT hemisphere where verbal content is analyzed, and language is produced Language is found in the LEFT HEMISPHERE – so person can say it is a key  In the SPLIT BRAIN Cover right eye Look at key with left eye Information travels to the back of brain (green line), but message CANNOT cross to LEFT SPERRY hemisphere (language centre) as there is no corpus callosum – so SPLIT-BRAIN person knows what the object is PATIENTS but cannot SAY it (key)  Sperry found evidence for hemisphere specialization or brain laterization When split-brain patients are shown an image only in the left half of each eye’s visual field, they cannot vocally name or SAY what they have seen. This is because the image seen in the left visual field is sent only to the right side of the brain, and the speech-control center is on the left side of the brain. Communication between the two sides is inhibited, so the patient cannot say out loud the name which the right side of the brain is seeing The Brain stem- consciousness, breathing , heart rate – involuntary processes, as well as posture, balance and coordination of movement Located in forward part of brain, Located behind the frontal extending back lobe Located at the back of the brain) Located on the side of the head) 7. LOBES OF THE BRAIN Now, let’s discuss each lobe and their functions  FRONTAL LOBE It contains the motor cortex, which is involved in planning and coordinating movement The frontal lobes are the largest lobes in (electrical stimulation the human brain and of motor cortex causes a part of the body to they are also the move) most common region of injury in traumatic brain injury the prefrontal cortex, which is responsible for higher-level Broca’s area, which cognitive The frontal lobes are is essential for functioning involved in reasoning, language production motor control, emotion, and language (speech production) Frontal Lobe – another view  PRIMARY CORTEX Primary motor cortex - this strip is in charge of voluntary movements like waving goodbye, wiggling your eyebrows, and kissing. It is an excellent example of the way that the various regions of the brain are highly specialized. CORTEX  Interestingly, each of our various body parts has a unique portion of the primary motor cortex devoted to it Primary Motor Cortex For example, each individual finger has about as much dedicated brain space as your entire leg. Your lips, in turn, require about as much brain processing as all of your fingers and your hand combined!  Located: in the Development: one of the slowest parts of frontal lobe, the the brain to develop, reaching full maturity in part of our brain our mid-twenties at the very front of our head Explains why children and teenagers are more prone to risk-taking behaviour, while adults are generally better at planning ahead and reasoning Functions: involved in executive functions, or the higher cognitive functions and include memory, attention, flexibility, planning, reasoning, problem solving. e.g. decision making - allows to consider past events and experiences in order to make the best choices. e.g. plays a role in short term memory Damage: display difficulties with executive functions such as memory and attention. Also cause personality It also affects things like holding changes, abnormal emotional responses, and difficulty in conversations, reasoning, self-monitoring functioning in daily life (e.g. Phineas Gage -1800’s) and time management Phineas Gage Brain injury led to new discoveries in neuroscience  Phineas Gage (1823-1860) Suffered a traumatic brain injury when an iron rod was driven through his entire skull, destroying much of his prefrontal lobe. Also, lost vision in his eye. Before accident: hardworking and a pleasant man. A shrewd and smart businessman, very energetic and focused After accident: His personality had changed – his mind had radically changed. Now - aggressive drunkard unable to hold down a job Injury lead to an inability to suppress impulses, regulate emotions and a loss of social inhibition, lead Gage to behave in inappropriate ways. Problems in emotional processing and rational decision making. Belief – Gage’s personality had changed because of damage to prefrontal lobe. Lead to belief: different parts of the brain are responsible for different functions. Visual representation of rod – piercing through the back of Gage’s left eye socket and out of his frontal lobe  Whether Phineas Gage had a change of personality based on damage to Prefrontal cortex is debated by some. Model in a Nevertheless, this case led to new scientific discoveries that different museum parts of the cerebral cortex are responsible for different functions  PARIETAL LOBE Located immediately It contains the behind the frontal lobe, somatosensory is involved in cortex processing which is information from essential for the body’s senses processing sensory information from across the body, such as touch, temperature, and pain Essential If you electrically stimulate the somatosensory cortex – the person will report feeling a part of their body being touched The somatosensory cortex is a part of your brain that receives and processes sensory information from the entire body Somatosensory cortex Primary motor cortex sends receives information from messages to various parts of various parts parts of the body the body to move TEMPORAL LOBE The temporal lobe is located on the side of the head (temporal means “near the temples”) and is associated with hearing, memory, emotion, and some aspects of language. It contains the Primary auditory cortex, the main area responsible for processing auditory information.  LANGUAGE & the TEMPORAL LOBE There are two parts of the brain located in the temporal lobe that are responsible for language: 1. Broca’s area 2. Wernicke’s area. Broca’s area is responsible for speaking, reading and writing words and numbers. Aphasia in this area of the brain is often called non-fluent aphasia or expressive aphasia, because the individual has lost the ability to speak words or sentences, although the ability to understand language has not been affected. The patient will struggle to find the right word or number, and not be successful. Wernicke’s area is responsible for understanding words and numbers. Aphasia in this area of the brain is often called fluent aphasia or sensory aphasia, because although the individual can speak using mostly normal words, they are often nonsensical – as if the words’ meanings had been re-arranged. The person speaking has no idea they aren’t using language correctly and will often be shocked when later presented with a recording of their conversation. They also cannot understand what anyone else is saying to them  OCCIPITAL LOBE Located at the back of the brain contains the primary visual cortex, which is responsible for interpreting incoming visual information  Deficits if a lobe is damaged Frontal lobe: Weakness (motor abilities) Inattentiveness, concentration problems Personality disorders Language – speech production Memory and behaviour problems Parietal lobe: Disorientation of environment/space (difficulty finding their way around new, or familiar places) Inability to recognise self Temporal lobe: Hearing deficits, Deafness Memory (pictures, words, names) Speech comprehension problems Cerebral cortex dysfunction can be due to tumours, trauma, infections, autoimmune Occipital lobe: Visual deficits diseases, accidents complete blindness or colour blindness 8. ASSOCIATION AREAS The Cerebral Cortex Has association areas in all 4 lobes Involved in more complex functioning e.g. Rather than Association area – receives input seeing simple contours, from multiple areas edges (or sensory qualities like color or pitch) – you can Involved in organizing information recognize actual objects – that comes from other parts of the brain trees, car, horse, bike Association Areas are responsible for more complex actions Brings meaning to what you hear and smell, facial recognition, etc For e.g. Temporal Lobe: For rather than just EXAMPLE hearing the pitch or sound, the association area brings meaning to this e.g. allows you to recognize a song Humans - association areas are by far the most developed part of the cerebral cortex, and the brain in general Association areas take up an increasingly larger percentage of the cerebral cortex as brain size increases among different species  Chimpanzee Human Association function of the cortex The Cerebral Cortex More complex animals have more cortical space devoted to integrating/associating information (higher level processes)  EXAM Lobes of the Brain Cortex in each lobe And other relevant structures FUNCTIONS  Functions of the Lobes PARIETAL FRONTAL Sensation (touch) Much of the parietal Problem Solving lobe is dedicated to Reasoning (judgement) receiving and Planning processing their input Thinking Regulation of emotion The fingers and (how you respond) hands are a primary Movement site for sensory data. Decision making Comprehension Body Awareness Memory Personality OCCIPITAL Vision TEMPORAL Auditory processing (Hearing) Color Perception Memory Speech comprehension Smell Facial Recognition BRAIN PLASTICITY  BELIEF: BRAIN DOES NOT CHANGE FIXED STRUCTURE But, we now know The brain is a river, not a rock – it is continually changing Plasticity: Brain’s ability to modify itself after some type of damage and create new pathways  The Brain’s plasticity Plasticity refers to the brain’s ability to reorganize neural pathways throughout the lifespan as a result of experience The Brain can mend itself by: making new connections with neighboring neurons (synaptogenesis) to move around the damaged area forming new neurons through neurogenesis Young children—very resilient (as have heaps of neurons) – compared to adults. Plasticity diminishes later in life  EXAMPLES e.g. If a blind person uses one finger to read Braille - - - the area dedicated to that finger expands Also, in a blind person, sense of touch will take over the part of brain normally used for sight 10. TOOLS OF DISCOVERY  Examining the brain Lesions (surgical destruction on parts of the brain) performed on animals have yielded some insights about less complex brain structures. No longer necessary, as we now use other methods to get information about the brain Methods of investigation Methods of investigation EEG (Electroencephalogram) PET (Positron emission tomography) MRI (Magnetic resonance imaging) fMRI (Functional MRI) EEG  PET SCAN allows us to see what part of the brain is active by tracing where a radioactive form of glucose goes while the brain performs a given task  MRI uses a magnetic field and radio waves to take cross sectional pictures of your body. Used to investigate or diagnose conditions that affect soft tissue such as tumours or brain disorders Functional MRI (fMRI) reveals brain activity and function rather than structures Measures brain activity by detecting changes associated with blood flow. When an area of the brain is in use, blood flow to that region also increases FUNCTIONAL MRI fMRI  Recent tools to investigate the brain Tools Description EEG records electrical activity in brain PET what part of the brain is active by tracing where glucose goes while the brain performs a task MRI makes images of the brain tissue using magnets – looks at structures of the brain fMRI reveals brain activity and function rather than structures THE END