PYB102 - The Mind and the Brain Study Notes PDF

**PYB102 -- The Mind and the Brain** **Study Notes** **Anne Vas** **Exam: November 14^th^ 2024** **\ ** **Central Nervous System (CNS) and Peripheral Nervous System (PNS)** **Key Knowledge** 1. **Axon**: - Transmits signals away from the neuron's cell body (soma) to communicat...

**PYB102 -- The Mind and the Brain** **Study Notes** **Anne Vas** **Exam: November 14^th^ 2024** **\ ** **Central Nervous System (CNS) and Peripheral Nervous System (PNS)** **Key Knowledge** 1. **Axon**: - Transmits signals away from the neuron's cell body (soma) to communicate with other neurons or muscles. 2. **Tracts vs. Nerves**: - **Tracts** (in the CNS): Bundles of axons transmitting signals within the CNS. - **Nerves** (in the PNS): Bundles of axons transmitting signals outside the CNS. 3. **Nuclei vs. Ganglia**: - **Nuclei** (in the CNS): Clusters of neuron cell bodies associated with specific functions, e.g., processing sensory or motor information. - **Ganglia** (in the PNS): Similar clusters in the PNS, typically involved in sensory or autonomic functions. **Central Nervous System (CNS)** **Neuroanatomical Directions** 1. **Ventral**: Towards the belly. 2. **Dorsal**: Away from the belly (towards the back). 3. **Anterior (Rostral)**: Toward the front (nose). 4. **Posterior (Caudal)**: Toward the back of the head (tail). 5. **Medial**: Toward the spine or midline. 6. **Lateral**: Away from the midline. **Neuroanatomical Planes of View** 1. **Sagittal (Medial)**: Cuts the brain into left and right sides, useful for viewing structures like the corpus callosum. 2. **Coronal**: Cuts the brain into front (anterior) and back (posterior) sections. 3. **Horizontal**: Cuts the brain into top and bottom sections. **Divisions of the Brain** 1. **Forebrain**: - **Telencephalon**: - **Cerebral Cortex**: Involved in higher-level functions like thought, reasoning, sensation, and voluntary muscle movement. - **Limbic System**: Involved in emotion, memory formation, and motivation. Key structures include: - **Amygdala**: Processes emotions and fear responses. - **Hippocampus**: Critical for memory formation and spatial navigation. - **Basal Ganglia**: Plays a major role in movement control and planning. - **Diencephalon**: - **Thalamus**: Relay station for sensory information (except smell), filtering and organizing inputs before passing them to the cerebral cortex. - **Hypothalamus**: Regulates basic drives (e.g., hunger, thirst, sex) and controls the autonomic nervous system, influencing functions like body temperature and fight-or-flight responses. A diagram of the brain Description automatically generated 2. **Midbrain**: - **Superior Colliculi**: Relay and process visual information, crucial for visual attention. - **Inferior Colliculi**: Relay and process auditory information, essential for auditory attention. 3. **Hindbrain**: - **Medulla**: - Controls **essential autonomic functions** necessary for survival, e.g. - Heart rate - Blood pressure - Respiration - **Pons**: - Acts as a **bridge** between different brain regions - Contains nuclei that regulate: - **consciousness** and alertness including the reticular formation. - **Cerebellum**: - Coordinates voluntary movements, balance, and posture. - Not contralaterally organized (i.e., left side controls left, and right controls right). Midbrain Hindbrain **Brain Development** - Divisions originate from the earliest stages of development of the nervous system in the ectoderm. - Neural tube grows to form the central nervous system. - Developing neural tube begins to form discrete enlargements or vesicles. - Embryonic vesicles develop into the major regions of the brain: forebrain, midbrain, hindbrain.  **Lobes of the Cerebral Cortex** 1. **Occipital Lobe**: Primarily responsible for vision, including processing visual information and forming visual perceptions. 2. **Parietal Lobe**: Processes sensory information related to touch, pressure, temperature, and pain. 3. **Temporal Lobe**: Key for processing auditory information, memory formation, and some aspects of language. 4. **Frontal Lobe**: Involved in complex processes like reasoning, planning, movement, speech, and problem-solving. **Important Concepts** 1. **Lateralisation (Specialisation)**: - Left cerebral hemisphere is lateralised for language. 2. **Contralateral Arrangement**: - Left hemisphere processes somatosensory stimuli from the right side. - Visual stimuli from the left visual field projected to the right hemisphere. - Right hemisphere processes somatosensory stimuli from the left side. - Visual stimuli from the right visual field projected to the left hemisphere. **The Split-Brain Experiments** - Patients with severe epilepsy had their corpus callosum severed to stop disconnected activity. - Optic chiasm remained joined. - Used to investigate the lateralisation of the cerebral hemispheres. - Left hemisphere more specialised for language. - Right hemisphere more specialised for motor control with left limbs. - Successful, but caused unusual behaviour (e.g., right hand grabbing a coat while left hand put it back). **Cerebral Ventricles** - Series of chambers in the brain filled with cerebrospinal fluid (CSF); form the ventricular system. - CSF produced by the choroid plexus. - Functions: - Shock absorber; protects the brain from sudden movements by floating in CSF. - Medium for exchange. **Brain Support Systems** - **Meninges**: - Protective sheaths around brain and spinal cord. - Three layers: - **Dura Mater (hard):** Closest to surface of the skull. - **Arachnoid membrane:** Contains subarachnoid space filled with CSF. - **Pia Mater (soft):** Closest to the surface, follows the bulges and grooves of the cerebral cortex. - Shock absorbing. A diagram of a brain Description automatically generated - **Blood Supply**: - Blood-brain barrier: Protects the brain from harmful substances. - Brain capillaries (blood vessels): Maintain the barrier. **Spinal Cord** 1. Distributes motor signals from the brain to the muscles. 2. Collects somatosensory information. - Protected by the **vertebral column**, passing through holes in each vertebra. - Spinal cord is about two-thirds of the length of the vertebral column. - Rest of the space filled by a mass of spinal nerves (cauda equina). - **White matter on the outside, grey matter on the inside.** **Peripheral Nervous System (PNS)** **Divisions of the PNS** 1. **Somatic Nervous System**: - **Spinal Nerves**: - Fusion of two distinct branches (roots). - Begin at the junction of dorsal and ventral roots of the spinal cord. - Nerves leave the vertebral column to travel to muscles or sensory receptors. - **Afferent Axons (arrive at spinal cord)**: Dorsal pathway, sensory information towards CNS. - **Efferent Axons (exit spinal cord)**: Ventral pathway, motor commands away from CNS. - **Cranial Nerves** (do not learn the details): - 12 nerves attached to the ventral surface. - Control many senses in the body; most serve sensory and motor functions from the head and neck region. - The tenth, **Vagus Nerve**, regulates the functions of organs in the thoracic and abdominal cavities. 2. **Autonomic Nervous System**: - Serves basic life functions: - Heart beating. - Response to stress. - Regulation of smooth muscle (skin, blood vessels, gut walls). - Regulation of cardiac muscles and glands. - Two anatomically separate systems: - **Sympathetic System**: - Expenditure of energy from body reserves. - Prepares the body in response to threats. - [Fight-or-flight response] - **Parasympathetic System**: - Increases the body\'s supply of stored energy. - Calms the body down. - Restores energy - [Rest and digest.]  **Neurons - Cells in the Human Nervous System** **Neurons** - **Basic functional units of the nervous system**: - Neurons do not touch each other; the gap is called the synapse (or synaptic cleft). - The neuron transmitting information is the **presynaptic neuron**. - The neuron receiving information is the **postsynaptic neuron**. - **Functions**: - **Reception**: Take in information from other neurons. - **Conduction**: Integrate those signals. - **Transmission**: Pass signals to other neurons. **Glial Cells** - **Support Functions**: - Nourish, protect, and physically support neurons. - Critical in brain development. - **Oligodendrocytes**: - A type of glial cell that covers the axons of neurons with myelin, which is critical for effective functioning. **Parts of the Neuron** - **Dendrites**: - Receive messages from other neurons. - Transmit information to the soma. - **Soma (Cell Body)**: - Contains mechanisms that control metabolism and maintenance of the cell. - Collates messages from other neurons. - **Axons**: - Carry messages away from the soma towards other cells. - These messages are called action potentials. - **Terminal Buttons**: - Located at the end of the axon branches. - Secrete neurotransmitters that affect the activity of other cells. - **Myelin**: - Insulates some axons to promote efficient transmission of action potentials. - Prevents ion flow across the membrane. - Current can only flow across the membrane at breaks in the myelin (Nodes of Ranvier). - Sodium channels are concentrated at these nodes. - Action potentials can only be generated in these gaps. - The action potential jumps between gaps, massively increasing speed (saltatory conduction). - Non-myelinated axons are much slower as action potentials are generated repeatedly along the axon. A diagram of a nerve cell Description automatically generated **Cell Membrane and Action Potential** - **The Cell Membrane**: - Outer layer composed of a lipid bilayer---two layers of fatty molecules with specialized proteins that float. - Proteins form pores or channels controlling material movement into/out of the cell. - Separates two different chemical solutions; potential difference due to relative concentrations. - At rest (neurons not interacting), pores are closed. - **Resting Membrane Potential**: - Difference in chemical composition (concentration) inside and outside the cell at rest (\~-70 mV). - More Na⁺ outside and more K⁺ inside. - **Action Potential**: - Brief reversal in resting charge of the neuron triggered by the exchange of ions across the neuron membrane. - When the membrane is sufficiently depolarized (resting potential moves towards 0 mV), an action potential is triggered when the depolarization reaches about -55 mV (threshold). - If the threshold level is reached, an action potential of a fixed size will always fire (all-or-nothing principle). - Speed of propagation is determined by: - Diameter of the axon (larger = faster). - Presence or absence of myelin sheath. **Phases of Action Potential** 1. **Resting Membrane Potential (\~-70 mV)**: - The neuron is at rest; the inside is negatively charged compared to the outside. - Sodium (Na⁺) and potassium (K⁺) channels are closed. 2. **Depolarization (0 to 1 msec)**: - Sodium channels open, allowing Na⁺ ions to flow in. - Membrane potential increases, becoming less negative, leading to rapid depolarization (upward slope to +30 mV). 3. **Peak of Action Potential (Around 1 msec)**: - Sodium channels close, stopping Na⁺ influx. - Potassium channels open, allowing K⁺ ions to flow out. 4. **Repolarization (1 to 2 msec)**: - Potassium efflux decreases the membrane potential, moving back towards a negative value. 5. **Hyperpolarization (Around 2 to 3 msec)**: - Potassium channels close slowly, causing the potential to dip below resting potential. 6. **Return to Resting Membrane Potential (3 to 5 msec)**: - The sodium-potassium pump restores the membrane potential to resting state, preparing for the next action potential. **Synaptic Transmission** - Neurons are separated by the synaptic cleft. - When an action potential reaches the terminal buttons, it causes the release of neurotransmitters that travel across the synaptic cleft to be received by dendrites of other neurons. **Steps of Synaptic Transmission** 1. Neurotransmitters are stored in vesicles within the terminal button. 2. The action potential triggers the release of neurotransmitters into the synapse. 3. Neurotransmitters diffuse across the synaptic cleft. 4. Some attach to receptor molecules in the postsynaptic membrane and activate them, generating an action potential. - **Excitatory**: Increases likelihood of action potential by causing slight depolarization. - **Inhibitory**: Decreases likelihood of action potential by causing hyperpolarization. 5. Neurotransmission is terminated by: - Reuptake. - Enzyme deactivation. - Autoreception. **Types of Postsynaptic Potentials** 1. **Excitatory Postsynaptic Potentials (EPSPs)**: - Make the inside of the neuron more positive (depolarization). - Bind to receptors, allowing positive ions (like Na⁺) to enter. - Increase the likelihood of firing an action potential. 2. **Inhibitory Postsynaptic Potentials (IPSPs)**: - Make the inside of the neuron more negative (hyperpolarization). - Bind to receptors, allowing negative ions (like Cl⁻) in or positive ions (like K⁺) out. - Decrease the likelihood of firing an action potential. 3. **Integration of EPSPs and IPSPs**: - Neurons receive both excitatory and inhibitory signals simultaneously. - The neuron sums the effects of all inputs: - More EPSPs than IPSPs can lead to firing. - Strong IPSPs can prevent firing. - This integration helps the neuron decide whether to activate (fire an action potential) or remain inactive. **Basic Processes of Memory** **1. Encoding** - **Definition**: Transform sensory stimuli into a form that can be placed in memory. - **Key Component**: Attention - Acts as a filter for further processing. - Allows one stimulus through the filter while others remain buffered. - **Types of Stimuli**: - Auditory (e.g., AC, voice, key clicking) - Feeling (e.g., clothes, feet in shoes) - **Importance**: Prevents overload in the system. - **Selective Attention**: Determines the quality of encoding. - **Depth of Processing**: - **Maintenance Rehearsal**: Repetition of information without deeper meaning. - **Elaborative Rehearsal**: Meaningful processing of information (e.g., thinking about the material). - **Types**: - Superficial (e.g., Is it written in capitals?) - Phonological (e.g., Does it rhyme with \"mat\"?) - Semantic (e.g., Does it fit into context?) - **Visual Imagery**: Concrete objects are recalled better than abstract items. - **Self-Referent Encoding**: Applying processed information to oneself. **2. Storage** - **Sensory Register**: - Registers and briefly holds information from the senses. - **Types**: - **Iconic Memory**: Visual system. - Duration: \< ½ second. - Capacity: 9-10 items (Sperling, 1960). - **Echoic Memory**: Auditory system. - Duration: \~ 2 seconds. - Capacity: \~ 5 items. - **Sperling\'s Experiment (1960)**: - Explored capacity and duration of sensory memory. - **Whole-Report Task**: Recall all letters; typically 4-5 letters. - **Partial-Report Task**: Cued recall of a specific row; nearly all letters recalled. - **Implications**: - Sensory memory has a large capacity but very short duration. - Attention determines what transfers from sensory to short-term memory. - **Short-Term Memory (STM)**: - Intermediate storage for information before consultation. - **Chunking**: Organizing units of information. - Duration can exceed 20 seconds with rehearsal. - Information is lost through decay and interference. - **Dual-Task Technique**: Memory task combined with a dependent task shows increased latency and constant error rate. - **Working Memory**: - **Components**: - **Phonological Loop**: Manipulation of speech-based information. - **Visuospatial Sketchpad**: Manipulation of visual and spatial images. - **Central Executive**: Supervises and controls the two systems. - **Long-Term Memory (LTM)**: - Storage system that retains information for long periods. - **Characteristics**: Large capacity, long duration, different types. **3. Retrieval** - **Types**: - **Free Recall**: - **Primacy Effect**: Best recall for first items learned. - **Recency Effect**: Good recall for last items (mostly STM). - **Context**: Better memory when in the same context as learning. - **Internal State**: Better memory when internal state matches learning conditions. **Memory by Time and Type** **1. Memory by Duration** - **Multiple Trace Hypothesis**: Classifies memory by duration. - **Iconic Memories**: Briefest duration. - **Short-Term Memories**: Longer duration than iconic. - **Long-Term Memories**: Most enduring, lasting days to years. **2. Memory by Type** - **Nondeclarative (Procedural) Memory**: Knowledge shown by doing; implicit memory. - **Examples**: Grammar, motor skills, problem-solving. - **Types**: 1. Skill Learning (e.g., riding a bike). 2. Priming (e.g., increased likelihood of using a recently heard word). 3. Conditioning (e.g., salivating upon seeing favorite food). - **Declarative Memory**: Knowledge that can be explicitly stated. - **Examples**: Facts, events. - **Types**: 4. Semantic Memory: General knowledge (e.g., best friend\'s birthday). 5. Episodic Memory: Autobiographical memories (e.g., attending a friend\'s party). -  **3. Brain Structures Involved in Memory** - **Study of Brain Damage**: Insights from patients with brain injuries. - **Case Study: Henry Gustav Molaison (HM)**: - Bilateral medial temporal lobectomy due to seizures. - **Post-surgery Effects**: - Preserved perceptual and motor abilities. - Intact short-term memory. - Retrograde Amnesia: Loss of pre-surgery memories. - Severe Anterograde Amnesia: Inability to form new long-term memories. - **Key Finding**: Hippocampus is essential for forming new memories. - **Formal Assessments of HM\'s Amnesia**: - **Digit Span + 1 Test**: Inability to form new long-term verbal memories. - **Block Tapping Memory Span Test**: Indicated inability to form new memories beyond verbal information. - **Mirror Drawing Test**: Performance improved despite lack of memory. - **Incomplete Pictures Test**: Performance improved despite lack of memory. - **Animal Model Attempts**: - Early models failed; lesions in animals did not replicate severe anterograde amnesia. - Development of the Delayed Non-Matching-to-Sample Task tested declarative memory in monkeys. - Findings on brain structure roles in memory formation. **Synaptic Mechanisms of Learning and Memory** - **Neural Mechanisms**: - Focus on structural and physiological changes at synapses. - **Long-Term Potentiation (LTP)**: - Increase in synaptic effectiveness with repeated firing. - TP is essential for forming long-term memories. When you learn something new, the connections in your brain become stronger through LTP, making it easier to remember that information later. - **Stages**: 1. Normal firing rate. 2. High pre-synaptic firing leads to strong post-synaptic firing. 3. Normal pre-synaptic firing but increased post-synaptic firing. - **NMDA Receptor**: - Main excitatory neurotransmitter receptor (glutamate). - Requires simultaneous events for maximal response: 1. Glutamate binding. 2. Partial depolarization of the postsynaptic neuron. **Consciousness and REM Sleep** **1. Electroencephalogram (EEG)** - **Definition**: Measures electrical activity of brain waves. - **Purpose**: Provides insight into mental states (e.g., relaxation, concentration). - **Mechanism**: - Electrodes placed on the scalp detect and measure electrical activity patterns from the brain. - Electrodes amplify electric potentials occurring in brain cells. - **Types of Brain Waves**: - **Beta Waves**: - Frequency: 12-30 Hz - Associated with alertness, active thinking, and concentration. - **Alpha Waves**: - Frequency: 8-12 Hz - Present during relaxed, calm, but awake states (e.g., meditation). - **Theta Waves**: - Frequency: 4-8 Hz - Associated with light sleep and relaxation; present in REM sleep. - **Delta Waves**: - Frequency: 0.5-4 Hz - Dominant in deep sleep (NREM); involved in restorative processes. - **K-Complexes**: - Large, high-amplitude waves observed in NREM sleep; may occur in response to external stimuli. **2. Electrooculogram (EOG)** - **Definition**: Measures electrical activity of eye movements. - **Purpose**: Useful in sleep studies to detect REM (rapid eye movement) sleep (dreaming). - **Applications**: Helps understand attention and eye movement patterns during activities like reading and visual searches. **3. Electromyogram (EMG)** - **Definition**: Measures muscle activity by detecting electrical signals from muscle contractions. - **Purpose**: Assesses muscle tension, indicating physical relaxation or stress. - **Relevance in Sleep**: Essential for determining when muscles are relaxed during sleep. **Sleep Disorders** - **Types**: - **Insomnia**: Difficulty in falling or staying asleep. - **Sleep Apnea**: Breathing interruptions during sleep. - **Somnambulism (Sleepwalking)**: Engaging in activities while asleep. - **Night Terrors**: Intense fear episodes during sleep. - **REM Sleep Behaviour Disorder**: Acting out dreams during REM sleep. - **Narcolepsy**: Excessive daytime sleepiness and sudden sleep attacks. **Brain Regions Involved in Sleep Regulation** - **Suprachiasmatic Nucleus (SCN)**: - Located in the hypothalamus; the \"master clock\" regulating circadian rhythms. - Responds to light signals from the retina to synchronize the body's internal clock. - **Retina and Optic Nerve**: - Detect light and send signals to the SCN to influence wakefulness and sleepiness. - **Hypothalamus**: - Controls various functions, including sleep, hunger, and body temperature. - **Pineal Gland**: - Produces melatonin, which induces sleep; regulated by light exposure. - **Pons**: - Crucial for regulating REM sleep; sends signals to inhibit motor neurons during REM to prevent acting out dreams. - **Thalamus**: - Acts as a sensory relay station and is involved in transitioning between wakefulness and sleep. - **Lateral Geniculate Nucleus (LGN)**: - Relays visual information to the visual cortex; involved in visual processing during REM sleep. **Key Processes** - **Circadian Regulation**: - Light enters through the eyes, signaling the SCN to adjust circadian rhythms. - The SCN communicates with the pineal gland to regulate melatonin production. - During REM sleep, the pons and other regions coordinate eye movement and muscle atonia (temporary paralysis). - **Impact of Visual Impairment**: - Visual impairment from birth can disrupt circadian rhythms, leading to irregular sleep patterns. - Individuals who lose sight later may retain some circadian regulation based on prior light exposure. **Summary** - The brain utilizes light cues to regulate the sleep-wake cycle (circadian rhythm) via the SCN and pineal gland. - During REM sleep, the pons manages eye movement and muscle paralysis, while the thalamus and other regions process sensory information.  A graph of ecg Description automatically generated **Emotion and Stress** **Emotion** - **Traditional Basic Emotion Approach:** - Suggests a definitive number of emotions. - **6 Most Common Universal Emotions:** Surprise, Anger, Fear, Sadness, Disgust, Happiness. - Limited agreement on the total number of emotions. - Capable of expressing 6 basic emotions in universally recognizable ways. - **Emotion vs. Mood:** - **Emotions:** Short-term, transient, intense responses to specific events. - **Mood:** Persistent state, less intense, and less specific than emotions. **Theories of Emotion** - **James-Lange Theory of Emotion:** - Emotions are caused by bodily responses. - Sequence of events: 1. **Event or Stimulus:** Encounter a stimulus (e.g., seeing a snake). 2. **Physiological Response:** Physical changes occur (e.g., increased heart rate, trembling). 3. **Emotion:** Perception of these changes leads to the experience of emotion (e.g., \"I feel afraid because I am trembling\"). - **Facial Feedback Hypothesis:** - Participants split into two groups: 4. Watch cartoons with a pencil between teeth (imitating smiling). 5. Watch cartoons with a pencil held between the lip and nose (imitating frowning). - Findings: 1. Those with the pencil between their teeth rated cartoons as funnier, suggesting the physiological state of smiling may enhance emotional experience. - **Cannon\'s Criticism of James-Lange Theory:** 1. Autonomic responses are slow; we experience emotion before physiological changes. 2. Severing visceral nerves had no effect on emotions in rats. 3. Many emotional states link to the same visceral responses. 4. Injecting adrenaline does not induce specific emotional feelings. - **Schachter-Singer Two-Factor Theory:** 1. Participants injected with adrenaline or placebo under the guise of testing a multivitamin. 2. Participants in waiting room with confederate displaying different behaviors (euphoric or angry). - Findings: 1. Those informed of adrenaline effects attributed emotions to the injection. 2. Those misinformed or uninformed interpreted physiological arousal based on the situation. 3. Demonstrated how physiological arousal is interpreted differently depending on situational factors. **Summary of Emotional Processing** - **Brain Regions Involved:** - **Limbic System:** Emotional processing. - **Frontal Lobes:** Emotion expression. - Complex interaction among various brain regions for emotional experiences. - **Limitations of Traditional Approach:** - Lack of consensus on the number of emotions. - Lack of specific physiology tied to each emotion. - Difficulty in localizing emotions in the brain. **Stress** - **Definition:** A challenge to a person\'s capacity to respond to inner or outer demands, also a reaction to the challenge. - **Physiological and Emotional Arousal:** Stressful experiences lead to physiological and emotional changes that affect cognitive and behavioral efforts to cope. - **Nervous and Endocrine Systems:** Understanding stress physiology requires consideration of both systems. **Division of PNS: Autonomic Nervous System (ANS)** - Regulates smooth muscles, cardiac muscle, and glands. - **Sympathetic Division:** Activated during \"fight or flight.\" - **Parasympathetic Division:** Supports energy conservation and restoration. **Role of Hypothalamus** - **Stress Response Activation:** - Activates two pathways: 1. **Anterior Pituitary Pathway:** Releases hormones that activate the adrenal cortex, releasing glucocorticoids like cortisol for long-term stress management. 2. **Sympathetic Nervous System Pathway:** Stimulates the adrenal medulla, releasing adrenaline and norepinephrine for immediate \"fight-or-flight\" response. **Neural vs. Endocrine Communication** - **Neural Communication:** - Rapid, directed communication via neurotransmitters. - Quick activation and deactivation. - **Endocrine Communication:** - Hormones released into the bloodstream, affecting target cells. - Slower process, dependent on blood flow, and can continue acting even after the initial signal is gone. **The Hypothalamic-Pituitary-Adrenal (HPA) Axis** - Manages stress through: - **Neural Response:** Immediate activation of the sympathetic nervous system and adrenaline release for quick action. - **Endocrine Response:** Release of corticotropin-releasing factor (CRF) from the hypothalamus to the anterior pituitary, triggering ACTH and cortisol production for long-term stress management. - **Response Timelines:** - **Adrenaline Response:** Rapid, geared for quick action. - **Cortisol Effects:** Slower, maintaining stability and managing stress effects. - **Chronic Activation:** - Ongoing stress can become maladaptive; prolonged cortisol elevation can suppress the immune system, leading to health issues. - Importance of balancing acute stress responses with relaxation to avoid long-term negative effects. **Language and Aphasia** - **Definition of Aphasia**: A broad term for language disorders; from Greek \"a-phatos,\" meaning \'not speakable.\' - **Prefixes**: - **a-**: Without - **dys-**: Impairments **Basic Elements of Language** - **Phonemes**: The smallest sound units that change meaning (e.g., \"cat\" vs. \"bat\"). - **Morphemes**: The smallest units of language carrying meaning (e.g., \"un-\" in \"undo\"). - **Semantics**: The study of meaning in language. - **Syntax**: The arrangement of words to form sentences. - **Grammar**: The set of rules governing language use. **Signs of Aphasia** - **Paraphasia**: Substituting incorrect words or sounds. - **Neologism**: Creating entirely novel words. - **Non-fluent speech**: Speaking with considerable effort. **Related Impairments** - **Agraphia/Dysgraphia**: Inability/impairment to write. - **Alexia/Dyslexia**: Inability to read/impairment. **Classic Aphasiology Approaches** - **Paul Broca (1861)**: - Studied patients with impaired language functions. - Identified **Broca's Area** in the left inferior frontal gyrus, critical for speech production. - Damage results in **Broca's aphasia** (non-fluent speech, intact comprehension). - **Carl Wernicke (1874)**: - Discovered **Wernicke's Area** in the left superior temporal gyrus, responsible for language comprehension. - Damage leads to **Wernicke's aphasia** (fluent but meaningless speech, impaired comprehension). **Lichtheim\'s House Model (1885)** - Different brain areas for language processing; disconnections lead to various aphasia types: - **A**: Auditory Area (Wernicke\'s - comprehension). - **M**: Motor Area (Broca\'s - production). - **B**: Concept Area (higher-level processing). - Damage can impair comprehension, production, or repetition. **Wernicke-Geschwind Model (1972)** - Describes language processing as a step-by-step process involving: - Hearing and decoding words (auditory cortex to Wernicke\'s). 1. Signals sent to the **primary auditory cortex (temporal lobe).** 2. Comprehension processed in Wernicke\'s Area. 3. Information sent through the arcuate fasciculus to Broca\'s area for motor planning. 4. Response generated in the primary motor cortex. - Speaking a word (Wernicke\'s to Broca\'s). 1. Information sent to the **primary visual cortex (occipital lobe).** 2. Translated in the **Angular gyrus** (phonological and semantic codes). 3. Comprehension processed in Wernicke\'s Area. 4. Information sent through the arcuate fasciculus to Broca\'s area for motor planning. 5. Response generated in the primary motor cortex.  **Types of Aphasia** - **Broca\'s Aphasia** (Expressive Aphasia): - Damage to Broca's Area leads to **slow, effortful speech.** - Key symptoms: - **Impaired Speech** - Telegraphic speech (simple grammar/short sentences). - Difficulty retrieving words (anomia). - **Preserved comprehension, except for complex grammar.** - **Wernicke's Aphasia** (Receptive Aphasia): - Damage to Wernicke's Area results in **fluent but nonsensical speech.** - Key symptoms: - **Impaired comprehension.** - Use of semantic paraphasia's and neologisms. - Lack of awareness of their communication issues. - **Conduction Aphasia**: - Normal comprehension and production but **difficulty repeating non-meaningful words.** - Results from **damage to the arcuate fasciculus.** **Treatment** - **Speech and Language Therapy**: Aimed at improving communication abilities. Some may communicate through singing, which engages different brain areas. **High Order Cognition: Executive Functions and Key Brain Regions** **Executive Functions** Executive functions are cognitive processes that allow individuals to: - **Override automatic behaviors** (inhibitory control) for novel situations. - **Switch flexibly** between tasks (cognitive flexibility). - **Maintain goals** in mind while executing other tasks (working memory). Executive functions can be categorized into **Cold** and **Hot Executive Functions**: - **Cold Executive Functions**: - Deal with logical, abstract, unemotional tasks. - Involve reasoning, problem-solving, planning, and decision-making in non-emotional contexts. - Skills include working memory, cognitive flexibility, and inhibitory control. - **Key Brain Region**: Dorsolateral Prefrontal Cortex. - **Examples**: Solving math problems, organizing schedules, planning projects. - **Hot Executive Functions**: - Engage in emotionally charged or socially significant tasks where emotions and motivation play a role. - Govern impulse control, emotional regulation, and decision-making in emotional/high-stakes settings. - **Key Brain Regions**: Ventromedial Prefrontal Cortex, Orbitofrontal Cortex. - **Examples**: Resisting tempting food, managing conflict frustration, delaying gratification. Deficits in either type can lead to challenges in **emotional regulation** or **problem-solving**. **Important Regions of the Frontal Lobes** 1. **Primary Motor Cortex** 2. **Non-primary Motor Cortex** (Premotor Cortex, Supplementary Motor Area) 3. **Prefrontal Cortex** (PFC) -- further divided into key regions related to executive function: **The Prefrontal Cortex (PFC)** The PFC has multiple subdivisions: 1. **Dorsolateral Prefrontal Cortex (DLPFC)** - Known as the "executive circuit." - **Functions**: Working memory, planning, task-setting, problem-solving, sequencing, sustained attention, inhibition, cognitive flexibility. - **Deficits Following Damage**: - Poor working memory, planning, and task-setting. - Perseveration ("getting stuck"), poor inhibition, and cognitive inflexibility. - **Neuropsychological Measures**: - **F-A-S Test**: Measures fluency, potential perseveration. - **Digit Span Backwards**: Tests working memory. - **Tower of Hanoi/Tower of London**: Assesses task-setting, planning. - **Stroop Test**: Assesses inhibition. - **Wisconsin Card Sorting Test**: Tests cognitive flexibility. 2. **Orbitofrontal Cortex (OFC)** - Manages **emotional and social responses** and processes emotional stimuli. - **Deficits Following Damage**: - Emotional instability, social inappropriateness, diminished empathy, poor sensitivity to future outcomes. - **Neuropsychological Measures**: - **Family/Caregiver Reports**: Observations on social behavior, empathy. - **F-A-S Test**: Can reveal socially inappropriate responses. - **Bechara's Gambling Task**: Tests decision-making with changing rewards. 3. **Mediofrontal Cortex (MFC)** - Involved in **response monitoring**, **error detection**, and **motivational control**. - **Deficits Following Damage**: - Apathy, reduced verbal output, diminished emotional response (flat affect). - **Neuropsychological Measures**: - **Family/Caregiver Reports**: Observations on apathy. - **Motivation Scales**: Measures diminished drive. - **Reaction Time Tests**: Slower response times indicate MFC issues. **Acquired Brain Injury (ABI)** **Definition:** - Injury to the brain after birth, resulting in cognitive, physical, or behavioral deterioration. - Retains intellectual abilities. - Difficulty controlling, coordinating, and communicating thoughts and actions. - Considered an **invisible disability** with no obvious physical signs. - Symptoms may include fatigue, lack of initiation, anger, mood swings, and egocentricity, leading to unrecognized significant impacts. - Approximately two-thirds of individuals with severe brain injury experience good recovery but may face ongoing cognitive or behavioral challenges. **External Causes:** - **Traumatic Brain Injury (TBI):** - Results from accidents, falls, assaults, sports injuries, or work-related incidents. - **Other Causes:** - Poisoning, infections (e.g., meningitis, encephalitis), diseases (e.g., HIV/AIDS). - Alcohol and drug abuse. **Internal Causes:** - Conditions such as strokes, cerebrovascular accidents, tumors, oxygen deprivation, and secondary effects of TBI (e.g., swelling, epilepsy). - Progressive conditions like Alzheimer's, Parkinson's, and Multiple Sclerosis. **Traumatic Brain Injury (TBI)** **Pathomechanism:** - Injury typically involves shearing, stretching, and tearing at the neuron level. **Types:** 1. **Penetrating Head Injury:** - Involves an open wound. 2. **Closed Head Injury:** - No penetration, but brain damage occurs due to marked acceleration or deceleration. - The brain may collide with the skull, leading to bruising, swelling, or tearing. **Subtypes:** - **Contusions:** - Bruising of the brain from impact. - Can damage blood vessels, causing internal bleeding and haematomas (clotted blood masses). - **Concussion:** - Temporary disturbance of brain function (e.g., loss of consciousness, confusion). - No visible structural damage like bleeding. - Repeated concussions can lead to **Chronic Traumatic Encephalopathy (CTE)**, a progressive brain disease. **Consequences of TBI:** - **Physical:** - Fatigue, headaches, paralysis, chronic pain, dizziness. - **Emotional/Behavioral:** - Lack of motivation, depression, social issues, emotional lability, irritability. - **Cognitive:** - Memory problems, poor concentration, impulsivity, poor problem-solving, inflexibility. **Strokes** 1. **Ischaemic Stroke:** - **Cause:** Blood clot blocks blood flow to the brain. - **Mechanism:** - Thrombus forms at the blockage site. - Embolism: A clot travels from elsewhere in the body to block a brain artery. - Atheroma (fatty deposits) in arteries narrows passageways, leading to clots. 2. **Haemorrhagic Stroke:** - **Cause:** Rupture of an artery in the brain, causing blood leakage. - **Mechanism:** - Rupture may result from conditions like aneurysms. - Leaking blood damages brain cells and deprives the affected area of oxygen and nutrients. **Severity Classification** 1. **Glasgow Coma Scale (GCS):** - A scale to assess consciousness level post-injury (scores range from 3 to 15). 2. **Loss of Consciousness (LOC):** - Duration of unconsciousness following injury. 3. **Post-Traumatic Amnesia (PTA):** - Duration of memory loss/confusion post-injury. **Categories:** - **Mild Brain Injury:** - GCS: 13-15 - LOC: Less than 30 minutes - PTA: Less than 24 hours - **Moderate Brain Injury:** - GCS: 9-12 - LOC: 30 minutes to 24 hours - PTA: 1-7 days (confusion, memory issues). - **Severe Brain Injury:** - GCS: 3-8 - LOC: More than 24 hours - PTA: More than 7 days (significant confusion, memory problems). **Role of Clinical Neuropsychologists** - Assessing persistent symptoms and their functional impact. - Educating families and developing strategies to compensate for cognitive deficits.