Psych 345 Study Guide 2024.pdf

Psychology 345: Human Neuropsychology – Fall 2024 Study Guide I* Background What is neuropsychology and why is it important? - Study of the relationship between brain and behavior (both clinic and research field) - Many major discove...

Psychology 345: Human Neuropsychology – Fall 2024 Study Guide I* Background What is neuropsychology and why is it important? - Study of the relationship between brain and behavior (both clinic and research field) - Many major discoveries and insights have come from individual clinical cases - Brain damage reveals what are otherwise invisible components of the mind - You often learn about how something works when there is something wrong with it Advantages and disadvantages of studying patients with lesions - Advantages: - Able to identify the location and extent of a brain injury - Group of patients: identify location commonly lesioned among patients showing same disorder or lack of function - Disadvantages: - Lesions often diffuse and not confined to a single area - Some areas may be more plastic than others - Sometimes hard to make straightforward inferences between brain and behavior Phrenology – basic tenets, founders of, opposition to - Study of the structure of the skull to determine a person’s character and mental capacity - Implications of Broca and Wernicke findings: - Shift away from phrenology toward physiologically real function - Motor: expressive language - Sensory: receptive language - Front-back division: - Broca’s motor aphasia - Wenicke’s sensory aphasia - Original traits: - Cleverness - Secretiveness - Memory for people - Memory of things & facts - Sense of color, pictorial talent - Love of god & religion - Founded by: Joseph Gall, Spurzheim (early 1800s) - Opposition to: - Paul Broca (localization and lateralization; 1860s) - Patient Tan - Production of language localized to left frontal operculum region of the brain - Broca’s area - Carl Wernicke (localization and lateralization; 1874) - Followed up on Broca’s research - Comprehension of language localized to a more posterior portion of the brain- left temporal lobe - Wernicke’s area Theoretical advances of Hughlings Jackson and Alexander Luria - Hughlings Jackson  - Ideas mixed localization and holistic views - Brain organized into a hierarchy - Spinal cord & cerebellum - Motor region (including basal ganglia) - Prefrontal cortex & sensory cortex - Negative symptoms: refer to the loss of function due to brain damage - Positive symptoms: abnormal activities that emerge when brain function becomes disorganized - Alexander Luria - Functional systems model of the cortex - Hierarchy within each “unit” (posterior & anterior) - Different brain areas have specialized roles but are not sufficient on their own to produce a function - Current Views - Functions consist of multiple processes that occur in specific areas of the brain - Imaging studies reveal the different processes that occur both serially and in parallel - Even simple mental activity requires coordination of processes in multiple areas of the brain Laterality, hierarchical organization of brain - Left, right organization - Functional hierarchy - “older” and “newer” brain structures - Left Hemisphere: - Often associated with language, logic, analytical thinking, and mathematical skills. - It controls the right side of the body (because of contralateral organization, where each hemisphere controls the opposite side). - In most people, particularly right-handed individuals, language processing (e.g., Broca’s area and Wernicke’s area) is localized in the left hemisphere. - Right Hemisphere: - Typically linked to spatial abilities, creativity, emotional processing, intuition, and visual-motor tasks. - It controls the left side of the body. - The right hemisphere is more involved in recognizing faces, interpreting emotional expressions, and processing nonverbal information. localization of function vs. anti-localizationism/holism - Localization: Different brain areas have different functions that work together - Even simple mental activity needs coordination of multiple brain areas - Anti-localization: the whole brain is involved in most cognitive processes, meaning no single area is solely responsible for a specific function Neuroanatomy/ brain structure (know how to recognize and locate structures in relation to one another) Forebrain, midbrain, hindbrain, brainstem, and major parts of each, and their functions 3 Main Brain Divisions: 1. Forebrain: higher cognitive functions (voluntary movement, reasoning, language) a. Cerebrum: initiates and coordinates movement and regulates temperature b. Thalamus: relay station for sensory and motor info, all sensory modalities make connections in thalamus (except olfaction) → then go to primary sensory areas in cortex c. Hypothalamus: Maintains balance of homeostasis 1. Midbrain: Motor movement and sensory processing 2. Hindbrain: automatic functions such as respiratory rhythms and sleep a. Pons: vital body movements, relays signals from cerebellum to forebrain b. Medulla oblongata: Involuntary functions: breathing, heart rate, blood pressure c. Cerebellum: motor coordination, motor learning Brainstem - Begins where the spinal cord enters the skull, and extends to lower areas of forebrain - Three main regions: - Hindbrain, midbrain, diencephalon Four lobes: frontal, parietal, temporal, occipital; and their boundaries (landmarks); major gyri and fissures/sulci 1. Frontal: voluntary motor control 2. Parietal: somatosensory 3. Temporal: auditory 4. Occipital: visual - Major landmarks: - longitudinal fissure separates left and right hemispheres - Central sulcus/fissure separates parietal and frontal lobes - Lateral (sylvian) sulcus/fissure dorsal boundary of temporal lobe Midbrain (a.k.a. tectum): superior colliculus (eye movement control), inferior colliculus (auditory localization) - Superior colliculus: receives projections from retina to control eye movements - Inferior colliculus: receives projections from the ear to control eye movements - Both help locate objects/events in space Meninges: dura mater, arachnoid membrane, pia mater - Meninges: the three layers of membranes that protect the brain and spinal cord 1. Dura Mater: tough, hard outer layer 2. Arachnoid membrane: web-like structure filled with fluid that cushions the brain 3. Pia Mater: delicate inner layer that clings to the surface of the brain Cerebral spinal fluid, ventricles (lateral, third, cerebral aqueduct, fourth) - Ventricular system is filled with 4 ventricles, all of which are filled with cerebrospinal fluid 1. Lateral Ventricle (left and right) 2. Third Ventricle 3. Cerebral Aqueduct 4. Fourth Ventricle Neurons, glia (types); gray matter, white matter, functions of neurons versus glia - Function of Neuron: Communicating units of the Central Nervous System - Receive stimulation from dendrites; integrate input from other neurons - Transmit signals via axons; release neurotransmitters - Synaptic connections with other neurons - Function of Glia: Support, insulate, and nourish - Non-neuronal cells in CNS and PNS - Do not generate action potentials - Hold neurons in place, supply nutrients and oxygen, insulate neurons, destroy pathogens & remove dead neurons - Gray Matter: neuronal cell bodies (glia too); forms nuclei and cortex - White Matter: axons, myelin (glia too) Primary cortex (its characteristics), secondary cortex, association cortex; - Primary Cortex: Initial recipient of sensory information or the direct controller of motor movements - Receive sensory info from sensory organs to process simple, direct info with MINIMAL  integration - Secondary Cortex: Integrates info from primary areas and the thalamus to refine the primary area’s stimuli - Processes more complex aspects of stimuli (recognizing objects) - Association Cortex: Integrates, processes, and analyzes stimuli, and is involved in higher mental functions Varieties of white matter tracts, corpus callosum, intra- vs. inter-hemispheric connections - White matter tracts: large collection of axons traveling toward or away from a nucleus/layer in the CNS - bundles of myelinated axons that connect different regions of the brain and spinal cord. These tracts are essential for communication between neurons, facilitating the transfer of information within the brain and between the brain and the rest of the body - Can be short/long, intra-hemispheric, or interhemispheric - U fiber (short, same hemisphere), fasciculi (long, same hemisphere), corpus callosum (in between hemispheres) - Intrahemispheric (within) and Interhemispheric (between) Cytoarchitecture of cerebral cortex: six layers, characteristics of input and output layers, different organization in different cortical areas - Two major types of brain maps for classifying and defining cortical regions 1. Cytoarchitectonic Map: Regions are defined by their organization, structure, and distribution of cortical cells - Cortical Laminae (Layers of the Cortex) - Six layers of cell bodies (gray matter), 2-3 mm thick, layers differ in connections, thickness, cellular composition - Below is white matter (myelinated axons) 1. Layer 1 a. Few cell bodies, axons/dendrites from elsewhere in the brain 2. Layer 2, 3, 5, & 6 a. All referred to as sending layers: they send axons to other layers 3. Layer 2: a. Association layer b. Intrahemispheric (within) 4. Layer 3: a. Association layer and commissures b. Intrahemispheric (within) and Interhemispheric (between) i. Not only communicates within the hemisphere, but also sends fibers to the opposite hemisphere 5. Layer 4: a. Major receiving layer b. Gets sensory fibers from the sensory and association cortex c. Input from thalamus d. Thicker in sensory cortex 6. Layer 5: a. Sends information to the brainstem and spinal cord b. Cortico-spinal (cortex-spine)- gets information out of the cortex to go elsewhere 7. Layer 6: a. Sends information to the thalamus (bunch of different types of cells, called polyform) b. Cortico-thalamic 2. Topographic Map: regions are defined by various inputs and outputs of the cortex - Also known as projection maps  - Defined by their afferent input (kind of signals they get from the periphery) and efferent output (kind of signals that they send) - What gets mapped depends on the sensory modality - Vision: visual field - Audition: pitch - Touch: body surface Properties of Cortical Organization - Hierarchical Organization - From modality-specific regions (one sense) to increasing integration (many senses) - Association within a modality: intramodal - Association across modalities: intermodal (takes place association cortex) - Contralateral Organization: - Left hemisphere represents: - Right side of the body - Right ear input - Right visual field - Vice versa for right hemisphere - Via decussation - crossing of the midline Specific Studies/Scientists to know Broca’s and Wernicke’s cases and their importance - Broca’s Area - Ability to comprehend language, but difficulty speaking or forming words - Wernicke’s Area - Inability to comprehend language, but could speak words fluently that made little sense - Implications of Broca and Wenicke’s findings - Shift away from phrenology toward physiologically real functions - Broca’s area responsible for motor expressive language - Wernicke’s area responsible for sensory aspects of language, receptive language - Front Back division - Damage to frontal regions (broca’s area) likely to cause broca’s motor aphasia - Damage to posterior regions (wernicke’s) likely to cause wernicke’s sensory aphasia Brodmann – cytoarchitectonic map - System for classifying different regions of the brain based on their cellular structure and organization - Identified 52 different regions based on cell layers - Structural classification = functional differences - Widely used to refer to human brain areas Penfield –electrical stimulation studies, sensory and motor homunculi - Neurosurgeon who mapped somatosensory & motor maps using electrodes - He stimulated specific areas of patients’ brains while they were awake during surgery, and asked patients to describe sensations when different brain regions were stimulated, allowing Penfield to map the brain - Homunculus (sensory & motor) - The maps are orderly: adjacent on the body, adjacent on the cortex (mostly) - More sensitive regions on the body surface get more cortical representation – this is called cortical magnification - Body parts with more sensory sensitivity get more cortical representation Ramachandran – phantom limb phenomenon, cortical reorganization - Many amputee patients still have the sensation that their missing limb is still attached - Some patients may feel pain in the missing limb - For many patients, phantom limb phenomenon goes away from 2-3 years - Ramachandran showed that an amputated limb still has representation in the somatosensory cortex  - However, not all patients experience the same phantom limb sensations - Sensation in the missing limb could be produced by touching a body part that has been appropriated the missing limb’s old “acreage” in the cortex - Cortical Reorganization Theory - Sensory input is missing for hand area due to amputation - Cells in adjacent cortical face area “take over” hand area - Physical sensation on face now activates cortical “hand” area Holmes- retinotopic map in primary visual cortex - Holmes discovered that the primary visual cortex (V1) is organized in a way that reflects the spatial layout of the retina - Means that different parts of the retina are represented in specific areas of V1 - Creates a retinotopic map, where neighboring areas on the retina correspond to neighboring areas in V1 - The central part of the visual field (where vision is sharpest) occupies a disproportionately large area in V1 compared to the peripheral parts - Equi-visibility: Objects in the periphery must be physically LARGER to be as visible as objects falling on the fovea - Damage to specific parts of the occipital lobe result in predictable blind spots depending on which part of V1 was affected Poppel, Held & Frost – saccadic localization study of blindsight - Explains how individuals with damage to their primary visual cortex (V1) could still respond to visual stimuli without conscious awareness, known as blindsight - Blindsight occurs when patients with lesions in the V1 lose conscious visual perception in part of their visual field (scotoma), but are still able to respond to stimuli in that blind area without being aware of it - Researchers found that, even though patients claimed they could not see anything in their blind area, they could still make accurate saccades (quick eye movements) toward visual stimuli presented in that blind field - Demonstrates that patients’ brains could unconsciously localize visual stimuli and respond to them without involving the visual areas responsible for conscious vision - Provided evidence that the brain has multiple pathways for processing visual information, some of which operate below the level of conscious perception - Blindsight theories: 1. Non-striate hypothesis: a. Retino-tectal pathway- direct route for saccadic eye movement (retina → superior colliculus) b. Tecto-pulvinar extrastriate pathway: Indirect route (bypasses striate cortex) for behavioral responses c. Recap: An alternative visual pathway is responsible for “residual” vision 2. The cortical islands (striate) hypothesis a. Detailed (micro) perimetry i. Microperimetry: assess the visual function of a very specific area of the retina b. Revealed islands of vision in scotoma c. Implications: spared tissue in Area 17 can explain residual vision d. Recap: Spared islands of primary visual cortex are responsible for “residual” vision Fendrich – micro-perimetry, cortical islands hypothesis of blindsight 3. The cortical islands (striate) hypothesis a. Detailed (micro) perimetry i. Microperimetry: assess the visual function of a very specific area of the retina b. Revealed islands of vision in scotoma c. Implications: spared tissue in Area 17 can explain residual vision d. Recap: Spared islands of primary visual cortex are responsible for “residual” vision Ungerleider & Mishkin-- what & where pathways - What Pathway (Ventral Stream): - Involved in object recognition and identifying what something is  - Runs from the V1 (primary visual cortex) to the ventral stream TEMPORAL LOBE - Responsible for processing attributes like color, shape, and texture, allowing us to recognize and identify objects - Where Pathway (Dorsal Stream) - Associated with spatial awareness and locating objects in space - Runs from the V1 to the dorsal stream PARIETAL LOBE - Responsible for determining the position of objects and guiding movements in relation to these objects, such as reaching or grasping Cognitive Neuroscience Methods Converging methods/operations - Definition: an approach to answering a question through interrelated set of experiments to see if the same conclusion is reached - Diff methods of subject populations are used (animal experimentation, lesion studies, brain imaging) - Improves researchers’ ability to understand relationship between brain events and cognitive processes - Populations of subjects: patients with brain damage, neurologically intact individuals, animals Neuroimaging (structural vs. functional): CT, MRI, DTI (white matter tractography); fMRI, EEG/ERP, PET, TMS; safety issues, temporal and spatial resolution, what is detected - Structural Imaging Methods a. Visualize anatomical structures of the brain b. Can do a live person or a cadaver (dead person) c. Static in time d. Computer (Axial) Tomography (CAT or CT), Magnetic Resonance Imaging (MRI), Diffusion Tensor Imaging (DTI) - Functional Imaging Methods (not an exhaustive list): e. Visualizes active processes in the brain f. Can do ONLY on a live patient g. Dynamic in Time h. Positron Emission Tomography (PET), Functional Magnetic Resonance Imaging (fMRI), Electroencephalography (EEG), Event-Related Potentials (ERP) - Spatial Resolution - The amount of detail you can see in the image - Relevant for both structural and functional imaging - Structural imaging: amount of neuroanatomical detail you can see - Functional imaging: precision with which you can localize activation to specific brain regions - Analogy: resolution of digital camera: how grainy are your pictures - Temporal Resolution - The precision with which you can localize brain activation to a specific point in time - ONLY relevant in functional imaging - Poor temporal resolution- the activity in visual cortex occurred sometime within the 10 minutes after the visual stimulus was presented - Good temporal resolution- the activity in visual cortex occurred sometime within the 250 milliseconds after the visual stimulus was presented 1. CT (Computed Tomography) i. Tomography is imaging by sections j. Maps density  i. Basically an “x-ray absorption map” k. Different tissues absorb different amounts of x-ray radiation → look different on the image l. Poor spatial resolution compared with an MRI m. Not performed anymore due to safety issues (large exposure to radiation) 2. MRI (Magnetic Resonance Imaging) a. Basically a “proton density map” b. Different tissues have different proton densities (and magnetic properties) and look different on the map c. Most protons in biological tissues are in the form of H2O and different types of tissue have different concentrations of water d. Good spatial resolution compared to CT e. Proton map creased by measuring electrical current produced by aligned protons in brain tissue f. MRI Scanner is basically a very strong magnet, cannot be used for patients with metal implants or certain devices 3. DTI (Diffusion Tensor Imaging) a. Uses the diffusion of water molecules to analyze white matter structure b. Spatial resolution moderate to high c. Safety issues similar to concerns of standard MRI 4. fMRI a. Basically a “blood oxygenation level map” b. BOLD technique: Blood Oxygenation Level Dependent i. More oxygenated blood in regions of increased neural activity, crating a brighter region ii. Oxygenated blood has different magnetic properties than de-oxygenated blood due to hemoglobin c. Brain regions with different levels of oxygen in the blood have different magnetic properties, appear different on MRI images d. The more oxygen in the blood in a region, the brighter this region will look in an output image (statistical map) of an fMRI scan e. Colored areas = functional image f. Colors are added by the data analyzer ☺ g. Functional data overlaid on a structural MRI (black & white) h. Can be used to measure brain activity associated with doing a specific task i. Relative measure: always a comparison j. Resting state fMRI can measure brain activity when a subject is not performing an explicit task Best spatial resolution of all functional techniques (compared to PET) k. Good temporal resolution (compared to PET) l. Same safety issues as an MRI, uses the same equipment m. Temporal resolution: Takes only seconds to take a snapshot, has much better temporal resolution than PET 5. EEG/ERP a. EEG: i. The electrical activity of neurons produces changes in electrical fields ii. EEG records these changes (potentials) via electrodes placed on the scalp iii. Provides a continuous recording of overall brain activity iv. Predictable EEG signatures are associated with different behavioral states v. Normal EEG patterns are well established vi. EEG recordings can be used to detect abnormalities in brain functionEEG & Epilepsy vii. Strip/grid or depth electrodes placed under the scalp viii. Video EEG over several days to observe symptoms and map origin of seizure ix. Remember, good temporal resolution!  x. Helps determine whether person is a good candidate for surgery b. ERP: i. Measures neural activity related to a particular event ii. Event can be a sensory stimulus, movement, etc. iii. Electrical potentials across the scalp are measured as in EEG (same equipment) iv. A time-locked period of neural activity, measured after each of many repetitions of an event, is averaged v. Example Experiment: 1. Present a subject with a series of repetitive tones 2. Occasionally, play an “unexpected” tone (one that differs from the other tones in some way) 3. Record from scalp electrodes while you’re doing this and you’ll get data that look like this... vi. ERP/EEG is good for figuring out the time course of cognitive events vii. Best temporal resolution viii. fMRI (and PET) are good for understanding where in the brain these cognitive events occur 1. Best spatial resolution 6. PET (Positron Emission Tomography) a. Basically a “blood flow” map b. Areas with more active neurons receive more oxygenated blood c. Worst temporal resolution of functional techniques (compared to fMRI and to EEG/ERP) d. Can be used to measure resting brain activity e. Can be used to measure brain activity associated with doing a specific task f. Requires a subtraction process g. PET does not directly measure neuronal activity but is inferring activity based on assumption that blood flow increases where neuron activity increases h. Areas with more blood flow (areas of the brain that are more active) emit more radioactivity i. Safety Issues: exposure to radiation, invasive (radioactive substance injected into the body) j. Poor spatial resolution compared to fMRI 7. TMS (Transcranial Magnetic Stimulation) a. Pulses of electromagnetic field from coil induce an electric field in the brain b. Can either excite the cortex (e.g. induce movement) or disturb its function c. Cortical surface, not deep structures d. In the "lesion" mode TMS can temporarily suppress perception or interfere with task performance e. Confirm findings from lesion method that implicate brain regions as playing role in mental function f. Repetitive TMS (rTMS): Potential therapeutic use over left frontal regions alleviates symptoms of depression g. Last resort; must have multiple treatment failures h. Safety Issues: Potential to induce a seizure, even in subjects without any predisposing illness Which one of these methods: 1. Is not a visualization method? TMS 2. Has the best temporal resolution? EEG/ERP 3. Is the most invasive? PET 4. Which modulates brain activity? TMS 5. Has the worst spatial resolution? EEG/ERP 6. Has the best spatial resolution? MRI 7. Is used for functional imaging? fMRI & PET 8. Measures X-ray absorption? CT Patient studies: Single-case/group/multiple-case studies (advantages/disadvantages of each) 1. Single case studies focus on a single individual, typically with a unique neurological condition or injury a. Advantages: i. Provides in-depth insights into the specific cognitive or behavioral deficits associated with the individual’s condition ii. Allows for detailed longitudinal observations over time iii. Useful for rare conditions where large samples not feasible b. Disadvantages: i. Limited generalizability to the broader population ii. Potential for subjective interpretation of results iii. Risk of overemphasizing unique findings without context 2. Group Studies involve a larger group of individuals with a similar condition, allowing for comparison against a control group a. Advantages: i. Greater statistical power to generalize findings to a wider population ii. Can identify common patterns of impairment amcross individuals b. Disadvantages i. May overlook individual differences and nuances in cognitive profiles ii. Variability within the group can obscure findings 3. Multiple-Case Studies examine several individuals with a similar condition, often with a focus on comparing and contrasting their profiles a. Advantages: i. Balances individual depth with the broader applicability of group studies ii. Helps identify patterns in cognitive function b. Disadvantages: i. Can be complex to analyze and interpret due to variability ii. May require more resources and time than single-case studies Premorbid abilities and how they are assessed - Definition: an individual’s cognitive and functional skills before the onset of a neurological condition or injury. Assessing these can be crucial for understanding the impact of the condition 1. Referral a. comes from health professional b. specify the aim of the assessment c. provide an up-to-date picture of patient’s impairments and deficits 2. Clinical interview a. enables neuropsychologist to form a picture of the patient’s difficulties 3. Assessment procedures and context a. perform various tests that takes 3+ hours (multiple sessions) b. only test if the person feels well there can be a number of different reasons for obtaining a poor score on any subtest 4. Neuropsychological assessment report a. neuropsychologist writes a report for the referral agency Neuropsychological tests: Approaches: test-battery vs. customized assessment 1. Test-Battery Approach a. Definition: Involves the administration of a standardized set of neuropsychological tests designed to evaluate a range of cognitive functions b. Definition: Administers a standardized set of tests covering various cognitive domains. c. Advantages: i. Comprehensive overview of cognitive functions. ii. Results can be benchmarked against normative data.  d. Disadvantages: i. Less individualized; may overlook unique cognitive profiles. ii. Potential redundancy in assessing similar abilities. 2. Customized Assessment a. Definition: Tailors test selection to the individual’s specific history and concerns. b. Advantages: i. Provides tailored insights into specific cognitive deficits. ii. Allows flexibility and targeted evaluations. c. Disadvantages: i. Lacks standardization, complicating comparisons. ii. More time-consuming to develop and administer. Specific tests and what they measure: WAIS, Hooper, Rey- Osterrieth Complex Figures, Halstead-Reitan Battery, WCST, National Adult Reading Test, Stroop, Trail making Test 1. WAIS (The Wechler “family” of intelligence tests; Wechsler Adult Intelligence Scale) a. Composed of verbal and performance subtests to provide a profile of abilities b. Provides three overall scores: Verbal IQ, Performance IQ, and Full Scale IQ c. Some subtests of the WAIS-III measure visuospatial/perceptual abilities i. Rey-Osterrieth Complex Figure test (spaceship): 1. “I’ll show you an image, then I’ll ask you to recreate that image: 2. Measures: Visual perception, visual attention, motor control, executive control (planning, strategy), memory 2. Hooper Visual Organization Test a. Asses visual organization and cognitive ability to mentally manipulate fragmented images, often used to evaluate brain injury or neurological disorders b. Measures: visual perception, visual integration (parts into wholes) 3. Halstead-Reitan Battery a. Comprehensive set of tests designed to assess brain function and identify cognitive impairments resulting from neurological damage 4. Wisconsin Card Sorting Test (WCST) a. Subjects sort cards according to rules based on different visual dimensions (color, shape, number) that change without warning. Participants must figure out the sorting through trial and error and adapt when the rule changes b. Measures: Attention, Strategy switching (cognitive flexibility), Planning, Memory, Inhibition (of old sorting rules), People with Frontal Lobe Disorder don’t understand that they need to sort into particular strategy, some cannot learn from errors, some stick to older strategy (perseveration) 5. National Adult Reading Test a. Participants asked to read aloud 50 irregularly spelled words (yacht, colonel) that do not follow typical phonetic rules, so reading them correctly requires prior knowledge rather than phonetic decoding b. Measures long term memory, verbal ability 6. Stroop Task a. Participants are shown words that are color names , but the words are printed in colors different from the word itself. They’re asked to name the color of the ink, not the word itself b. Measures: Inhibition (the ability to inhibit a prepotent response (reading) 7. Trail-Making-Test a. Two part test, asking patients to first connect numbered circles from 1 - 25 in sequential order as quickly as possible, and then to alternate between connecting numbers and letters in a sequence (1, A, 2, B) as quickly as possible b. Measures: motor control: Visual attention, Visual search, Executive control abilities, Sequencing, Planning, Goal maintenance, Strategy switching/ changing mental set, Inhibition (1-2-3 more automatic than 1-A-2-B) Single and double dissociations - Single dissociation: Occurs when damage to one brain area affects one cognitive function but not another - Ex: Broca’s aphasia- ability to understand speech, but can no longer speak - Double dissociation: Involves two patients with opposite deficits, showing two cognitive functions are independent of each other - Ex: What and where pathways, broca’s and wernicke’s aphasia Criteria radiologists use for diagnosing dysfunction - ??? Orientational Terminology Anterior/posterior (rostral/caudal); dorsal/ventral (superior/inferior); lateral/medial Unilateral, bilateral. contralateral, ipsilateral, decussation, contralesional, ipsilesional, Lateral relations: - Contralateral (opposite sides) - Ipsilateral (same side) - Unilateral (one side) - Bilateral (both sides) Decussation: - Crossing of fibers from one side to the other - From left body to right brain (or vice versa) - From right body to left brain Contralesional: - Definition: Refers to the side of the side of the body or brain that is opposite to the location of a lesion - Ex: If a stroke occurs in the right hemisphere of the brain, the effects may be seen on the left side of the body Ipsilesional: - Definition: Refers to the side of the body or brain that is the same as the location of a lesion - If the right hemisphere is damaged, any effects observed on the right side of the body as considered ipsilesional (difficulty movement/sensation) Planes of section: horizontal, coronal, (mid versus para) sagittal, transaxial Cortical Maps Contributions of Golgi and Cajal - Golgi: - Reticular Theory: Proposed that the nervous system is a continuous network of interconnected neurons. - Golgi Stain: Developed a staining technique that highlighted individual neurons, allowing for the detailed observation of their structure. - Cajal: - Neuronal Doctrine: Argued against Golgi’s theory, stating that neurons are separate entities that communicate at synapses. - Neuronal Maps: Created detailed drawings of various neuron types and their connections, emphasizing the complexity of the nervous system. - Plasticity: Contributed to understanding how neural connections can change with experience. Cytoarchitectonic maps (Brodmann’s map) - Brodmann’s Map - Identified 52 different regions based on cell layers - Structural classification = functional differences - Widely used to refer to human brain areas Projection maps; retinotopic, tonotopic, somatotopic organizations Retinotopic Map: - Definition: Binocular visual field; mapping of visual input from the retina to the visual cortex. Adjacent areas in the retina correspond to adjacent areas in the visual cortex - Preserved what you see, or the image projected onto the retina, in order to transmit a complete map of the visual field Tonotopic: - Definition: Used for the auditory system, where different frequencies of sound are represented in specific areas of the auditory cortex - In the cochlea of the inner ear, high-frequency sounds activate hair cells at the base, while low-frequency sounds activate hair cells at the apex. This frequency organization is preserved in the auditory cortex, allowing for the discrimination of different pitches Somatotopic: - Definition: Mapping of body parts to specific areas in the somatosensory cortex and motor cortex. Each body part is represented in a way that corresponds to its physical size and importance in sensory perception/motor control - Areas of the body correspond to points in the primary somatosensory cortex (i.e. touch, pain, temperature)  - Homunculus is a visual representation of somatotopic organization, where the face and hands are represented by larger areas in the cortex due to their high sensitivity and motor control compared to other body parts Sensory homunculus, motor homunculus - The maps are orderly: adjacent on the body, adjacent on the cortex (mostly) - In sensory homunculus, more sensitive regions on the body surface get more cortical representation – this is called cortical magnification - In motor homunculus, body parts with more precise movement control (hands and face) get more cortical representation - BOTH homunculi are depicted as distorted figures, with body parts sized according to their representation in the brain rather than their actual physical size - For example, the hands, lips, face appear disproportionately large compared to legs Cortical magnification - The increase in the amount of cortical area dedicated to body parts that have high sensitivity Definition and function of receptive field - Definition: The region of the sensory surface that makes a cell fire - Touch: the location on the body - Vision: the locations on the retina (in the eye) - Audio: the regions of the basilar membrane (in the cochlea) - Function: Helps brain to process and localize sensory input, allowing the nervous system to detect and respond to stimuli from the environment - The size and complexity of receptive fields vary depending on the type of sensory input. In areas requiring fine discrimination (e.g., the fingertips or the fovea in the retina), receptive fields are smaller, allowing for more precise sensory perception. Generic sensory pathway: sensory receptors thalamus primary cortex secondary cortex association cortex - Thalamus: Sensory gateway; all sensory modalities make connections in thalamus (except olfaction) → then go to primary sensory areas in cortex - Sensory receptors (external stimuli like light, sound, or touch) → thalamus (acts as a relay station) → primary cortex (first cortical area to receive sensory input) → secondary cortex (further processes sensory input with more detailed analysis → association cortex (integrates sensory data with memory, cognition, etc) Brain Damage know the general meaning of: Focal vs. diffuse Area of damage: Focal - Specific, localized area of damage or dysfunction Diffuse  - Refers to a condition or damage that is spread over a larger, more generalized area Types of damage to brain cells: Lesion - Broad term, used to describe an abnormal area of brain tissue stemming from injury or disease Infarct - Dead brain tissue Ischemia - A condition in which blood flow is cut off or restricted from a particular area - The tissue becomes starved of oxygen and nutrients (glucose) - If deprivation lasts ~10 mins, cell death Subarachnoid Hemorrhage - Rupture of a cerebral artery (most arteries run along the surface of the brain in the subarachnoid space) - Can lead to ischemia (blood flow is cut off or restricted) - Can result in a subdural hematoma (a clot of blood on the surface of the brain) causes increased intracranial pressure - Blood can block drainage of CSF from the ventricles - causes increased intracranial pressure Hematoma - A clot of blood on the surface of the brain- causes increased intracranial pressure Cerebrovascular Causes: Thrombosis - clot IN the blood vessel that has coagulated and remains at point of formation; obstructs blood flow Embolism - Clot brought through blood from a larger vessel and forced into a smaller one Aneurysm - Vascular dilations (widening) resulting from local defects in blood vessel elasticity - Balloon-like expansions of vessels that are weak, prone to rupture - Rupture leads to subarachnoid hemorrhage, cerebral hematoma - Can be congenital (present at birth) - Can develop from hypertension, arteriosclerosis, infections Brain Tumors: Tumor - A mass of new tissue that persists and grows independently of its surrounding structures and has no physiological use - Most brain tumors grow from glia or other support cells rather than from neurons Encapsulated - A tumor that is a distinct entity in the brain Infiltrating tumors - A tumor that is not clearly marked off from surrounding tissue, may destroy or surround existing normal neurons and glia and interfere with their functioning Three major types of brain tumors: Glioma - Arise from glial cells - Can be benign or malignant - Lots of subtypes, based on type of originating glial cell Meningioma - Growths attached to the meninges - Entirely outside the brain (thus encapsulated)  - Usually benign Metastatic - A tumor established by a transfer of tumor cells from elsewhere in the body Head Injuries can cause: Edema - Collection of fluid around damaged tissue - Leads to swelling and increased intracranial pressure (more squishing) Open-Head Injuries - Brain injuries in which the skull is penetrated (e.g., gunshot) Closed-head injury - Resulting from a blow to the head (e.g., car accident, fall, impact sports - A blow subjects the brain to several mechanical forces due to movement of brain inside the skull (coup, contrecoup, shearing) Neurotoxicity - When the exposure to natural or man-made toxic substances alters the normal activity of the nervous system, disrupting or killing neurons and glia - Can result from exposure to: - Radiation therapy or chemotherapy - Heavy metals (e.g., lead or mercury) - Drugs (e.g., MPTP, alcohol) - Certain foods and food additives - Industrial and/or cleaning solvents (huffing) Alzheimer’s Disease - An example of a neurological disease, can cause widespread cortical degeneration Neuroplasticity What it is, and its levels and temporal scales; examples of synaptic and network level plasticity - Definition: The process of creating new neural pathways and modifying existing ones - Levels: - Cellular Level (Synaptic plasticity): Structural changes in dendritic and axonal anatomy - Changes in membrane excitability, pre and post synaptic properties (potentiation) - Changes communication between neurons - Network plasticity: Connectivity changes with disuse - Two weeks of “casting” associated with decreased “connectivity” with other brain regions - Connectivity = correlated activity - Homotopic = mirror area in opposite hemisphere - Ex: After brain injury, undamaged parts of brain take over functions that were previously managed by damaged areas - Temporal Scales - Short term: Changes occur within minutes to hours (e.g., synaptic changes during learning) - Immediate: cell death, edema, metabolic changes, inflammation (immune response) - Effects on structure and function of adjacent areas - Long term: Can take days, weeks, or even years (e.g., structural changes in neural networks after rehabilitation from injury) - Within days: axon sprouting, synaptic changes, network changes  (reestablishment of connections) Hebbian learning principle - From Donald Hebb (1949) - Consistent, coordinated activity between pre- and post- synaptic neurons strengthens their connections - In other words, neurons that fire together, wire together - Neurons with consistent uncoordinated/ uncorrelated activity: connection will weaken - In other words, neurons that fire apart, wire apart Phantom limb phenomenon, Cortical reorganization - Many amputee patients still have the sensation that their missing limb is still attached - Some patients may feel pain in the missing limb - For many patients, phantom limb phenomenon goes away from 2-3 years - Why? Amputated limb still has representation in the somatosensory cortex - However, not all patients experience the same phantom limb sensations - Sensation in the missing limb could be produced by touching a body part that has been appropriated the missing limb’s old “acreage” in the cortex - Cortical Reorganization Theory - Sensory input is missing for hand area due to amputation - Cells in adjacent cortical face area “take over” hand area - Physical sensation on face now activates cortical “hand” area Types of plasticity - Experimental effects of surgical manipulations, Loss of input or training on somatotopic or tonotopic maps - In healthy monkeys, digits (individual fingers) are represented separately in primary somatosensory cortex - Experiments by Merzenich & Kaas (1980s), two digits were surgically connected - Cortical map months later: digit 3 and 4 become unitary in primary somatosensory cortex - Pre-training - Tonotopic representation of 2.5 kHz in primary auditory cortex - Training manipulation: - Learn to discriminate tones in 2.5 kHz range - Recanzone (1990s) - Post training - More neurons respond to 2.5 kHz frequency range - Change in tonotopic map due to training Effects of juggling training - Increased gray matter in visual regions specialized for motion perception - Conclusion: Maps can change due to training and experience Brain response to damage and factors that influence recovery - Immediate: cell death, edema, metabolic changes, inflammation (immune response) - Effects on structure and function of adjacent areas - Within days: axon sprouting, synaptic changes, network changes (reestablishment of connections) - Factors that influence recovery - Severity of insult/injury - Number of insults/injuries and spacing between them - Age - Premorbid cognitive status - Overall brain integrity  - Extent and quality of rehabilitation The Visual System Important structures: Retina - Receptive field of vision Fovea - Small portion of the retina - Dense with photo-receptors (cones) - Responsible for sharp, clear vision Optic nerve - Bundle of nerve fibers that carry visual info from the retina to the brain Optic chiasm - Part of the brain where the optic nerves from each eye cross Optic tract - Bundle of nerve fibers that carry visual information from the optic chiasm to the brain’s lateral geniculate bodies and other parts of the brain LGN (lateral geniculate nucleus of thalamus) - Part of the thalamus that relays visual info from the retina to the primary visual cortex Superior colliculus (in midbrain/tectum) - Functions to process visual info, integrate it with other sensory inputs like auditory signals, and control eye movements to rapidly orient towards a stimulus Pulvinar - nucleus in the thalamus that plays a key role in visual processing and cognitive integration Optic radiations - the white matter tract in the brain that carries visual information from the retina to the visual cortex Primary visual cortex (a.k.a. striate cortex, V1, Brodmann’s area 17) Organization of calcarine fissure (upper and lower banks) - a deep furrow in the occipital lobe of the brain that separates the upper and lower visual fields Important Pathways: Retino-tectal - One of the Non-striate hypotheses, direct route for saccadic eye movement (retina → superior colliculus) Tecto-pulvinar - One of the non-striate hypothesis, an indirect route that bypasses the striate cortex for behavioral responses Geniculo-striate pathways - the set of axonal connections that project from the lateral geniculate nucleus (LGN) of the thalamus to the primary visual cortex. It is the single-greatest source of thalamic input to visual cortex and serves to relay visual information from retina to cortex Visual field terminology and defects: Fovea, periphery, monocular crescent - Monocular crescent: Peripheral portion of the visual field that only one eye can see - In illustration, area where lines do not overlap - The most peripheral portion of the left temporal hemifield viewed by the nasal hemiretina of the left eye - The most peripheral portion of the right temporal hemifield viewed by the nasal hemiretina of the right eye Scotoma  - General term for blind region Quadrantanopia - Deficit of ¼ of visual field - Upper or lower depends on location on calcarine fissure (homonymous) hemianopia - Deficit of ½ of the Visual Field - Same in both eyes Effects of lesions of the visual system (what lesions cause which defects?) - If lesion BEFORE the optic chiasm > deficit affects only one eye - Right hemisphere sees left visual field - If you prevent input from getting into the right hemisphere, there is no longer vision in the left visual field - If lesion occurs AFTER the optic chiasm, deficit affects the same VF in both eyes - If lesion occurs AT the optic chiasm, loss of peripheral vision in BOTH eyes Perimetry - Also known as a visual field test, is a painless, systematic measurement of the extent of a person's visual field Microperimetry - A visual field test that measures the sensitivity of the retina and maps the amount of light perceived in different areas of the retina What versus where: M and P cells, magno and parvo layers of LGN, segregation in V1 - Magnocellular Pathway (Parasol): - Input from retinal M-cells - Projects to magnocellular layers of LGN - Also projects to superior colliculus - Dominant input to dorsal/where path - Properties of magno pathway: - Fast conducting, no color code, low acuity - Parvocellular Pathway (midget) - Retinal P-cells, dominant in fovea - Projects to parvocellular layers of LGN - Dominant input to ventral/what path - Properties of parvo conducting - Slower conducting, color selective, high acuity - Many visual subregions within occipital sulci and gyri - These different subregions have different receptive field properties - “See” using the same part of the retina, but respond to different stimulus characteristics Organization: - left and right visual field (does NOT equal left and right eye) Temporal hemiretina signals stays ipsilateral - Signals from the temporal hemiretina do not cross at the optic chiasm. They travel directly to the visual cortex on the same side (ipsilateral side) of the brain. - For example, the right temporal hemiretina sends signals to the right hemisphere of the brain, and the left temporal hemiretina sends signals to the left hemisphere. - This contrasts with the nasal hemiretina, whose signals cross at the optic chiasm to reach the opposite side of the brain. - The division of visual pathways ensures that each half of the brain processes information from the opposite visual field, facilitating binocular vision and depth perception Decussation of nasal hemiretina signals foveal vision vs. peripheral vision - Signals from the nasal hemiretina capture visual information from the peripheral part of the visual field. - Decussation means crossing. Signals from the nasal hemiretina cross to the opposite side of the brain at the optic chiasm. For example: - The right nasal hemiretina sends signals to the left hemisphere of the brain. - The left nasal hemiretina sends signals to the right hemisphere of the brain. Equi-visibility and cortical magnification - Objects in the periphery must be physically LARGER to be as visible as objects falling on the fovea - Fovea is highly sensitive Upper visual field to lower bank of calcarine, lower visual field to upper bank of calcarine - Upper Visual Field information is processed in the lower bank of the calcarine sulcus (in the occipital lobe). - Lower Visual Field information is processed in the upper bank of the calcarine sulcus. - Ensures that visual input is mapped in an inverted manner in the primary visual cortex Blindsight: “residual” visual abilities of animals with striate lesions - The ability to discriminate between light and dark was spared - The ability to localize (determine where something was) was spared - Implication: Other pathways can compensate for loss of geniculo-striate function in animals “residual” visual abilities of humans with striate lesions - Residual visual function after cortex damage involving the central visual pathways in humans Implications of residual vision for parallel visual pathways - Cortical Islands Theory: spared islands of primary visual cortex are responsible for “residual” vision Poppel, Held & Frost – saccadic localization study of blindsight - Residual visual function after cortex damage involving the central visual pathways in humans Two hypotheses are. why blindsight occurs: a. Non-striate hypothesis – retino-tectal and tecto-pulvinar pathways (Superior colliculus (part of the tectum) controls eye movements) b. Cortical islands hypothesis Implications of blindsight re consciousness: primitive circuitry theory; below threshold theory - Theory 1: Primitive circuitry theory - Non striate theory: superior colliculus circuitry is too primitive to mediate awareness - Cortical processing (through C1) is necessary for conscious perception  - Theory 2: Below threshold theory - Visual signal is weak and below threshold for conscious detection - Non-striate theory: superior colliculus only gets weak retinal input - Cortical islands: tissue fragments are insufficient for consciousness What and Where Pathways: Ungerleider & Mishkin – landmark (distance) and identity discrimination tasks - Landmark Discrimination Task: This task involves identifying the location of an object (the landmark) in relation to other objects. It primarily tests spatial awareness and is associated with the dorsal stream (the "where" pathway) of visual processing. - Identity Discrimination Task: This task requires identifying an object based on its features, such as shape or color. It focuses on recognizing what the object is and is linked to the ventral stream (the "what" pathway) of visual processing. - Summary: - Landmark Task: Tests spatial awareness (dorsal stream). - Identity Task: Tests object recognition (ventral stream). Origins of the what and where pathways: magnocellular and parvocellular streams (from retina to LGN to primary visual cortex) - Magnocellular Stream (What Pathway): - Origin: Arises from magnocellular ganglion cells in the retina. - Function: Primarily processes motion and spatial information (the "where" aspect). - Pathway: Sends signals to the lateral geniculate nucleus (LGN) and then to the dorsal stream in the primary visual cortex. - Parvocellular Stream (Where Pathway): - Origin: Arises from parvocellular ganglion cells in the retina. - Function: Primarily processes color and fine detail (the "what" aspect). - Pathway: Sends signals to the LGN and then to the ventral stream in the primary visual cortex. - Summary: - Magnocellular stream: Processes motion and spatial awareness (dorsal, "where"). - Parvocellular stream: Processes color and detail (ventral, "what"). - This differentiation helps in the specialized processing of visual information as it travels from the retina to the LGN and into the primary visual cortex. Example Short Answer Questions: Name three subdivisions of the CNS. For each subdivision, (a) name one structure; and (b) describe its function. - 1. Forebrain - Structure: Cerebral Cortex - Function: The cerebral cortex is responsible for higher-order brain functions, including thought, reasoning, problem-solving, voluntary movement, and processing sensory information. - 2. Midbrain - Structure: Superior Colliculus - Function: The superior colliculus is involved in processing visual information and coordinating eye movements. It helps in orienting the head and eyes toward visual stimuli. - 3. Hindbrain  - Structure: Cerebellum - Function: The cerebellum plays a crucial role in motor control, coordination, and balance. It helps fine-tune movements and is involved in learning motor skills. - These structures exemplify the diverse functions of different regions within the CNS. Define “plasticity,” and describe three examples of plasticity. (These examples could refer to surgical manipulations, training manipulations, clinical phenomena, or mechanisms of plasticity.) - Surgical Manipulations (Brain Reorganization): - After a stroke or brain injury, some patients may experience a reorganization of brain functions. For instance, if a region responsible for motor control is damaged, other areas of the brain can take over some of its functions, allowing the patient to regain some motor abilities. This phenomenon illustrates the brain's ability to adapt structurally and functionally in response to injury. - Training Manipulations (Skill Acquisition): - When individuals engage in repetitive training, such as learning to play a musical instrument or practicing a sport, the brain undergoes plastic changes. For example, increased gray matter volume in areas of the brain associated with motor skills and auditory processing has been observed in musicians, reflecting enhanced neural connectivity and efficiency due to training. - Clinical Phenomena (Phantom Limb Sensation): - After an amputation, individuals may experience sensations in the missing limb, known as phantom limb sensations. This occurs due to reorganization in the brain's sensory cortex, where the area previously dedicated to the missing limb may become responsive to other body parts. This reorganization illustrates how the brain adapts to changes in the body, maintaining a representation of the lost limb.