Higher Cortical Functions & Cognitive/Behavioral Manifestations of Brain Disorders PDF

Higher Cortical Functions & Cognitive / Behavioral Manifestations of Brain Disorders 7th Ed Reading: Pages 10-12,16-17, 366- 370, 374, 382-384, 388-394, 421-422, 427, 440-446, 449-452, 575-580, 586, 607-609. Chapter 18 & 19 8th Ed Reading: Pages 9-11, 15, 337-341, 345, 352-354, 357,...

Higher Cortical Functions & Cognitive / Behavioral Manifestations of Brain Disorders 7th Ed Reading: Pages 10-12,16-17, 366- 370, 374, 382-384, 388-394, 421-422, 427, 440-446, 449-452, 575-580, 586, 607-609. Chapter 18 & 19 8th Ed Reading: Pages 9-11, 15, 337-341, 345, 352-354, 357, 363, 390-391, 395, 418, 528-530, 535, 538, 544, 554-556.  Brief Summary of Neocortical Function Primary Areas: Project to spinal motor systems or receive sensory input (via thalamus)  Brief Summary of Neocortical Function Secondary Areas: Adjacent to primary areas Sensory: Primary  Secondary Motor: Secondary  Primary  Brief Summary of Neocortical Function Tertiary Areas: Aka Association Cx Located between secondary areas Not specific to sensory or motor  Examples of “Higher-Order” Functions Language Memory Executive Functions Perception Spatial Behaviour Attention Skilled Movement  Main Anatomical Areas Associated with Language Left hemisphere Broca’s area (green) – Located in the frontal operculum Wernicke’s area (yellow) – Located in the superior temporal gyrus Aka “perisylvian” areas – **specialized  Main Anatomical Areas Associated with Language Broca’s area (areas 44 & 45) Wernicke’ s area (area 22) Wernicke-Geschwind Model (1960’s & 70’s) Arcuate fasciculus: important for repetition (combines both production & comprehension) Revisions to Wernicke-Geschwind Model Original model is conceptually useful but details have been substantially revised by improved lesion analysis and neuroimaging Current models adopt network approach (not linear) Functions may be represented diffusely, e.g., semantics is not just in Wernicke’s area Broca’s area contains mental representations of language (not  Disorders of Language Aphasia is an acquired disorder of language apparent in speech (production &/or comprehension), reading (i.e., dyslexia/alexia) &/or writing (i.e., dysgraphia/agraphia) Often results from stroke (> 80% of cases) but also from brain injuries, tumors, infections, dementias, etc.  Aphasia May be broadly classified into: Disorders of Comprehension (i.e., fluent types) Disorders of Production (i.e., nonfluent types)  Wernicke’s Aphasia Difficulty in comprehending & repeating speech produced by other people or oneself Language production is generally fluent (i.e., no articulation problems) but jargon-like (over-used phrases that may be out of context) and may include neologisms (nonword errors but relationship cannot be seen), paraphasias (word errors, but relationship can be seen), and word  Wernicke’s Aphasia Q: What kind of work did you do before you came into hospital? A: Never, now mista oyge I wanna tell you this happened when happened when he rent. His – his kell come down here and is – he got ren something. It happened. In these ropiers were with him for hi – is friend – like was. And it just happened so I don’t know, he did not bring around anything. And he did not pay it. And he roden all o these arranjen from the pedis on from iss pescid. In these floors now and so. He hadn’t had em around here.  Anomic Aphasia Mildest form of aphasia. Often is a residual deficit after recovery. Isolated difficulty in finding names of specific words or objects Language comprehension, production and repetition are relatively intact Circumlocutions are common Q: What is this? (picture of igloo) A: I know what it is, it’s made of snow. People in the Arctic live in them or use them as shelter… Results from variable lesion sites (often in left temporal and/or frontal lobes) Anomia is a symptom of many aphasia types but  Broca’s Aphasia Most common aphasia seen clinically Difficulty in the production of language (i.e., mental representations, not motor). Speech (when produced) is slow, labored and telegraphic. Comprehension is relatively good but may have difficulty with syntactically- complex phrases Insight into linguistic abilities usually preserved  Broca’s Aphasia Q: Why did you come to the hospital? A: Ah…Monday…ah Dad and Paul…and Dad… hospital. Two…ah doctors…and ah…thirty minutes…and yes…ah hospital. And er Wednesday…nine o’clock…doctors. Two doctors…and ah…teeth. Yeah…fine.  Global Aphasia Generalized difficulty in comprehending, producing or repeating speech (some automatic phrases may be spared) Usually results from extensive left- hemisphere lesions  Dysarthria Distinct from aphasia and is not a language disorder Refers to speech disorders that result from neuromuscular (motor) dysfunction Nature of motor-speech deficits depend on what part of system the dysfunction arises in Examples: Upper motor neurons Lower motor neurons (ie., cranial nerves)  Classification of Memory Systems Different memory systems have different neural substrates  Main Anatomical Areas Associated with LT Explicit Memory Temporal lobe and proximal areas Prefrontal cortex – Helps piece events together for memories Medial thalamus  Main Anatomical Areas Associated with Explicit Memory  Main Anatomical Areas Associated with Memory LTM Explicit: Prefrontal cortex- temporal lobe structures-medial thalamus circuit LTM Implicit: Basal ganglia &/or cerebellum-neocortex circuit Disorders of Memory Different memory systems will be impaired by different types of brain damage Amnesia = Loss of memory Anterograde vs. Retrograde amnesia Case HM (1926-2008) Severe anterograde amnesia for explicit memories following bilateral medial temporal lobe resection  Material-Specific Amnesias Left and right hemispheres are involved in encoding and retrieving different types of material Lesions in left hemisphere can impair memory for verbal material (language- based), e.g., names, stories.  Material-Specific Amnesias Lesions in right hemisphere can impair memory for visual/spatial material (e.g., faces, routes, locations) Example from patient with tumor in right temporal lobe:  Frontal-Lobe Function Primary motor, premotor and prefrontal areas Prefrontal areas (i.e., dorsolateral & orbitofrontal) associated with “executive functions”  Executive Function(s) Refers to “control systems that implement different behavioural strategies in response to both external and internal cues” (Kolb & Whishaw) Includes an extensive variety of functions Frontal damage is unlikely to produce impairment to all functions Lots of variability between patients  FL Symptom Examples Impaired social behaviour and changes in personality Case: Phineas Gage  FL Symptom Examples Not the same as aphasia; just a loss of behavioural motivation Loss of behavioral spontaneity (e.g., loss of initiative/motivation, apathy, decreased verbal fluency)  FL Symptom Examples Poor strategy formation, loss of response inhibition & perseveration Wisconsin Card Sorting Task  Many Etiologies Can Affect Frontal Lobe Functions Direct FL lesions (e.g., TBI, stroke, AD & other degenerative conditions) Lesions to subcortical areas that project to FL (e.g., stroke, PD, HD)