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BB7 - Higher Cortical Function
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What parts of brain mediate between the demands of the internal milieu and the constraints of the environment? (2)


  • Heteromodal area
  • Paralimbic area



Aspects of cognition can be divided how? (2)


  • State
  • Channel



What are the state aspects of cognition? (4)


  • Arousal
  • Attention
  • Mood
  • Motivation

Abnormalities with these can profoundly confound exam results


What are the channel aspects of cognition? (4)


  • Language
  • Memory
  • Visuospatial function
  • Somatomotor function



Define attention


Ability to maintain and engage in salient stimuli in consciousness while extruding irrelevant perceptions, thoughts and feelings


What parts of brain are involved in attention?



Attention is mediated by a distributed network of brainstem, basal ganglia, thalamic and cortical structures
  • Cortical: Reticular modulation of ascending sensory info
  • Frontal lobes: Selective attention
  • Paralimbic: Emotion & screening of stimuli
  • Parietal: Shifting focus of attention
  • Distributed cortical network: Required for conscious awareness

Also consciousness requires voluntary effort


What is the attentional matrix?


  • Bedrock of cognition
  • Attention presupposes arousal and alertness
  • Has both state and channel components



Delirium is a prototypical disorder of what?


Attention


  • What causes delirium? (2)
     
  • Why is it a concern? (2) 



  • Often iatrogenic or result of undiagnosed medical illness
     
  • Increased mortality rate and increased risk of complications



What is delirium?


Confusional state + illusions, hallucinations (especially visual, tactile)
  • Severe attentional disturbance 



Describe other features of delirium? (7)


  • Distractibility
  • Impaired vigilance and orientation
  • Disorientation (as indicator of severity)
  • Fluctuating arousal/somnolence
  • Fragmentation of thought and action
  • Perseveration: Repetition of a response in absence of eliciting stimuli
  • Moment-to-moment fluctuation in peformance on cognitive tests



Provide a differential diagnosis for delirium? (14)


Stroke
Toxic
Autoimmune
Thyroid

Vitamin
Infection
Trauma
Alzheimer's
Liver, kidney, cardiac

Surgery
Iatrogenic
Geriatric
Neoplasia
Seizures


What is hemispatial neglect?


Persistent failure to detect, respond, or to orient to relevant stimuli, or to initiate appropriate movements in a hemispace
  • Unexplained by primary sensory or motor defects 



  • Hemispatial neglect is usually on which side?
  • What would cause this? 



  • Usually left-sided neglect
  • Due to a R hemisphere lesion



Describe the following types of memory in terms of riding a bike:
  • Episodic
  • Semantic
  • Procedural
  • Working 



  • Episodic: The last time you rode a bike
  • Semantic: Knowing what a bike is
  • Procedural: Knowing how to ride a bike
  • Working: Taking bike lock key, and house key, on way to ride bike



What part of the brain is involved in semantic memory?


Inferolateral temporal lobe


What parts of the brain are involved in procedural memory? (3)


  • Basal ganglia
  • Cerebellum
  • Supplementary motor area



What parts of the brain are involved in working memory?


Prefrontal cortex
  • Verbal (left prefrontal)
  • Visuospatial (right prefrontal) 



Episodic memory is the memory system for what? (2)


  • Temporally specific events
  • Episodes that are "personally experienced"



What are bedside tests for episodic memory? (5)


  • Recent event recall
  • Word lists (5-word MoCA list)
  • Paragraph recall
  • 3-word 3-shape test
  • 3-bedside objects and locations



Episodic memory is in what part of the brain anatomically? (2)


Episodic mesial temporal lobes:
  • Hippocampus
  • Parahippocampal gyrus 
And:
  • Fimbria/fornix
  • Mammillary bodies
  • Mammillothalamic tract
  • Anterior thalamic nuclei
  • Cingulate gyrus



What happened to the patient HM?


Had his mesial temporal lobes resected, had severe persistent anterograde amnesia
  • Episodic memory destroyed 



What is alexia?


When a person cannot understand written words


What is praxis?


Ability to perform a learned/skilled motor sequence


What is apraxia?


Loss of praxis (ability to perform learned/skilled motor sequence)
  • Absence of causative motor or sensory deficit
  • Intact comprehension, attention, motivation



What are 3 types of apraxia?


  • Limb kinetic (slow, stiff movements)
  • Ideomotor
  • Ideational 



What is ideomotor apraxia?


Failure to perform skilled/learned motor sequences on command or to imitation
  • Screening: "Show me how you would brush teeth, comb, salute..."
  • Errors: Body part as an object
  • Attempt usually recognizable



What is ideational apraxia?


Difficulty in performing a sequence of steps to complete a task
  • Loss of knowledge to select tools or objects 



What is agnosia?


Impaired higher level recognition in the presence of preserved elementary perception, memory and general intellect
  • It is the loss of ability to recognize objects, persons, sounds, shapes, or smells 



Name 2 types of visual agnosia


  • Apperceptive
  • Associative



What is apperceptive agnosia?


  • Shape perception abnormal (worse in geometric figures, pictures)



What is associative agnosia?


  • Relatively intact perception, poor recognition (cannot match or describe by sight)



What is prosopagnosia?


Loss of face recognition
  • Associated with left hemifield deficit
  • Localized to medial occipitotemporal cortex



What usually causes prosopagnosia?


Infarct to right PCA


What are some of the functions of the frontal lobe? (6)


  • Divided attention
  • Aspects of langauge and memory
  • Abstraction
  • Association and mental synthesis
  • Judgement
  • Conceptual planning



What are 4 behavioural functions of the frontal lobe?


  • Motor activation (apathy)
  • Aspects of personality
  • Social judgment and demeanor
  • Personal hygiene 



What is orbitofrontal syndrome?


What happens when the orbitofrontal area of the brain is damaged
  • Behavioral variant of frontotemporal dementia (head injury) 



What are the effects of the orbitofrontal syndrome? (functions, behavioral)


Function
  • Disinhibition
  • Impulsive behaviour
  • Distractible
  • Emotional lability, irritable
  • Inane euphoria
Behaviour
  • Jocularity
  • Poor judgment and insight
  • Hyperactive/manic
  • Sexual preoccupation



Which famous patient had orbitofrontal syndrome?


Phineas Gage


Dorsolateral frontal syndrome leads to problems with what? (1)


Executive function


Describe dorsolateral frontal syndrome in terms of function (4) and behaviour (4)


Function
  • Reduced verbal, non-verbal fluency
  • Perseveration
  • Abstraction impaired
  • Retrieval deficits
Behaviour
  • Poor set shifting
  • Poor strategies on copying tasks
  • Impaired attention
  • Depressed mood



What can cause dorsolateral frontal syndrome?


  • Penetrating head injury
  • Frontal lobe infarcts



For medial frontal syndrome, what is the primary feature? Give some other important features.


Apathy/Unmotivated
  • Emotional emptiness
  • Failure to implement new plans
  • Loss of generative thought
  • Decreased motor activity



What can cause medial frontal syndrome?


  • ACA/MCA border zone infarcts
  • Ruptured ACA aneurysms 



What tests can be used for frontal lobe function in general? (3)


  • Letter fluency tasks: generate words beginning with a given letter
  • Non-verbal ("design" fluency) tasks: generate designs
  • Sequential motor tasks