Neuro12 - Cortical Function

Question 1

4 general features of the cerebral cortex

Layers
Outputs x3
Inputs x2
Interneurones

Answer 1

1. ) Layers - grey matter arranged in 6 different layers
   - contains cell bodies and dendrites
2. ) Outputs - 3 types of fibres from cortex to:
   - projection: brainstem and spinal cord (e.g. UMNs)
   - commisural: connects hemispheres (corpus callosum)
   - association: nearby reigons of cortex in same hemisphere (e.g. arcuate fasciculus)
3. ) Inputs - from thalamus and other cortical areas
   - from reticular formation to maintain cortical activation
4. ) Interneurones - connects inputs and outputs
   - gives rise to behaviour, emotion, memory etc.

Question 2

4 features of cerebral dominance

What is it?
Normal Cerebral Dominance
Visuospatial Awareness
Corpus Callosum

Answer 2

1.) What is it? - some functions are represented more prominently in one hemisphere than the other

2. ) Normal Cerebral Dominance - 95% of people
   - left hemisphere deals with sequential processing (e.g. language, mathematics, logic)
   - right hemisphere deals with ‘whole picture’ processing (e.g. body image, emotion, musical ability)
3. ) Visuospatial Awareness
   - right hemisphere deals w/ R and L side of space
   - left hemisphere only deals with the R side of space
   - damage to right hemisphere –> loss of L side of space
4. ) Corpus Callosum - lets hemispheres communicate
   - supplied by the anterior cerebral artery
   - damage –> alien hand syndrome
   - language areas in left hemisphere so if corpus callosum is damaged, you cannot verbally name objects from the the left visual field (right hemisphere) because information cannot reach the language areas

Question 3

4 features of language pathways

Broca’s Area
Wernicke’s Area
Arcuate Fasciculus
Large MCA Infarct

Answer 3

1. ) Broca’s Area - infero-lateral frontal lobe
   - sits near to the mouth/pharynx area of the PMC
   - responsible for the production of speech
   - damage –> staccato speech, where the patient still understands what is being said (expressive dysphasia)
2. ) Wernicke’s Area - parieto-temporal junction
   - sits near to the PAC in the temporal lobe
   - damage –> fluent, nonsensical speech, where patient doesn’t understand what is said (receptive dysphasia)
3. ) Arcuate Fasciculus - connects both areas together
   - damage –> inability to repeat heard words
4. ) Large MCA Infarct - damages both areas
   - blockage of superior and inferior MCA
   - global aphasia: no verbal language function

Question 4

4 types of memory and their storage

Declarative/Explicit
Nondeclarative/Implicit
Short Term
Long Term

Answer 4

1. ) Declarative/Explicit - factual information
   - stored in the cerebral cortex
2. ) Nondeclarative/Implicit - motor skills and emotion
   - stored in subcortical structures e.g. basal ganglia and cerebellum
   - cerebellum is responsible for consolidation
3. ) Short Term - seconds to minutes
   - stored as reverberations/echoes in cortical circuits
4. ) Long Term - up to a lifetime
   - stored in the cerebral cortex, cerebellum etc following consolidation

Question 5

3 features of memory consolidation

What is it?
Hippocampus
Long Term Potentiation

Answer 5

1. ) What is it? - converts short –> long term memories
   - influences: emotional context, rehearsal, association

2.) Hippocampus - consolidates declarative memories
- has multimodal inputs from many brain systems making it very good at associating stimuli
- oscillator role: consolidates memories via its outputs:
fornix –> mammillary bodies –> thalamus –> cortex

3. ) Long Term Potentiation - molecular mechanism
   - causes changes in glutamate receptors in synapses leading to synaptic strengthening
   - axonal sprouting: new physical connections form between neurones to further strengthen connections

Question 6

6 functions of the frontal lobe

Motor
Expression of Speech
Behaviour
Cognition
Eye Movements
Continence

Answer 6

1. ) Motor - PMC in pre-central gyrus
   - damage results in contralateral muscle weakness
2. ) Expression of Speech - function of Broca’s area
   - usually found in the left hemisphere
   - damage to left frontal lobe –> expressive dysphasia
3. ) Behaviour - function of prefrontal cortex
   - damage can lead to impulsive, disinhibited behaviours e.g. sexual inappropriateness or aggression
4. ) Cognition - function of prefrontal cortex
   - damage (esp. right side) can cause difficulty with tasks such as complex problem solving and calculation
5. ) Eye Movements - function of frontal eye fields
   - damage can cause problems with conjugate gaze and other eye movement disturbances
   - diplopia w/out cortical features suggests CN lesion
6. ) Continence - function of paracentral lobules
   - contains UMNs for urethral and anal sphincter
   - damage can cause urinary incontinence

Question 7

5 functions of the parietal lobe

Sensory
Comprehension of Speech
Calculation and Writing
Body Image and Awareness of External Environment
Contains Superior Optic Radiations

Answer 7

1. ) Sensory - primary sensory cortex in post-central gyrus
   - damage causes contralateral anaesthesia affecting all modalities
2. ) Comprehension of Speech - function of Wernicke’s
   - Wernicke’s area found in the left hemisphere
   - damage to left paretal lobe –> receptive dysphasia
   - affects both spoken and written speech
3. ) Calculation and Writing - works w/ frontal lobe
   - controlled by the left hemisphere
   - damage to left parietal lobe –> ↓calculation ability
4. ) Body Image and Awareness of External Environment
   - acknowledgement that things (inc body) exist
   - right hemisphere responsible for both left and right side
   - left hemisphere only responsible for right side of space
   - damage to right parietal lobe –> hemispatial neglect (left side)
5. ) Contains Superior Optic Radiations
   - not a cortical function and in both hemispheres
   - damage –> contralateral inferior homonymous quadrantanopia

Question 8

5 functions of the temporal lobe

Hearing
Olfaction
Memory
Emotion
Contains Inferior Optic Radiations

Answer 8

1. ) Hearing - contains primary auditory cortex (PAC)
   - PAC on superior surface, near to Wernicke’s area
   - damage –> number of effects on hearing including auditory hallucinations
2. ) Olfaction - contains primary olfactory cortex (POC)
   - POC on infero-medial aspect of temporal lobe
   - damage –> number of effects on smell including olfactory hallucinations
3. ) Memory - contains hippocampus (x2)
   - sits in rolled medial edge of the temporal lobe
   - damage –> amnesia, temporal lobe epilepsy can trigger memories –> deja vu
4. ) Emotion - contains limbic system structures such as the hippocampus and the amygdala
   - damage –> pathogenesis of psychiatric disorders
5. ) Contains Inferior Optic Radiations
   - not a cortical function
   - damage –> contralateral superior homonymous quadrantanopia