Higher Cortical Functions

Question 1

How is the cerebral cortex arranged?

Answer 1

Arranged in 6 layers containing containing cell bodies and dendrites (i.e. cortex is grey matter)

Question 2

What are most outputs from the cortex?

Answer 2

They more mostly axons of pyramidal neurones (e.g. upper motor neurones in the primary motor cortex are pyramidal neurones)

Outputs can be projection fibres going down to the brainstem and cord (e.g. upper motor neurones)

Outputs can be commisural fibres going between hemispheres (e..g Corpus Callosum)

Outputs can be association fibres connecting nearby regions of cortex in the same hemisphere (e.g. accurate nucleus)

Question 3

Where do most inputs to the cerebral cortex come from?

Answer 3

Thalamus and other cortical areas.

An important population of inputs arise from the reticular formation, maintaining cortical activation (consciousness).

Question 4

What does the frontal lobe do?

Answer 4

Motor - primary motor cortex and associated areas. If damage = contralateral weakness.

Expression of speech (usually left hemisphere) - Broca’s area damage = expressive dysphagia

Behavioural regulation / judgement - Prefrontal cortex. Damage = impulsive, disinhibited behaviours e.g. sexual inappropriateness, aggression

Cognition - Prefrontal Cortex. Damage (right) = difficulty with complex problem solving and calculation

Eye movements - Frontal eye fields. Damage = problems with conjugate gaze and other eye movement disturbances.

Continence - Contain cortical areas for the maintenance of continuance (paracentral lobules). Damage = Urinary incontinance

Question 5

What does the parietal lobe do?

Answer 5

Sensory - Contains primary sensory cortex and associated areas. Damage = contralateral anaesthesia affecting all modalities.

Comprehension of speech = Contains part of Wenicke’s area. Damage left parietal lobe = receptive dysphagia

Body image and awareness of external environment = involved with acknowledgement that things exist. Damage = neglect

Calculation and writing = work with frontal lobe. Damage to left parietal lobe can affect this.

Superior optic radiations go through here. Damage = contralateral inferior homonymous quadrantanopia.

Question 6

What does the Temporal lobe do?

Answer 6

Hearing - Primary auditory cortex on superior surface near Wernicke’s area. Damage = hearing effects or auditory hallucinations.

Olfaction - Primary olfactory cortex on the infero-medial temporal lobe. Damage = Complex smell effects or olfactory hallucinations.

Memory - Hippocampus. Damage = amnesia (we but, we have two, one in each lobe).

Emotion - limbic system e.g. hippocampus and amygdala. Complex but related to pathogenesis of psychiatric disorders.

Inferior optic radiations through here. Damage = contralateral superior homonymous quadrantanopia.

Question 7

What hemisphere is most dominant for language and mathematical / logic functions?

Answer 7

For 95% of people the let hemisphere is dominant for language and mathematical / logic functions.

Question 8

What hemisphere is the most dominant for body image, visuospatial awareness, emotion and musical ability.

Answer 8

In 95% of people the left hemisphere is dominant for body image, visuospatial awareness, emotion and musical ability.

Question 9

How do two hemispheres communicate?

Answer 9

Corpus Callosum

Question 10

What can happen if the corpus Callosum gets damaged?

Answer 10

Destruction of the corpus Callosum can lead to interesting deficits such as alien hand syndrome and subtle effects on language and processing.

Question 11

Where is Broca’s area? What is this near?

Answer 11

Inferno-Lateral frontal lobe near the mouth and pharynx areas of the primary motor cortex.

Question 12

What does Broca’s area do?

Answer 12

Broca’s area is responsible for the production of speech.

Question 13

What happens if you damage Broca’s area?

Answer 13

Causes staccato speech, where the patient still understands what is being said to them.
(Broca’s / expressive dysphagia.)

Question 14

Where is Wernicke’s area? What is this near?

Answer 14

At the parieto-temporal junction near to the primary auditory cortex in the temporal lobe.

Question 15

What is Wernicke’s area responsible for?

Answer 15

The comprehension of speech.

Question 16

What happens if Wericke’s area is damaged?

Answer 16

Damage causes fluent, nonsensical speech where the patient does not seem to understand what is being said to them.
(Broca’s / receptive dysphagia)

Question 17

How could both Broca’s and Wernicke’s area be destroyed?

Answer 17

Large middle cerebral artery infarct can cause a dense / global aphasia where both area’s are destroyed leading to virtually no language function.

Question 18

What connects Broca’s and Wernicke’s areas?

Answer 18

They are connected by the arcuate fasiculus.

Question 19

What happens if the arcuate fasiculus is damaged?

Answer 19

Damage to the arcuate fasiculus can cause the inability to repeat heard words.

Question 20

Where are memories stored?

Answer 20

Memories are believed to be stored across wide areas of the brain.

Question 21

What are the different types of memory?

Answer 21

Declerative / explicit - Factual information (stored in cerebral cortex).

Nondeclarative / simplicity - motor skills, emotions (stored in subcortical structures e.g. basal ganglia and cerebellum).

Short term memory - stored for seconds to minutes as a ‘reverberation’ or ‘echo’ in cortical circuits.

Long term memory - stored for very long periods in the cerebral cortex, cerebellum ect. (up to a lifetime) following consolidation.

Question 22

What factors influence consolidation?

Answer 22

Emotional context (if an event has strong emotional content, then it tends to be remembered better).

Rehearsal

Association (if you can associate a price of knowledge with something you already know, it is more easily remembered).

Question 23

What consolidates declarative memories?

Answer 23

The hippocampus helps to consolidate declarative memories.

Question 24

Where is the hippocampus?

Answer 24

The hippocampus sits deep in the temporal lobe (it is the rolled medial edge of the temporal lobe).
It has multimodal inputs from many brain systems (good at associating stimuli).
It has a role as an oscillator, facilitating consolidation of memories in the cortex visits output pathways (primarily in the fornix -> Mammilary bodies -> thalamus -> cortex

Question 25

What is long term potentiation?

Answer 25

This is a key molecular mechanism in memory consolidation,

It causes changed in glutamate receptors in synapses leading to synaptic strengthening.

New physics connections can also form between neurones to further strengthen the connections (axonal sprouting).