Functional organisation of Cerebral Cortex

Question 1

What are the 3 primary brain vesicles?

Answer 1

• Forebrain
• Midbrain
• Hindbrain

Question 2

What are the 4 lobes of the cerebral cortex?

Answer 2

• Frontal
• Temporal
• Parietal
• Occipital

Question 3

What are the constituents of the forebrain?

Answer 3

Cerebral Hemisphere

• Cerebral cortex
• Basal Ganglia
• various small nuclei
• Olfactory Bulb.

Diencephalon

• Thalamus
• Subthalamus
• Hypothalamus
• Epithalamus

Question 4

What are the 6 cortex’s within the cerebral cortex?

Answer 4

• Somatosensory cortex
• Motor cortex
• Premotor cortex
• Visual cortex
• Auditory cortex
• Olfactory cortex

Question 5

Motor cortex;

• Where is it located in the brain
• What is its sub components?
• Where are they located?
• What’s their roles?

Answer 5

• Located in front of the central sulcus
• It’s a primary cortex aka primary motor cortex, this means it has sub components;
• Supplementary motor cortex; this is located medially, and has bilateral representation of the body.
  Involved in the planning/ preparation of movement.

On the lateral surface there is the Premotor cortex. Largely devoted to trunk muscles and so is important to posture

• Both these sub-cortices contribute 25/30% to upper motor neurons, coccygeal, spinal and corticobulbar fibres.

Question 6

What is the difference between injury to PMC vs its sub-cortices?

Answer 6

If we stimulate the PMC we will stimulate a discrete muscle group contraction on the opposite side of the body, if you stimulate secondary areas you get a much more elaborate movement where functionally related muscle groups are stimulated.

So if you damage to PMC e.g. stroke then you will end up with spastic paralysis and hyperreflexia where as if you damage a secondary areas then you get a very different phenotype e.g. gasping reflexes.

Question 7

Somatosensory cortex

• What’s it also known as?
• What happens if PSC is damaged?
• What happens if superior parietal lobe vs inferior lobe is damaged?

Answer 7

• Post central gyrus = primary somatosensory cortex, the rest of the parietal lobe = supplementary somatosensory cortex which does more elaborate processing.
• Damage to PSC = somatosensory anaesthesia, which means you’ve lost touch, no feeling.

But damage to the PSC’s supplementary cortices, then it’s very different.

• Damage to superior parietal lobe = somatosensory agnosia, this is where you loose touch and proprioception on the contralateral side. So, you’re unable to identify common objects by palpation alone.
• Damage to inferior parietal lobe = depends if it’s on the (dominant) hemisphere which is language dominant (usually L). If yes then you’ll be mute. But if no, then you have disturbances in body imagery = somatosensory neglect. So, a patient may not consider their left leg as part of their body, despite that it’s sensitive to touch, they’ll actively ignore it and try to get rid of it.

Question 8

Visual cortex

• What is it made up of?
• What is the secondary visual cortex?

Answer 8

• The PVC is formed by the upper and lower limbs of the calcarine sulcus.
• The rest of the occipital lobe is the secondary visual cortex.

Question 9

Damage to the supplementary areas of the visual cortex can lead to which disorders?

Answer 9

• Visual agnosia; inability to recognise everyday objects
• Visual disregard; Lesion of non-dominant inferior parietal lobule.
• Loss of face recognition

Question 10

Auditory cortex

Answer 10

-Located between Broca’s and Wernicke’s areas.

Question 11

What is the result of injury to Broca’s area?

Answer 11

Patient knows what they want to say but cannot do it with grammar.

Question 12

What is the result of damage to Wernicke’s area?

Answer 12

Perfect grammar but meaningless.

Question 13

Result of damage to right hemisphere?

Answer 13

Loss of ability to interpret emotional content.