Cortical structures & lateralisation of function

Question 1

State the techniques used to obtain information about differences across the cortex

Answer 1

1. Straining techniques e.g. nissi straining
2. Lesion studies
   
   • Experimental animals- lesion cortical areas- study effect on behaviour

Question 2

State the techniques used to obtain information about differences across the cortex

Answer 2

1. Straining techniques e.g. nissi straining
2. Lesion studies:
   
   • Experimental animals- lesion cortical areas- study effect on behaviour
   • Humans- examine behaviour after pathology, surgery, accidents
3. Electrophysiology: electroencephalography (EEG)
4. Imaging studies: CT and MRI scans, PET & fMRI imaging

Question 3

Explain how Cytoarchitecture works.

Answer 3

• From histological analysis of cortex
• Neocortex: 6 layers
• Hippocampus: 3-4 layers
• Areas that receive sensory information have a wide lamina IV
• Areas that send out MOTOR information have a wide lamina V

Question 4

State where Brodmann’s areas are.

Answer 4

1. Somatosensory (primary) cortex: areas 1, 2, 3
2. (Primary) motor cortex: area 4
3. (Primary) visual cortex: area 17 & 18
4. (Primary) auditory cortex: area 41 & 42
5. Speech areas: 44 & 45 (Broca’s Area)

Question 5

State where Brodmann’s areas are.

Answer 5

1. Somatosensory (primary) cortex: areas 1, 2, 3
2. (Primary) motor cortex: area 4
3. (Primary) visual cortex: area 17 & 18
4. (Primary) auditory cortex: area 41 & 42
5. Speech areas: 44 & 45 (Broca’s Area)

Question 6

Describe what the association cortex is & its function

Answer 6

1. Primary sensory/ motor cortices occupy only small fraction of total cortex- remainder (75%) is “association cortex”
2. Function- to integrate information from other areas

Question 7

Provide key facts about the Association cortex.

Answer 7

1. Very large in humans- used to be known as “silent” areas, they do not produce motor or sensory effects when stimulated.
2. Input: Primary/ Secondary sensory & motor cortices; other association areas (both hemispheres); thalamus & brainstem.
3. Outputs: hippocampus, basal ganglia/ cerebellum, thalamus & other association cortices.
4. Role: Cognition (the process by which we come to know the world)
   - ability to attend to external stimuli or internal motivation
   - to identify the significance of such stimuli
   - to plan meaningful response to them

Question 8

Describe & Explain the association cortex connections

Answer 8

slide 8

Question 9

Visual association cortex

Answer 9

Dorsal & Ventral Visual Streams

1. Dorsal:
   - Striate cortex to parietal lobe
   - Spatial vision, analysis of motion
   - Positional relationships of objects
   - Cerebral akinetopsia
2. Ventral:
   - Striate cortex to temporal lobe
   - High resolution form vision
   - Object recognition

Question 10

State 2 key facts about the parietal association cortex

Answer 10

1. Lesions in this area lead to deficits of attention
2. Contralateral neglect syndrome: inability to perceive and attend to objects, or even ones own body, in part of space e.g. An artist who has suffered parietal stroke on right side- it could take them up to 9 months months to recover and draw their own faces correctly.

Question 11

State 3 key facts about the temporal association cortex?

Answer 11

1. It is involved in the recognition of objects and memory
2. Lesions in this area result in deficits in recognition
3. Selective activation of face cells in inferior temporal cortex

Question 12

What is prosopagnosia?

Answer 12

• “face blindness”
• affects systems specific to visual processing of facial identity
• data supports idea that there are separate processing areas for faces and for other objects
• but why is the face so important?

Question 13

Explain frontal association cortex and a study to go with it

Answer 13

Prefrontal cortex is involved in planning.
Contains “planning” or “delay-specific” neurones

• Delayed response tasks:
  If a monkey is shown 2 bowls, one with food and one empty.
  These bowls are covered up. There is a delay and then the monkeys are allowed to uncover the bowls and get the food.

If the prefrontal cortex (area anterior to motor cortex) is lesioned in the monkey, they cannot perform the task (i.e. they cannot identify which bowl has the food).

Question 14

What is lateralisation of speech?

Answer 14

a.k.a. Hemispheric lateralisation

In most people- speech centres are found in the LEFT hemisphere
Damage to these centres result in aphasia (reduced ability to produce/ comprehend language).

Broca area: Lesions affect language production -> halting speech, disordered, repetitive

Wernicke’s area: Lesions cause the individual to speak fluently but make little sense. (reflects damage to auditory cortices) -> fluent, little repetition, ordered but inappropriate/ contrived words

Question 15

What is aphasia and split brain?

Answer 15

https://www.youtube.com/watch?v=lBqShvm4QRA
https://www.youtube.com/watch?v=aCv4K5aStdU

Split brain allows to evaluate each hemisphere independently.

It provides information to one side of the brain only.
e.g. ask oatient to identify objects from each hand without visual information

Objects held in right hand (somatosensory info goes to left hemisphere) are easily named

Objects held in left hand cannot be named easily (“ball” becomes “a round thing”)

Conclusion: language specialisation is in the left cerebral hemisphere.