Higher cortical function

Question 1

What is the fine structure of the cerebral cortex?

Answer 1

• Arranged as 6 layers containing cell bodies and dendrites

Question 2

What are most outputs of the cortex?

Answer 2

• Axons of pyramidal neurones
• E.g. upper motor neurones in the primary motor cortex

Question 3

Give some examples of outputs of the cortex?

Answer 3

• Projection fibres going down to the brainstem and cord e.g. upper motor neurones
• Commissural fibres going between the hemispheres e.g. corpus callosum
• Association fibres connecting nearby regions of the cortex in the same hemisphere e.g. arcuate fasciculus

Question 4

Where do most inputs to the cortex come from?

Answer 4

• Thalamus and other cortical areas
• An important population of inputs arise from the reticular formation, maintaining cortical activation (consciousness)

Question 5

What is the function of interneurones?

Answer 5

• Connect inputs and outputs in a complex way
• Gives rise to behaviour, emotion, memory etc.

Question 6

What are the frontal lobe functions?

Answer 6

• Primary motor cortex and associated areas
• Expression of speech (usually left hemisphere) because Broca’s area is here
• Behaviour regulation/judgement and cognition (prefrontal cortex)
• Eye movements (frontal eye fields)
• Continence (paracentral lobules)

Question 7

What happens when the frontal lobe is damaged?

Answer 7

Impulsive and disinhibited behaviours
- Difficulty with tasks such as complex problem solving and calculations
- Problems with conjugate eye movement

Question 8

Where is the primary motor cortex located and what can damage to this area cause?

Answer 8

• Frontal lobe
• Contralateral motor weakness

Question 9

Where is Broca’s area located and what can damage to this area cause?

Answer 9

• Damage to left frontal lobe can result in expressive dysphagia

Question 10

Where is the prefrontal cortex located and what can damage to this area cause?

Answer 10

• Frontal lobe
• Impulsive, disinhibited behaviours e.g. sexual inappropriateness and aggression
• Difficulty with tasks such as complex problem solving, including calculation

Question 11

Where are the frontal eye fields located and what can damage to this area cause?

Answer 11

• Frontal lobe
• Problems with conjugate gaze and other eye movement disturbances (diplopia without other cortical features suggests brainstem/cranial nerve problem)

Question 12

Where are the paracentral lobules located and what can damage to this area cause?

Answer 12

• Frontal lobe
• Urinary incontinence

Question 13

What are the functions if the parietal lobe?

Answer 13

• Sensory
• Comprehension of speech
• Body image and awareness of external environment
• Calculation and writing

Question 14

Where is the primary sensory cortex located and what can damage to this area cause?

Answer 14

• Parietal lobe
• Contralateral anaesthesia affecting all modalities

Question 15

Where is Wernicke’s area located and what can damage to this area cause?

Answer 15

• Left parietal lobe
• Receptive dysphasia

Question 16

Why does damage to the parietal lobe cause neglect?

Answer 16

• Parietal lobe is involved in acknowledgement that things (including the body) exist
• Involved in body image

Question 17

How does the parietal lobe contribute to calculation and writing?

Answer 17

• Works with frontal lobe to perform these tasks
• Damage to left parietal lobe can affect calculation ability

Question 18

How is the parietal lobe involved in the visual pathways?

Answer 18

• Superior optic radiations project through parietal lobe
• Damage here can cause a contralateral inferior homonymous quadrantanopia

Question 19

What are the functions of the temporal lobe?

Answer 19

• Emotion
• Memory
• Hearing
• Olfaction

Question 20

Where is the primary auditory cortex located and what does damage to this area cause?

Answer 20

• Superior surface of temporal lobe, near to Wernicke’s area
• Damage leads to a number of complex effects on hearing e.g. auditory hallucinations

Question 21

Where is the hippocampus located and what does damage to this area cause?

Answer 21

• Crucial structure for consolidating declarative memories located in temporal lobe
• Damage may lead to amnesia
• Some pathologies such as temporal lobe epilepsy can trigger the feeling of deja vu

Question 22

Why is the temporal lobe involved in emotion?

Answer 22

• Temporal lobes contain a number of limbic system structures such as the hippocampus and amygdala

Question 23

What effect do temporal lobe lesions have on emotions?

Answer 23

• Complex effects
• May be related to the pathogenesis of some psychiattric disorders

Question 24

How is the temporal lobe involved in the visual pathway?

Answer 24

• Inferior optic radiations project through the temporal lobe
• Damage here can cause a contralateral superior homonymous quadrantanopia

Question 25

What is meant by cerebral dominance?

Answer 25

- Some functions are represented more prominently in one hemisphere - Knowledge of cerebral dominance allows us to predict the effects of lobe lesions

Question 26

What is the left hemisphere responsible for?

Answer 26

- Dominant for language and mathematical/logical functions - In 95% of people

Question 27

What is the right hemisphere responsible for?

Answer 27

- Dominant for body image, visuospatial awareness, emotion and musical ability - In 95% of people

Question 28

What is the function of the corpus callosum?

Answer 28

- Allows the two hemispheres to communicate with one another - Destruction of corpus callosum can lead to some interesting deficits such as alien hand syndrome and subtle effects on language processing

Question 29

Where is Broca's area found?

Answer 29

- In the infero-lateral frontal lobe - Sits near to the mouth and pharynx area of the primary motor cortex

Question 30

What is the function of Broca's area?

Answer 30

- Responsible for the production of speech

Question 31

What does damage to Broca's area cause?

Answer 31

- Staccato speech - Patient still understands what is being said to them

Question 32

Where is Wernicke's area found?

Answer 32

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

Question 33

What is Wernicke's area responsible for?

Answer 33

- Responsible for the comprehension of speech

Question 34

What does damage to Wernicke's area cause?

Answer 34

- Fluent non-sensical speech where the patient does not appear to understand what is being said to them

Question 35

What can large middle cerebral artery infarcts cause ?

Answer 35

- Dense/global aphasia - Where both areas are destroyed leading to virtually no verbal language function

Question 36

What connects Broca's and Wernicke's areas?

Answer 36

- Arcuate fasciculus

Question 37

What can damage to the arcuate fasciculus cause?

Answer 37

- Inability to repeat heard words

Question 38

What are the different types of memory?

Answer 38

- Declarative/explicit - Non-declarative/implicit - Short term memory - Long term memory

Question 39

What is declarative/explicit memory?

Answer 39

- Factual information - Tends to be stored in cerebral cortex

Question 40

What is non-declarative/implicit memory?

Answer 40

- Motor skills - Emotion - Tends to be stored in subcortical structures (e.g. basal ganglia) and cerebellum

Question 41

What is short term memory?

Answer 41

- Stored for seconds to minutes as a reverberation or echo in cortical circuits

Question 42

What is long term memory?

Answer 42

- Stored for very long periods of time in the cerebral cortex, cerebellum etc. following consolidation

Question 43

What is consolidation?

Answer 43

- Converting short term memories into long term memories

Question 44

What are the factors influencing consolidation?

Answer 44

- Emotional context - Rehearsal - Association

Question 45

What is the function of the hippocampus?

Answer 45

- Sits deep in the temporal lobe (rolled medial edge of the temporal lobe) - Has multimodal inputs from many brain systems, making it good at associating stimuli - Has a role as an oscillator, facilitating consolidation of memories in the cortex via its output pathways

Question 46

What are the output pathways of the hippocampus?

Answer 46

- Fornix - Mamillary bodies - Thalamus - Cortex

Question 47

What is long term potentiation?

Answer 47

- Key molecular mechanism of memory consolidation - Causes changes in glutamate receptors in synapses leading to synaptic strengthening - New physical connections can also form between neurones to further strengthen connections (axonal sprouting)