9 - Higher Cortical Function

Question 1

What are the inputs and outputs to the cortex?

Answer 1

• Cerebral cortex made up of 6 layers

- Input: thalamus and other cortical areas e.g reticular formation

- Output: pyramidal cells and project to wide cell areas (projection fibres via UMNs, commisural fibres via corpus callosum, association fibres like arcuate fasiculus)

- Interneurones connect inputs and outputs

Question 2

What is the function of the frontal lobes?

Answer 2

- Motor cortex

- Expression of speech (left hemisphere - Broca)

- Behavioural regulation (prefrontal cortex)

- Cognition

- Eye movements (frontal eye fields)

- Urinary Continence (paracentral lobules)

Question 3

What are some features that a person may display with a frontal lobe lesion?

Answer 3

- Contralateral weakness

- Expressive/Broca’s dysphasia (left hemisphere)

- Impulsive disinhibited behaviour e.g aggressive, sexually inappropriate

- Difficult with complex problem solving (right hemisphere)

• Conjugate gaze issues/diplopia with other cortical features show frontal lobe lesion not nuclei/brainstem lesion

- Urinary incontinence

Question 4

What is the function of the parietal lobes?

Answer 4

- Sensory cortex

- Understanding speech (left hemisphere - Wernicke’s)

- Body image (right hemisphere)

- Awareness of external environment

- Calculation and writing

- Superior optic radiation runs through here

Question 5

What are some features that a person may have if they had a parietal lobe lesion?

Answer 5

- Contralateral anaesthesia in all modalities (convergence at cortex)

• Receptive Dysphasia/Wernicke’s Aphasia (left)

- Poor calculation ability

- Contralateral inferior homonymous quadrantanopia

Question 6

What lobes are disinhibited when drinking alcohol?

Answer 6

• Frontal
• Cerebellum

Question 7

What is the function of the temporal lobes?

Answer 7

- Hearing (primary auditory cortex on superior surface near Wernicke’s)

- Olfactory (primary olfactory cortex on infero-medial temporal lobe)

- Memory (hippocampus for declarative memories)

- Emotion (limbic system like hippocampus and amygdala)

- Inferior optic radiation

Question 8

What are some features that a person may display if they have a temporal lobe lesion?

Answer 8

- Hearing effects like auditory hallucinations

- Changes in smell like olfactory hallucinations

- Amnesia

- Temporal lobe epilepsy (retriggering memories so like deja vu)

- Psychiatric disorders

- Contralateral superior homonymous quadrantanopia

Question 9

What is the theory of cerebral dominance?

Answer 9

- A person does not depend equally on both hemispheres for a function e.g speech

- Right hemisphere tends to both halves of space but left only attends to right half of space (neglect - man and house on fire)

• Corpus callosum allows two hemispheres to communicate so we are the average of both

Question 10

What is Alien Hand Syndrome?

Answer 10

- Destruction of the corpus callosum (supplies by ACA) so the two hemispheres cannot connect so one hand doesn’t know what the other is doing

• Destruction can also cause language issues

Question 11

If a patient draws this what is the issue?

Answer 11

Left neglect due to damage with right hemisphere, often after a stroke

Question 12

What is the language pathway in the brain?

Answer 12

- Left hemisphere

- Wernicke’s understands speech in parieto-temporal area near auditory cortex. Fluent receptive dysphasia if damaged

- Broca’s produces speech in inferolateral frontal lobe near mouth/pharynx motor area. Staccato speech/expressive dysphasia if damaged

• Joined by arcuate fasiculus and then Broca’s projects to motor cortex

Question 13

What is the input and output to the language pathway in the following scenarios:

• Repeating a heard word
• Speaking a written word
• Speaking a thought

Answer 13

• All outputs from Broca to motor cortex

- Input: primary auditory cortex

- Input: primary visual cortex

- Input: all of cortex

Question 14

What is Wernicke’s and Broca’s aphasia?

Answer 14

Question 15

What can be the language issue if someone has a lesion to their arcuate fasiculus?

Answer 15

Inability to repeat a word said to them

Question 16

What is the blood supply to the language pathway in the brain?

Answer 16

• MCA so large stroke/infarct here can cause global aphasia so no verbal language at all

Question 17

What are the two different classifications of memory and where are they both storeds?

Answer 17

- Declarative: factual information and is stored in cerebral cortex

- Non-declarative: motor skills and emotions and tend to be stored in subcortical areas (basal ganglia) and cerebellum. Starts in basal ganglia and moves to cerebellum the more you consolidate

Question 18

How are long and short term memories stored and what can help with consolidation of memories (conversion from short to long term)?

Answer 18

• Short term memory stored for seconds to minutes as an ‘echo’ in cortical circuits
• Long term stored for very long periods in cerebral cortex, cerebellum following consolidation

Question 19

Which part of the brain helps to consolidate declarative memories?

Answer 19

- Hippocampus (deep temporal lobe)

• Multimodal inputs from many brain systems (making it

good at associating stimuli e.g perfume and dying)

• Role as an ‘oscillator’, facilitating consolidation of

memories in the cortex via its output pathways (primarily the

fornix–> mammillary bodies – >thalamus –> cortex)

Question 20

What is the cellular mechanism of consolidation of memory?

Answer 20

Long term potentiation

• Changes in glutamate receptors leads to synaptic strengthening
• New physical connections can form between neurones to further strengthen connections (axonal sprouting)

Question 21

What are the features of motor neurone disease?

Answer 21

Has a mixture of upper and lower motor neurone signs

Question 22

How does MS typically present?

Answer 22

Progressive relapsing disease common in young women aged 20-40