Higher cortical function Flashcards
What is the fine structure of the cerebral cortex?
- Arranged as 6 layers containing cell bodies and dendrites
What are most outputs of the cortex?
- Axons of pyramidal neurones
- E.g. upper motor neurones in the primary motor cortex
Give some examples of outputs of the cortex?
- 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
Where do most inputs to the cortex come from?
- Thalamus and other cortical areas
- An important population of inputs arise from the reticular formation, maintaining cortical activation (consciousness)
What is the function of interneurones?
- Connect inputs and outputs in a complex way
- Gives rise to behaviour, emotion, memory etc.
What are the frontal lobe functions?
- 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)
What happens when the frontal lobe is damaged?
Impulsive and disinhibited behaviours
- Difficulty with tasks such as complex problem solving and calculations
- Problems with conjugate eye movement
Where is the primary motor cortex located and what can damage to this area cause?
- Frontal lobe
- Contralateral motor weakness
Where is Broca’s area located and what can damage to this area cause?
- Damage to left frontal lobe can result in expressive dysphagia
Where is the prefrontal cortex located and what can damage to this area cause?
- Frontal lobe
- Impulsive, disinhibited behaviours e.g. sexual inappropriateness and aggression
- Difficulty with tasks such as complex problem solving, including calculation
Where are the frontal eye fields located and what can damage to this area cause?
- Frontal lobe
- Problems with conjugate gaze and other eye movement disturbances (diplopia without other cortical features suggests brainstem/cranial nerve problem)
Where are the paracentral lobules located and what can damage to this area cause?
- Frontal lobe
- Urinary incontinence
What are the functions if the parietal lobe?
- Sensory
- Comprehension of speech
- Body image and awareness of external environment
- Calculation and writing
Where is the primary sensory cortex located and what can damage to this area cause?
- Parietal lobe
- Contralateral anaesthesia affecting all modalities
Where is Wernicke’s area located and what can damage to this area cause?
- Left parietal lobe
- Receptive dysphasia
Why does damage to the parietal lobe cause neglect?
- Parietal lobe is involved in acknowledgement that things (including the body) exist
- Involved in body image
How does the parietal lobe contribute to calculation and writing?
- Works with frontal lobe to perform these tasks
- Damage to left parietal lobe can affect calculation ability
How is the parietal lobe involved in the visual pathways?
- Superior optic radiations project through parietal lobe
- Damage here can cause a contralateral inferior homonymous quadrantanopia
What are the functions of the temporal lobe?
- Emotion
- Memory
- Hearing
- Olfaction
Where is the primary auditory cortex located and what does damage to this area cause?
- Superior surface of temporal lobe, near to Wernicke’s area
- Damage leads to a number of complex effects on hearing e.g. auditory hallucinations
Where is the hippocampus located and what does damage to this area cause?
- 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
Why is the temporal lobe involved in emotion?
- Temporal lobes contain a number of limbic system structures such as the hippocampus and amygdala
What effect do temporal lobe lesions have on emotions?
- Complex effects
- May be related to the pathogenesis of some psychiattric disorders
How is the temporal lobe involved in the visual pathway?
- Inferior optic radiations project through the temporal lobe
- Damage here can cause a contralateral superior homonymous quadrantanopia
