S8 - Higher Cortical Function

Question 1

outline the functions of the frontal lobes

and hence what may be lost if the frontal lobe is damaged

there are 6 key functions

Answer 1

Motor
Frontal lobe damage can result in contralateral motor
weakness

Expression of speech (usually left hemisphere)
Broca’s area is here
Damage to left frontal lobe can result in expressive dysphasia

Behavioural regulation / judgement
Prefrontal cortex etc. is here
Damage to frontal lobes can lead to (usually) impulsive, disinhibited behaviours e.g. sexual
inappropriateness, aggression

Cognition
Prefrontal cortex etc.
Frontal lobe damage (particularly the right) can
cause difficulty with tasks such as complex
problem solving, including calculation

Eye movements
Contain the frontal eye fields
Damage can cause problems with conjugate gaze and other eye movement disturbances

(however, diplopia without other cortical features would suggest brainstem/cranial nerveproblem)

Continence
Contain cortical areas responsible for
maintenance of continence
Damage can cause urinary incontinence

Question 2

outline the parietal lobe functions and what may happen in damage

5 Functions

Answer 2

Parietal lobe functions, with effects of cortical damage

Sensory
Contains primary sensory cortex and associated
areas
Damage might result in contralateral anaesthesia affecting all modalities

Comprehension of speech
Contains part of Wernicke’s area
Damage to left parietal lobe can cause a receptive dysphasia

Body image and awareness of external environment
Seems to be involved with acknowledgement that things (including the body) exist ie not aware of half of your body
Damage to right parietal lobe can lead to neglect.

Calculation and writing
Works with frontal lobe to perform these tasks
Damage to left parietal lobe can affect
calculation ability (but maybe also frontal lobe)

Although not a cortical function, remember that the
superior optic radiation projects through the parietal
lobe
Damage here can cause a contralateral inferior
homonymous quadrantanopia

Question 3

outline temporal lobe functions and what can occur with damage to them

5 Functions

Answer 3

Temporal lobe functions, with effects of cortical damage

Hearing
Primary auditory cortex sits on superior surface
of temporal lobe, near to Wernicke’s area
Auditory hallucinations may be a
feature of temporal lobe lesions

Olfaction
Primary olfactory cortex sits on the inferomedial aspect of the temporal lobe
Olfactory hallucinations may be a featureof temporal lobe lesions

Memory
The hippocampus is a crucial structure for consolidating declarative memories
Damage may lead to amnesia.

Emotion
Temporal lobes contain a number of limbic
system structures such as the hippocampus and amygdala
Effects of lesions are complex, but may be
related to pathogenesis of some psychiatric
disorders

Although not a cortical function, remember that the
inferior optic radiation projects through the temporal
lobe
Damage here can cause a contralateral superior
homonymous quadrantanopia

Question 4

read this info on the cerebral cortex

name 3 types of fibres that are neural outputs and where they travel between

how do we maintain consciousness

what is the general role of interneurones

Answer 4

The cerebral cortex
Fine structure
Arranged as 6 layers containing cell bodies and dendrites (i.e. cortex is grey mater)

Most outputs from the cortex are the axons of
pyramidal neurones
(e.g. upper motor neurones in the primary motor cortex are pyramidal neurones)

Outputs can be projection fibres going down to brainstem and
cord (e.g. upper motor neurones)
Outputs can be commissural fibres going between
hemispheres (e.g. corpus callosum)
Outputs can be association fibres connecting nearby regions of cortex in the same hemisphere (e.g. arcuate fasciculus)

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

Interneurones connect inputs and outputs in a complex way, giving rise to behaviour, emotion, memory etc.

Question 5

outline cerebral dominance

Answer 5

Some functions are represented more prominently in one hemisphere
In 95% of people, the left hemisphere is dominant for language andmathematical/logical functions

In 95% of people the right hemisphere is dominant for body image,visuospatial awareness, emotion and musical ability

The corpus callosum allows the two hemispheres to communicate with one another

info: Destruction of the corpus callosum can cause some interesting deficits such as alien hand syndrome and subtle effects on language
processing

Question 6

what are the two language pathways in the brain, what connects them?

you may want to draw them on a brain
what occurs in damage to them

Answer 6

Broca’s area
In the infero-lateral frontal lobe
Responsible for the production of speech

Damage can cause broca’s / expressive dysphasia where the patient still understands what is being said to them

Wernicke’s area
Sits near to primary auditory cortex in temporal lobe
Responsible for the comprehension of speech
Damage can cause fluent, nonsensical speech where the patient does not appear to understand what is being said to them (Broca’s / receptive dysphasia)

Large middle cerebral artery infarcts can cause am dense / global aphasia where both areas are destroyed leading to virtually no verbal language function

Broca’s and Wernicke’s areas are connected by the arcuate fasciculus
Damage to this white matter pathway can cause the inability to repeat heard words

Question 7

what are the 4 types of memory

Answer 7

Types of memory

 Declarative / explicit
Factual information
Tends to be stored in cerebral cortex

Nondeclarative / implicit
 Motor skills
 Emotion
 Tends to be stored in subcortical structures (e.g. basal ganglia) and cerebellum

Short term memory
 Stored for seconds to minutes as a ‘reverberation’ or ‘echo’ in
cortical circuits

Long term memory
 Stored for very long periods in the cerebral cortex, cerebellum
etc. (up to a lifetime) following consolidation

Question 8

what is consolidation

what factors influence this ?

also outline the role of long term potentiation

Answer 8

Converting short term memories into long term memories

Factors influencing consolidation
o Emotional context (if an event has strong emotional
content, then it tends to be remembered better)
o Rehearsal (you are all familiar with this idea)
o Association (if you can associate a piece of knowledge
with something you already know it tends to be more
easily remembered)

The hippocampus helps to consolidate declarative memories
The hippocampus sits deep in the temporal lobe

Long term potentiation (LTP) is the 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 tofurther strengthen connections (axonal sprouting)