8. Higher cortical function Flashcards
what is the anatomy of the cerebral cortex?
arranged as 6 layers containing cell bodies and dendrites
what are the three types of outputs exiting from the cortex?
- projection fibres going down brainstem and cord (upper motor neurone)
- commissural fibres going down hemispjheres (corpus callosum)
- association fibres connecting nearby regions of the cortex in the same hemisphere (arcuate fasciculus)
what are the inputs the cortex receives?
from thalamus or other areas of the cortex as well as from the reticular formation (consciousness)
what connects the inputs and outputs and what function results from this?
interneurones - behaviour, emotion and memory
give examples of motor functions of the frontal lobe?
PMC - damage would result in contralateral weakness
how is speech enabled in the frontal lobe and which hemisphere does this usually originate in?
left hemisphere:
the broca’s area is here so damage can lead to expressive dysphagia
how is behaviour regulated in the frontal lobe?
prefrontal cortex is here whereby if damaged can result in impulsive, disinhibited behaviours - inappropriateness and aggresion
how is cognition enabled in the frontal lobe?
prefrontal cortex so damage can lead to difficulties wiht problem solving and calculations
how are eye movements enabled in the frontal lobe?
contain the frontal eye fields so dmaage can lead to conjugate gaze and other disturbances
how do you differenitate between diplopia causes by a cranial nerve/brainstem lesion versus a cortical problem?
diplopia without other cortical features would suggest problem originates with cranial nerve/brainstem
how is continence enabled in the frontal lobe?
contain the cortical areas (paracentral lobules) responsible, so damage can result in urinary continence
how is the sensory function of the parietal lobeenabled?
contain the PSC - if damage, contralteral parasthesia affecting all modalities (as modalities converge at the cortex)
why is the parietal lobe responsible for speech?
contains part of the Wernicke’s area so damage to the left lobe esp can cause receptive dysphagia
why is the parietal lobe responsible for body image and awareness of the external environment?
where acknowledgment of things including the body exists. if damage in right lobe - neglect
why is the parietal lobe responsible for calculation and writing and which lobe does it work with?
esp left parietal - work with frontal
what kind of vision can be affected by parietal lobe lesions?
as the superior optic radiations project through the parietal lobe, damage can cause a contralateral inferior homonymous quadrantanopia
why is the temporal lobe responsible for hearing?
the primary auditory cortex sits on superior surface of temporal lobe, near to wernicke’s area, if damaged can lead to auditory hallucinations
how is olfaction of the temporal lobe enabled?
the primary olfactory cortex sits on the infero-medial aspect so can lead to olfactory hallucinations if damaged
how is memory enbaled within the temporal lobe?
the hippocampus(one in each lobe) is present so if damage can lead to amnesia or if epilepsy within the temporal lobe can lead to feeling of deja vu
why is the temporal lobe responsible for emotion?
contains limbic system structures such as hippocampus and amygdala, can result in some pschiatric disorders if damaged
what kind of vision loss can result from a temporal lobe lesion?
the inferior optic radiations project through temporal lobe so damage can lead to a contralateral superior homonymous quadrantanopia
in 95% of people the left hemisphere is dominant for what?
language and mathematical/logical function
in 95% of people the right hemisphere is dominant for what?
body image, visuospatial awareness, emotion and musical ability
what can damage to the corpus callosum result in>
corpus callosum allows communication with the two hemispheres so destruction can lead to alien hand sydrome and effects on language processing (comple)
why is the position of the broca’s area so convienient>
sits near mouth/pharynx area of PMC
what can result from ddmage to the broca’s are?
stacatto speech where patient understands what is being said to them but can not express their response
why is the position of the wernicke’s area so convenient?
sits near the primary auditory cortex
what can result from damage to the wernicke’s area?
fluent, non sensical speech where patient does not appear to understand what is being said to them but has no trouble in speech expressio
what damage can result in both the broca and wernicke’s area?
middle cerebral artery infarcts - resulting in no verbal language function
what area is damaged when the individual can not repeal heard words?
the arcuate fasciculus (white matter pathway connecting broca and wernicke’s areas)
what are the 4 types of memory?
- declarative/explicit - tend to be stored in cortex
- non declarative/implicit - motor skills, emotion in subcortical structure such as basal ganglia and cerebellum
- short term memory - in cortical circuits
- long term memory - in cortex and cerebellum following consolidation
what is consolidation?
the convertion of short term memories to long term memories
what are the factors influencing consolidation?
- emotional context
- rehearsal
- association with something already known
how is the hippocampus involved in memory?
role as an ‘oscillator’
its output pathways facilitate consolidation
fornix -> mammillary bodies -> thalamus -> cortex
what molecular mechanism is important in consolidation?
long term potentiation - changaes in gluatamate receptors in synpases leading to synapse strengthening, and new physical connections can form between neurones leading to further stronf connections
