Organisation of the cerebral cortex Flashcards
what percentage of neurones in the grey matter are hidden?
70%
what makes up the central white matter?
myelinated neuronal axons that make the tracts
what are the 6 layers of the neocortex from superficial to deep?
- molecular
- external granular (association fibres)
- external pyramidal (association fibres)
- internal granular (thalamic input)
- internal pyramidal (input)
- multiform (output)
what does the molecular level contain?
layer 1–>neuropil: dense network of interwoven nerve fibres and glia
what do the external granular and external pyramidal layers contain?
small pyramidal neurones and their primary cortico-cortical connections
what does the internal granular layer contain?
layer 4: stellate neurones with local axons in primary sensory cortices receiving input from the thalamus
what do the internal pyramidal and multiform layers contain?
pyramidal neurones whose axons leave the cortex
contain large Betz cells
what are Brodmann’s areas based on?
histology and function
area that responds to the same stimuli
what are association fibres?
connect areas within the same hemisphere
there are short and long fibres connecting structures of varying distance apart
what fibres connect the right and left hemisphere?
commissural fibres
what do projection fibres connect?
cortex to lower brain structures like the thalamus, brain stem and spinal cord
example of commissural fibre?
corpus callosum
example of projection fibre?
internal capsule
what association cortex is found in the occipital lobe?
vision
what are the ventral and dorsal pathways of the VAC responsible for?
ventral- form and colour
dorsal- spatial relationship and movement
what’s the result of injury to the parietal lobe?
examples of spatial mapping problems
disorientation and inability to map or understand spatial relationships
apraxia and neglect
what lobe is responsible for language, object recognition, memory and emotion?
temporal
what is the result of injury to the temporal lobe?
agonsia- inability to interpret sensations
receptive aphasia- inability to comprehend (Wernickes)
what is the function of frontal lobe?
judgement
foresight
personality
appreciation of self in relation to the world
injury to the frontal lobe leads to-
deficits in planning
inappropriate behaviour e.g. hyper sexuality
which regions are responsible for voluntary skeletal muscle movements?
primary motor cortex (precentral gyrus)
premotor cortex (motion association area) Brodmanns 6
what are the primary somatosensory cortex and sensory association area responsible for?
where are they located?
Recognition and interpretation of sensory information from skin, muscles and taste buds
located in the parietal lobe
where are the primary visual cortex and association area located?
in the occipital lobe
where is the primary auditory cortex and association area located?
in the temporal lobe
which area coordinates information with the other association areas?
where is it located?
prefrontal association area
located in the frontal lobe
consequences of lesion of PMC
o Paralysis – full or partial loss of fine voluntary movements contralateral.
o Paresis – muscular weakness
consequence of lesion of pre-motor cortex i.e. the motor association area?
o Apraxia – difficulty in motor planning to perform voluntary tasks
consequences of lesion of the prefrontal association area in the frontal lobe?
o Deficits in planning and inappropriate behaviour.
This area is often involved in personality, self-control, attention, planning, emotions, motivation, decision making and reasoning.
o Aphasia – inability to create speech but preserved comprehension.
- Broca’s area is in the frontal lobe.
consequences of lesion in primary somatosensory cortex?
sensory deficits in perception of basic sensory information
consequences of lesion in sensory association area
o Sensory deficits – in interpretation of sensory information.
E.G. Spatial neglect – unawareness of contralateral side.
Area is involved in – tactile recognition, flavour recognition, spatial orientation, ability to read maps, reading, writing and calculations.
- Alexia – inability to recognise or read words.
- Agraphia – inability to write words.
- Acalculia – inability to perform calculations.
consequence of lesion in primary visual cortex?
in visual association area?
blindness
visual deficits
- interpretation of visual information
- prosopagnosia: inability to recognise familiar faces (ventral pathway)