organisation of the cerebral cortex Flashcards
describe the organisation of the white and grey matter in the brain *
grey matter is a cortical ribbon
white is in the middle - white because of the myelin
what are the 3 types of white matter fibre *
association fibres
commissural fibres
projection fibres
what is the function of association fibres *
connect areas within the same hemisphere
run between adjacent areas in cortex
coordinate functions in these areas
what is the dunction of commissural fibres *
connect L hemisphere to R hemispere
main one is corpus collosum
also ave anterior collosum (limbic function) and posterior collosum
what is the function of projection fibres *
connect cortex with lower brain structures eg thal, brain stem and spinal chord
eg cortical spinal tract - from promary motor cortex to a neurons without synapsing
describe the cortical layers of the grey matter *
6 layers - variation throighout the cortex - motor thicker than somatosensory - has the big betz cells
layer 1 (outside edge of brain) - few neurons, just glial cells - connective fibres (association fibres)
layers 2 and 3 - association fibres - cortico-cortical connections
4 - input recieved here
5 and 6 - output - Betz cells - larger interneurons, they are upper motor neurons and go to brainstem and spinal chord
describe columnar organisation in the cortex *
dense vertical connections - form the basis for topographical organisation - neurons with similar properties are connected in same column - functionally connected
this is columnar functional localisation
what is the primary cortex in the frontal lobe *
primary motor cortex
anterior to teh central sulcus
what is the primary cotex in the parietal lobe *
primary somatosensory cortex
behind the central sulcus
what is the primnary cortx in the occipital lobe *
visual cortex
what is the primary cortex in the temporal lobe *
teh auditory cortex
in the superior temporal gyrus
general features of primary cortices *
functionally predictable
organised topographically
l and r symettry
describe the prefrontal association area *
in the frontal lobe
coordiante information from oter association areas
controls behaviour and personality changes
describe the motor association area *
involved in motor planning
in the forntal lobe
describe the sensory association area *
different sensory modalities map here, close to the primary somatosensory cortex
describe the visual association area *
pick up different aspects of vission
movement and colour
in occipital lobe
dorsal stream is involved in localisation in space - this is the where pathway
ventral stream is involved in visual identification - wat pathway
image attributes are processed separately in association pathways
inputs go into primary cortex
where are the gustatory and olfactory cortices *
this is less well defined
describe association cortices in general comparing them to primary cortices *
their functions are less well defined
not organised topographically (primary are)
L R symettry is weak/absent (primary ave l and r symettry)
compare functional methods for testing lesions *
MEG and ERP - used to assess at macroscopic level - noninvasive
SPECT and PET - involve ligands binding in the brain - more invasive
extracellular single unit recording and intracellular patch - used experimentally - non-invasive and used for seeing small things
what is the effect of a lesion in the visual association cortex *
lesions of the visual posterior association area - fulsiform gyrus = inability to learn new faces or recognise familiar ones - this is prospagnosia (face blindness)
what is the effect of frontal cortex lesions *
lack of planning, disorganised beaviour
attention span and conc deminish
self control impaired
eg in frontal lobe dementia
effect of a parietal lobe lesion *
posterior parietal association cortex males spatial map of body in surroundings from multi-modal information
therefore injury cause disorientation, inability to read maps or understand spatial relationships
get apraxia - difficulty interacting with environment in motor
hemispatial neglect - half the world is non-existant to them
example of when you would have parietal cortex lesions
when demetia has progressed here
what is the consequence of a temporal cortex lesion *
loss of language, object recognition, memory (hippocampus),
agnosia - loss of recognition
receptive aphasia - failure to understand the outside world
anterograde amnesia - cant make any new memories
