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
describe hemispheric specialisation *
lateralisation of some function - can live without a corpus collosum
l brain dominant for verbal processing
r brain dominant for pictures
if loss of corpus collosum and see word eg face in L field of vision - go into R brain - vcant communicate with l - can draw word but not say what it is. if see in r field of vision - go into l brain - can say what it is
describe diffusion tensor imaging *
it is a form of MRI - used when subtle changes to function and structure
used to see interruption to topography and look at integrity of funtcional pathway
describe transcranial magnetic stimulation (TMS) *
stimulate the damaged pathway get an understanding of the electrical control
test whether specific brain area is responsible for function
used in therapeutic rehabiulitation of sspinal chord injury
describe transcranial direct current stimulation *
changes the local excitabilty of teh neurons - increases or decreases the firing rate but doesnt induce neuronal firing
it is used to change the sensitivity to your own input
can be used to overcome motion sickness - by suppressing area of cortex associated with processing vestibular information
describe positron emission tomography (PET)*
put ligand in pt and look for its binding
eg look for uptake in dopamine - should be a igh signal in the basal ganglia wich initiates movement - absent in parkinson’s patients
SPECT is usually used
what is teh difference between magnetoencephalograpy and electroenccepalograpy *
MEG - measure magnetic fields
EEG - measure electric fields
describe MEG and EEG *
pt shown reversing checkboards to measure sensitivity of visual cortex
noisy signals so lots of trials have to be done so you can see an average
describe fMRI *
see the blood flow into the brain - increased flow = increased activity
see if there is an infart or a subtle change
how can you measure optimism *
using fMRI
get pt to ting of positive and -ve future
when =ve amygdala and rostral anterior cingulate cortex were more active than when tey imagined -ve events
