organisation of the cerebral cortex

Question 1

describe the organisation of the white and grey matter in the brain *

Answer 1

grey matter is a cortical ribbon

white is in the middle - white because of the myelin

Question 2

what are the 3 types of white matter fibre *

Answer 2

association fibres

commissural fibres

projection fibres

Question 3

what is the function of association fibres *

Answer 3

connect areas within the same hemisphere

run between adjacent areas in cortex

coordinate functions in these areas

Question 4

what is the dunction of commissural fibres *

Answer 4

connect L hemisphere to R hemispere

main one is corpus collosum

also ave anterior collosum (limbic function) and posterior collosum

Question 5

what is the function of projection fibres *

Answer 5

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

Question 6

describe the cortical layers of the grey matter *

Answer 6

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

Question 7

describe columnar organisation in the cortex *

Answer 7

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

Question 8

what is the primary cortex in the frontal lobe *

Answer 8

primary motor cortex

anterior to teh central sulcus

Question 9

what is the primary cotex in the parietal lobe *

Answer 9

primary somatosensory cortex

behind the central sulcus

Question 10

what is the primnary cortx in the occipital lobe *

Answer 10

visual cortex

Question 11

what is the primary cortex in the temporal lobe *

Answer 11

teh auditory cortex

in the superior temporal gyrus

Question 12

general features of primary cortices *

Answer 12

functionally predictable

organised topographically

l and r symettry

Question 13

describe the prefrontal association area *

Answer 13

in the frontal lobe

coordiante information from oter association areas

controls behaviour and personality changes

Question 14

describe the motor association area *

Answer 14

involved in motor planning

in the forntal lobe

Question 15

describe the sensory association area *

Answer 15

different sensory modalities map here, close to the primary somatosensory cortex

Question 16

describe the visual association area *

Answer 16

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

Question 17

where are the gustatory and olfactory cortices *

Answer 17

this is less well defined

Question 18

describe association cortices in general comparing them to primary cortices *

Answer 18

their functions are less well defined

not organised topographically (primary are)

L R symettry is weak/absent (primary ave l and r symettry)

Question 19

compare functional methods for testing lesions *

Answer 19

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

Question 20

what is the effect of a lesion in the visual association cortex *

Answer 20

lesions of the visual posterior association area - fulsiform gyrus = inability to learn new faces or recognise familiar ones - this is prospagnosia (face blindness)

Question 21

what is the effect of frontal cortex lesions *

Answer 21

lack of planning, disorganised beaviour

attention span and conc deminish

self control impaired

eg in frontal lobe dementia

Question 22

effect of a parietal lobe lesion *

Answer 22

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

Question 23

example of when you would have parietal cortex lesions

Answer 23

when demetia has progressed here

Question 24

what is the consequence of a temporal cortex lesion *

Answer 24

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

Question 25

describe hemispheric specialisation *

Answer 25

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

Question 26

describe diffusion tensor imaging *

Answer 26

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

Question 27

describe transcranial magnetic stimulation (TMS) *

Answer 27

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

Question 28

describe transcranial direct current stimulation *

Answer 28

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

Question 29

describe positron emission tomography (PET)*

Answer 29

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

Question 30

what is teh difference between magnetoencephalograpy and electroenccepalograpy *

Answer 30

MEG - measure magnetic fields

EEG - measure electric fields

Question 31

describe MEG and EEG *

Answer 31

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

Question 32

describe fMRI *

Answer 32

see the blood flow into the brain - increased flow = increased activity

see if there is an infart or a subtle change

Question 33

how can you measure optimism *

Answer 33

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