cerebral cortex

Question 1

study techniques

Answer 1

staining - nissl staining, lesion studies - on animals lesion parts of cortex see the effects; in humans examine behaviour after pathology surgery or accidents, electrophysiology - EEG, single or multiple neuronal recordings, optogenetics - excite or inhibit specific groups of neurones, imaging - non functional (CT, MRI) and functional imaging (PET, fMRI)

Question 2

cytoarchitecture

Answer 2

neocortex - 6 layers (most of cortex this type) hippocampus 4 layers, broadmann areas are histological analysis of cortex based on laminar distribution, areas that receive sensory input have a wide lamina IV, areas that send out motor outputs have a wide lamina V

Question 3

broadmann areas

Answer 3

50 subdivisions of cerebral cortex, somatosensory sensation - areas 1,23, (post central gyrus), fine motor control - area 4 primary motor cortex (pre central gyrus, conscious visual sensation - area 17, 18 visual cortex, auditory sensation - area 41, 42 auditory cortex, speech production - area 44, 45 broca’s area

Question 4

cerebral cortex neurones

Answer 4

cell bodies of cortical neurones arranges in layers - columnar organisation, layer 1 - few cells, layers 2 and 3 - small pyramidal cells (project to other cortical areas, layer 4 - stellate cells (receive from thalamus), layer 5 - large pyramidal cells (output cells), layer 6 - pyramidal cells (project to thalamus)

Question 5

electroencephalography

Answer 5

measures electrical activity of large groups of neurones in cortex, frequency of activity differs according to behavioural state, can see differences in epilepsy, coma, sleep (delta waves - <4Hz deep sleep, theta waves - 4/7 Hz sleep, alpha waves - 8/13 Hz relaxed wakefulness, beta waves - 13/30 Hz mental activity)

Question 6

single or multiunit neuronal recordings

Answer 6

tungsten micro electrode or multiunit array is placed into cortex to record electrical activity from single neurones (can be more than one act a time)

Question 7

in vivo calcium imaging

Answer 7

enables many cells to be studies in response to a specific stimuli such as a novel smell

Question 8

optogenetics

Answer 8

light used to activate or inhibit specific regions

Question 9

structural imaging - MRI

Answer 9

detects structural changes in living brain - tumours, brain shrinkage, swelling, non invasive, strong magnetic field and radio waves produce images based on hydrogen content (water) of body tissue, no radiation, good images

Question 10

functional imaging - PET & fMRI

Answer 10

positron emission tomography and functional magnetic resonance imaging, detects changes in brain metabolism and blood flow, active neurones need more glucose/oxygen blood vessels respond by increasing blood flow to active regions, shows patterns of activity in intact brain, superimpose PET images onto MRI scan

Question 11

cerebral cortex

Answer 11

seat of consciousness and higher brain functions, layer of grey matter covers entire cerebrum (~ 1.5 -2 m^2), very large ~ 10^10 neurones

Question 12

connections between hemispheres

Answer 12

corpus coliseum, anterior commissure

Question 13

roles of different regions

Answer 13

primary sensory/motor cortices occupy a small fraction of total cortex, remainder (75%) is association cortex - frontal, temporal, parietal and occipital association areas, function - integrate information received from other brain areas and plan appropriate response, inputs - main input from cortico-cortical connects also sensory and motor cortices and other association areas in both hemispheres, thalamus and brainstem, outputs - hippocampus, basal ganglia/ cerebellum, thalamus and other association cortices

Question 14

general connects of cortical areas

Answer 14

primary sensory areas > higher order sensory areas > association areas > premotor areas > primary motor areas

Question 15

parietal association cortex and attention

Answer 15

lesions lead to attention ion deficits - contralateral neglect syndrome, inability to perceive and attend to objects or even own body in certain parts of space, patients deny the existence of the side of the body opposite the lesion nor do they respond to stimuli presented to opposite side of lesion

Question 16

temporal association cortex and recognition

Answer 16

recognition of objects and memory, lesions lead to deficits of recognition, optogenetic silencing of the temporal cortex reduces face recognition, prosopagnosia (face blindness) caused by lesion to lobe, oxytocin may increase face recognition in autism spectrum disorder

Question 17

frontal association cortex and planning

Answer 17

if prefrontal cortex (area anterior to motor cortex) is lesioned can’t perform task, prefrontal cortex contains planning or delay-specific neurones, PET scans reveal activation of dorsolateral frontal cortex during a planning task

Question 18

lateralisation of speech

Answer 18

left hemisphere (most people) - hemispheric lateralisation, damage to these areas causes aphasia - reduced ability. to produce or comprehend language, Broca’s area - frontal association cortex, lesions affect ability to produce language efficiently, wernicke’s area - temporal association cortex damage results in speech that is fluent but makes little sense

Question 19

bilingualism

Answer 19

areas used for processing speech/ language not necessarily same in bilinguals and monolinguals, early bilingual = speech areas overlap for both languages, both strongly lateralised, late bilingual = speech areas non overlapping and much less lateralisation