Cerebral cortex Flashcards
Describe the grey and white matter in the brain
Grey outside, white inside
Describe the types of cerebral white matter
Association fibres: connect areas within the same hemisphere
Commissural fibres: connect left hemisphere to right hemisphere
Projection fibres: connect cortex with lower brain structures (e.g. thalamus), brain stem and spinal cord
Describe the cortical layers of the grey matter
1-3 - cortico-cortical connections
4 - thalamus
5+6 - subcortical, brainstem, spinal cord
Neocortex is arranged in layers (lamina structure) and columns
More dense vertical connections – basis for topographical organization
Neurons with similar properties are connected in the same column
Describe the function of the occipital lobe
Visual cortex + Visual association area = vision
visual association cortex analyses different attributes of visual image in different places
form and colour analyzed along ventral pathway; spatial relationships and movement along dorsal pathway
Describe the parietal lobe
Primary somatosensory cortex + Sensory association area = Sensory information from skin, musculoskeletal system, viscera and taste buds
posterior parietal association cortex creates spatial map of body in surroundings, from multi-modality information
Describe the frontal lobe
judgement, foresight, personality, appreciation of self in relation to world
Frontal lobe + prefrontal association area = coordinates into from other association areas, controls some behaviours
Primary motor cortex + motor association area = Skeletal muscle movement
Gustatory cortex = taste
Describe the temporal lobe and what a lesion would affect/cause
language, object recognition, memory, emotion
Auditory cortex + Auditory association area = hearing
Olfactory cortex = smell
injury leads to agnosia, receptive aphasia
Describe the primary cortices of the grey matter
function predictable organised topographically left-right symmetry
Primary motor cortex Primary somatic sensory cortex Visual cortex Auditory cortex Gustatory cortex Olfactory cortex
Describe the association cortices of the grey matter
function less predictable not organised topographically left-right symmetry weak or absent Prefrontal association area Motor association area Sensory association area Visual association area Auditory association area
What are the functions of the primary and association cortices combined
frontal - coordinates information from other association areas, controls some behaviour
Motor - skeletal muscle movement
Somatic sensory - sensory info formskin musculoskeletal system, viscera, taste buds
Visual - vision
Auditory - hearing
What can a lesion of the visual association Cortex lead to
Lesions of the visual posterior association area (fusiform gyrus) can result in the inability to recognize familiar faces or learn new faces—a deficit called prosopagnosia (aka face blindness).
What can a lesion of the frontal cortex lead to
Lack of planning
Behaviour becomes disorganised
Attention span and concentration diminish
Self-control is hugely impaired
What can a lesion of the parietal cortex lead to
disorientation
inability to read maps or understand spatial relationships
apraxia
hemispatial neglect
Describe hemispheric specialisation
Left - language dominant
Right - largely spatial processing
Patients who had a callosotomy (split brain) - lateralised deficits in function
Right - drawing, music, spatial perception
Left - writing, ears, calculation
What is diffusion tensor imaging
Used to measure the effect of lesions in white matter, or brain areas have been disconnected
What is transcranial magnetic stimualtion
The magnetic field induces an electric current in the cortex, causing neurons to fire.
This can be used to test whether a specific brain area is responsible for a function, e.g. speech
What is transcranial direct current stimulation
Changes the local excitability of neurons, increasing or decreasing the firing rate
(NB, does not directly induce neuronal firing)
Could be used to reduce motion sickness
Describe the PET scan
Positron emission tomography
Locates where a particular molecule (e.g. dopamine) is absorbed in the brain
Followed by administration of 18F-FDOPA
What is a MEG and EEG
Magnetoencephalography(MEG) -functional neuroimagingtechnique for mapping brain activity
Electroencephalography (EEG) -electrophysiological monitoring method to record electrical activity of the brain. EEG measures voltage fluctuations resulting from ionic current within the neurons of the brain
Describe the measurements taken with MEG and EEG
Event-related potential / evoked-potentials
EEG and MEG are noisy signals.
Participants perform large numbers of trials so that an average can be used
Describe the fMRI
Measures brain activity by detecting changes associated with blood blow
Relies on cerebral blood flow and neuronal activation being coupled
What are the layers of the grey matter
Dorsal -> ventral
Layers 1-3 = cortico-cortical connections
Layer 4 = input from thalamus
Layer 5-6 = connections with subcortical, brain stem and spinal cord
What is the effect of a visual association cortex lesion
lesions affect specific aspects of visual perception
What is the effect of a temporal lobe lesion
injury leads to agnosia, receptive aphasia
