Cortical organisation and function Flashcards
where is the cerebral cortex?
covers entire surface of the brain
contains grey matter
what do fissures separate?
hemispheres and lobes
what are Brodmann maps
52 regions based cytoarchitecture (cell size, spacing, packing density and layers)
how are Brodmann maps useful?
areas relate to function e.g primary somatosensory (1,2,3), primary motor (4)
what are the different cerebral cortex lobes
Frontal
Parietal
Temporal
Occipital
what are the functions of the Frontal lobe iM CALM
initiating Motor function Cognitive executive function Attention Language Memory
what are the functions of the parietal lobe?
sensation - touch/pain
sensory aspects of language
spatial orientation and self-perception
what are the functions of the occipital lobe?
processing visual information
gives meaning to images
what are the functions of the temporal lobe
processing auditory information
emotions
memories
what is contained in the limbic lobe?
amygdala, hippocampus, mamillary body, cingulate gyrus
what are the functions of the limbic lobe? MEMs and LeaRning
MEMs and LeaRning memory emotion motivation learning reward
where is the insular lobe?
lies deep into lateral fissure
what is grey matter?
neuronal cell bodies and glial cells
what is white matter?
myelinated neuronal axons
what are the types of white matter tracts?
association fibres, commissural fibres, projection fibres
what are association fibres?
connect areas in same hemisphere
what are commissural fibres?
connect homologous structures in left and right hemispheres
e.g corpus callosum, anterior commissure
what are projection fibres
connect cortex to lower brain structures
what association fibres connect the frontal and occipital lobe?
superior longitudinal fasciculus
what association fibres connnect the frontal and temporal lobes, specifically Brocas and Wernickes area?
arcuate fasciculus
what association fibres connect the temporal and occipital lobes?
Inferior longitudinal fasciculus
what association fibres connect the frontal and temporal lobes?
Uncinate fasciculus
where do commissural fibres pass through
corpus callosum
where do projection fibres converge?
through the internal capsule (between the thalamus and basal ganglia)
how predictable is function from primary cortices?
easily predictable with left-right symmetry
how predictable is function of secondary/association cortices?
less predictable
left-right symmetry is weak or absent
what are the motor areas of the frontal lobe?
primary
supplementary
premotor
what does the primary motor area of the frontal lobe control?
fine, discrete voluntary movements
what does the supplementary motor area of the frontal lobe control?
planning complex movements, internally cued
what does the premotor area of the frontal lobe control?
planning movements, externally cued
what area of the frontal lobe controls fine, discrete voluntary movements?
primary motor area
what area of the frontal lobe plans complex, internally cued movements?
supplementary motor area
what area of the frontal lobe plans movements that are externally cued?
premotor area
what areas are contained in the parietal lobe?
primary somatosensory area
somatosensory association area
what is controlled by the primary somatosensory area?
processes somatic sensations arising from receptors in the body
what is controlled by the somatosensory association area of the parietal lobe?
interpret the significance of sensory information
awareness of self and personal space
what is controlled by the primary visual area of the occipital lobe?
processes visual stimuli
what is controlled by the visual association area of the occipital lobe?
gives meaning and interpretation of visual input
what is controlled by the primary auditory area of the temporal lobe?
processes auditory stimuli
what is controlled by the auditory association area of the temporal lobe?
gives meaning and interpretation of auditory input
what is the prefrontal cortex responsible for? APPSD
attention planning personality expression social behaviour decision making
what is the brocas area responsible for?
motor aspect of speech, production of language
where is the Brocas area?
left frontal lobe, just above sylvian fissure
what is Wernicke’s area responsible for?
understanding and comprehension of language
where is Wernicke’s area found?
left temporal lobe, superiorly and caudally
what is the result of a frontal lobe lesion?
changes in personality, inappropriate behaviour
what is the result of a parietal lobe lesion?
contralateral neglect
lack of awareness of self on opposite side
lack of awareness of opposite side of extrapersonal space
what is the result of a temporal lesion?
agnosia (inability to recognise)
possible anterograde amnesia
what is Brocas aphasia?
expressive aphasia - poor production of speech, comprehension intact
what is Wernicke’s aphasia?
receptive aphasia - poor comprehension of language
what would a lesion to the primary visual cortex of the occipital lobe cause?
blindness in the corresponding part of the visual field
what would a lesion to the visual association area of the occipital lobe cause?
deficits in interpretation of visual information e.g prosopagnosia
what are the 4 main methods of assessing cortical function?
Positron emission tomography (PET)
functional magnetic resonance imaging (fMRI)
electroencephalography (EEG)
magnetoencephalography (MEG)
what is a PET scan?
demonstrates the blood flow directly to a brain region
what is an fMRI scan?
basically a PET using radioactive isotopes of glucose
demonstrates amount of blood oxygen in brain regions
what is an EEG?
measures electrical signals produced by the brain
what is an MEG?
measures magnetic signals produced by the brsin
what are visual evoked potentials?
type of encephalography
stimulates visual sensations
what are somatosensory evoked potentials?
series of waves that reflect sequential activation of neural structures along the somatosensory pathways
what is transcranial magnetic stimulation?
assesses functional integrity of neural circuits, using electromagnetic induction to stimulate neurones
what is transcranial direct current stimulation
uses low direct current over the scalp to increase or decrease neuronal firing rates
what is diffusion tensor imaging?
scan based on the diffusion of water molecules
what is diffusion tensor imaging with tractography?
3D reconstruction of brain to assess neural tracts
Mnemonic for insular lobe?
Insurance AVIVA Auditory processing Visual vestibular integration Interoception Visceral sensation Autonomic control
How to tell brocas and wernickes aphasia apart
Broca C D Expressive aphasia
Wernickes V U T S Receptive aphasia
what is multiple sclerosis?
demyelination of neurones due to autoimmune attack of oligodendrocytes (CNS)
characterised by 2 different areas affected with episodic neurological dysfunction
symptoms of MS?
fatigue difficulty walking blurred vision bladder control issues numbness/tingling stiffness/spasms balance/coord issues cognitive issues
what is the inflammation process of MS?
driven by perivascular and leptomeningeal (arachnoid and pia mater) immune cell infiltration (CD3 T cells, CD20 B cells)
inflammation - demyelination - axonal loss - neurodegeneration
risk factors for MS
family history female other autoimmune vit D deficiency as a child epstein-barr virus smoking
types of MS
relapsing-remitting
primary progressive
secondary progressive - may also have relapse/remiss and faster progression than primary
progressive-relapsing - progressive worsening and acute relapses with no remission
MS early symptoms
ocular pain, blurred vision (optic neuritis)
path of projection fibres?
corona radiata
to internal capsule
into descending white matter tracts (brainstem/spinal cord)
types of association fibres
short fibres - U fibres - connect adjacent gyri within same hemisphere
long fibres - connect distal regions within same hemisphere
what is an M-wave
fast twitch
motor activation - orthrodromic (towards muscle)
electrical stimulus - activates motor axons orthodromically - action potentials - muscle contraction
what is an H-reflex
slow twitch - orthrodromic sensory activation
electrical stimulus - activates sensory axons orthodromically - action potentials to spinal cords - lower motor neurons - muscle contraction
what is an F-wave
slowest muscle twitch
antidromic motor activation (goes backwards through spinal cord - opposite of normal motor M wave)
large electrical stimulus only - activates motor axons antidromically - action potentials to spinal cord - backfire to lower motor neurons - muscle contraction
what do CNS demyelinations show on an EMG
slowed motor neuron latency in CNS so prolonged CMCT (central motor conduction time)
calculation for peripheral motor conduction time (PMCT)
(M latency + F latency-1) /2
-1 is for turnaround time in spinal cord of F wave
how do we measure motor evoked potential latency (total motor conduction time)
transcranial magnetic stimulation (TMS)
measured with an EMG to see how long it takes from activation of motor cortex to muscle contraction
what is total motor conduction time (TMCT)
time taken from stimulation of primary motor cortex by TMS to the contraction of muscle (measured by EMG)
what is peripheral motor conduction time measuring
time from spinal cord to muscle along motor axon
how to calculate central motor conduction time
TMCT - PMCT
how do we know if there is an issue of conduction of CNS neurons? (MS)
longer MEP - could be upper MN, lower MN, both (longer TMCT)
peripheral nerve stim - normal F wave (so normal PMCT) indicates no issue with lower MN
AKA total motor conduction time delayed with normal peripheral motor conduction time