(neuro) cortical organisation & function Flashcards
what is the cerebral cortex?
layer that is a couple millimetres thick that covers the entire surface of the brain
describe the structural features of the cerebral cortex
contains grey matter (cerebral cortex AND deep grey matter nuclei)
made up of gyri and sulci (highly folded)
lobed
what are fissures?
large sulci that separate the cerebrum into lobes
differentiate between fissures and sulci
sulci are depression in the cerebral cortex
fissures are larger and deeper depressions that separate the cerebrum into lobes
how is the cerebral cortex microscopically organised?
organised into layers and columns
what is Brodmann’s cytoarchitecture?
approx 52 regions of the brain classified depending on cell type, cell packing, cell spacing and cell function etc
name the four lobes of the brain
frontal, parietal, occipital and temporal
what are the main functions of the frontal lobe?
contains primary motor cortex (regulating and initiating motor function)
executive functions (e.g. judgement, reasoning, language, memory, attention etc)
what are the main functions of the parietal lobe?
contains primary somatosensory cortex (regulates sensation = pain, touch)
interoception (self-perception) and spatial orientation
sensory aspects of language
what are the main functions of the occipital lobe?
processing visual information
what are the main functions of the temporal lobe?
processing auditory information
emotions and memory
what are the main functions of the limbic lobe?
responsible for memory, emotion, motivation, reward and learning
what are the main functions of the insular cortex?
visceral sensations
autonomic control
interoception
auditory processing
visual-vestibular integration
where is the insular cortex found?
deep within the lateral fissure
what is the internal structure of the cerebrum made up of?
made up of grey matter and white matter
what is grey matter?
neuronal cell bodies and glial cells
what is white matter?
myelinated neuronal axons arranged in tracts
differentiate between white matter and grey matter
white matter consists of neuronal axons arraned in tracts whereas grey matter is a collection of neuronal cell bodies and glial cells
what is the function of white matter tracts?
connect cortical areas
what are the three types of white matter tracts?
association fibres
comissural fibres
projection fibres
what are the three types of white matter tracts?
association fibres
commissural fibres
projection fibres
what are association fibres?
connect areas within the same hemisphere together
what are commissural fibres?
connect homologous structures in the left and right hemispheres toghether
what are projection fibres?
connect cortex with lower brain structures (e.g. thalamus, brainstem and spinal cord)
e.g. corticospinal tract
besides the brain where else are commissural fibres found?
found in the spinal cord too (connecting homologous right and left structures)
what are the two types of association fibres?
short fibres and long fibres
name four examples of association fibres
superior longitudinal fasciculus
arcuate fasciculus
inferior longitudinal fasciculus
uncinate fasciculus
what does the superior longitudinal fasciculus connect?
the frontal and occipital lobes
what does the inferior longitudinal fasciculus connect?
the temporal and occipital lobes
what does the arcuate fasciculus connect?
the frontal and temporal lobes
what does the uncinate fasciculus connect?
the anterior frontal and temporal lobes
what is a fasciculus?
a bundle of fibres
give two examples of commissural fibres in the brain
corpus callosum
anterior commissure
what lower brain structures will projection fibres connect the cortex to?
thalamus, spinal cord, brain stem etc
what are the two types of projection fibres?
afferent or efferent tracts
differentiate between the afferent and efferent tracts of projection fibres
projection fibres are made up of afferent and efferent fibres
afferent fibres (tracts) travel towards the cortex
whereas efferent fibres (tracts) travel away from the cortex
why do afferent tracts travel towards the cortex?
carry sensory information from various parts of the body to the primary somatosensory cortex in the parietal lobe
why do efferent tracts travel away from the cortex?
carry nerve impulses from the primary motor cortex in the frontal lobe to various parts of the body to bring about movement
give examples of projection fibres
both corona radiat ana dinternal capsule contain afferent and efferent fibres
1) corona radiata = deeper out to cortex
2) internal capsule = (extension of the corona radiata) fibres converge through internal capsule between thalamus and basal ganglia
what is the corona radiata?
bundle of projection fibres that radiate further out to the cortex
(large projection of fibres to larger area)
what is the internal capsule?
bundle of projection fibres that converge separating the thalamus and caudate nucleus from the lentiform nucleus
(large projection of fibres to smaller area)
differentiate between primary cortices and secondary/association cortices
primary cortices have predictable functions, are organised topographically and have right-left symmetry
HOWEVER
secondary cortices have less predictable functions, are not organised topographically and have weak/absent right-left symmetry
name the primary cortices
primary motor cortex
primary somatosensory cortex
primary visual cortex
primary auditory cortex
name the secondary/association cortices
secondary motor cortex
secondary somatosensory cortex
secondary visual cortex
secondary auditory cortex
how can the function of various cortices be worked out?
stimulation during surgery or studying the consequences of lesions to cortex
what are the three motor areas of the frontal lobe?
primary motor cortex
supplementary area
premotor area
what is the function of the primary motor cortex?
controls and enables precise, dextrous voluntary movements by providing descending signals
what is the function of the supplementary area?
involved in planning complex movements (i.e. internally cued)
what is the function of the premotor area?
involved in planning complex movements (i.e. externally cued)
where is the primary motor cortex found?
anterior to the central sulcus
where is the premotor area found?
anterolateral to the primary motor cortex
where is the supplementary area found?
anteromedial to the primary motor cortex
what are the two somatosensory regions in the parietal lobe?
primary somatosensory cortex
somatosensory association
what is the function of the primary somatosensory cortex?
processes somatic sensations (e.g. proprioception, fine touch, pain, vibration, two-point discrimination and temperature)
what is the function of the somatosensory association?
interpreting the significance of sensory information
awareness of self and personal space
where is the primary somatosensory cortex found?
posterior to the central sulcus in the parietal lobe
where is the somatosensory association found?
posterior to the primary somatosensory cortex in the parietal lobe
name the types of somatic sensations that the primary somatosensory cortex is responsible for detecting
vibration pain two-point discrimination fine touch proprioception
what are the two visual regions in the occipital lobe?
primary visual cortex
visual association
what is the function of the primary visual cortex?
processes visual stimuli
what is the function of the visual association?
interprets and provides the meaning of visual input
what are the two auditory regions in the occipital lobe?
primary auditory cortex and auditory association
what is the function of the primary auditory cortex?
processes auditory stimuli
what is the function of the auditory association?
interprets and provides the meaning of auditory input
name three general association areas
prefrontal cortex, Broca’s area and Wernicke’s area
what is the function of the prefrontal cortex?
responsible for executive functions such as attention, adjusting social behaviour, planning, personality expression and decision making
what is the function of the Broca’s area?
speech production
what is the function of the Wernicke’s area?
speech comprehension
how would a lesion of the prefrontal cortex present?
patient undergoes personality and behaviour changes (+ loss of inhibition)
how would a lesion of Broca’s area present?
expressive aphasia - poor production/inability to produce speech but comprehension intact
how would a lesion of Wernicke’s area present?
receptive aphasia - poor comprehension/inability to comprehend speech but production is fine
what is the association cortex for Broca’s area?
Wernicke’s area
how would a frontal lobe lesion present?
loss/change in personality
inappropriate behaviour
how would a parietal lobe lesion present?
contralateral neglect
lack of awareness of self and extrapersonal space on contralateral side
impaired processing and interpretation of somatic sensations
how would a temporal lobe lesion present?
leads to agnosia (inability to recognise and identify objects)
cannot form new memories
(depending on whether lesion is lateral/medial)
what are the two types of lesions to the temporal lobe?
lateral temporal lobe lesion
medial temporal lobe lesion
what is expressive aphasia?
inability/reduced ability to produce speech but comprehension is intact
what is receptive aphasia?
inability/reduced ability to comprehend speech but production is intact
what is expressive aphasia indicative of?
lesion to Broca’s area
what is receptive aphasia indicative of?
lesion to Wernicke’s area
how does a lesion of the primary visual cortex present?
blindness in the corresponding part of the visual field (inability to process/receive visual stimuli)
how does a lesion of the visual association present?
deficits in the interpretation of visual information (i.e. prosopagnosia - inability to recognise familiar faces or learn new faces - face blindness)
define prosopagnosia
inability to recognise familiar faces or learn new faces (face blindness)
what is face blindness?
prosopagnosia - inability to recognise familiar faces and learn new faces
what happens when a primary cortex gets a lesion?
stops receiving information
what happens when a secondary/association cortex gets a lesion?
cannot interpret the meaning of the information being received
how do we assess cortical function using imaging?
either PET scan or a fMRI
what is a PET scan?
measures blood flow directly to a brain region
positron emission tomography
what is a fMRI scan?
measures amount of oxygen in a brain region
functional magnetic resonance imaging
how does a PET scan work?
radioactive molecules attach to glucose
so regions with more glucose = heightened blood flow = increased radioactive signals = more activity here in these regions comparatively
greater uptake of glucose during specific activity
how can cortical function be assessed using encephalography?
encephalography (EEG)
magnetoencephalography (MEG)
how does encephalography work?
measure electrical signals produced by the brain
how does magnetoencephalography work?
measures magnetic signals produces by the brain
what conditions are detected by an EEG?
sleep disturbances, epilepsy
how is encephalography carried out?
numbered electrodes pushed onto scalp to corresponding brain regions and waves mapped out and studied
what is the outcome of elcephalography?
series of waves that reflect the sequential activation of neural structures along the somatosensory pathways
what is transcranial magnetic stimulation (TMS)?
stimulation of neurones using electromagentic induction to assess integrity of neural circuits
what is transcranial direct current stimulatio (tDCS)?
using low direct current to increase or decrease neuronal firing rate
what is diffusion tensor imaging (DTI)?
imaging based on the diffusion of water molecules
what is diffusion tensor imaging (DTI) with tractography?
imaging in the form of 3D reconstruction to assess neural tracts
how can cortical function be assessed using brain stimulation?
TMS (transcranial magnetic stimulation)
tDCS (transcranial direct current stimulation)
how can cortical function be assessed using imaging (assessment of structure)?
DTI (diffuse tensor imaging)
DTI with tractography
what are the four ways cortical function can be assessed?
imaging (PET/ fMRI)
brain stimulation (TMS, tDCS)
encephalography (EEG, MEG)
imaging to assess structure (DTI, +tractography)
what is the function of white matter tracts?
connect cortical regions together
i.e. bundles of myelinated axons
how is the cerebral cortex arranged in columns?
small pyramidal neurone
stellate neurone
large pyramidal neurone
how is the cerebral cortex arranged in layers?
layers I-VI
molecular external granular external pyramidal internal granular internal pyramidal multiform
what are the components of the limbic lobe?
amygdala
hippocampus
mammillary body
cingulate gyrus
which association fibre connects Broca’s and Wernicke’s areas?
arcuate fasciculus
which potential types are used in encephalography to evoke a response?
visual evoked potentials
event-related potentials
somatosensory evoked potentials
