LOCALISATION OF CORTICAL FUNCTION Flashcards
What are Cytoarchitectural studies?
: mapping out the functional areas of the brain
what are the ways in which we can work out which regions control a particular function?
cytoarchitectural studies post-mortem studies intraoperative electrocortical stimulation medical imaging animal studies
what is Intraoperative electrocortical stimulation?
awake brain surgery, stimulate an area of the brain with electrodes and ask the patient the effect of this, this is also useful to ensure during brain surgery there is no damage to functional areas. Forms topographic maps.
what are the 2 arteries responsible for the blood supply to the brain?
internal carotid artery
vertebral arteries
describe the path of the internal carotid artery?
arteries originate at the bifurcation of the left and right common carotid arteries
They move superiorly within the carotid sheath, and enter the brain via the carotid canal of the temporal bone.
Once in the cranial cavity, the internal carotids pass anteriorly through the cavernous sinus.
The internal carotids then continue as the middle and anterior cerebral artery
describe the path of the vertebral arteries?
The right and left vertebral arteries arise from the subclavian arteries, medial to the anterior scalene muscle. They then ascend the posterior aspect of the neck, through foramen transversarium (holes in cervical vertebrae).
The vertebral arteries enter the cranial cavity via the foramen magnum.
The two vertebral arteries converge to form the basilar artery.
The basilar artery terminates by bifurcating into the posterior cerebral arteries.
what are the components of the circle of willis?
anterior cerebral arteries, internal carotid arteries, posterior cerebral arteries, anterior communicating artery and posterior communicating artery.
what is the anterior communicating artery?
the artery which connects the 2 anterior cerebral arteries
what is the posterior communicating artery?
the artery which connects the internal carotid artery to the posterior cerebral artery
what does the middle cerebral artery supply blood to?
portion of the frontal lobe and the lateral surface of the temporal and parietal lobes, including the primary motor and sensory areas of the face, throat, hand and arm, and in the dominant hemisphere, the areas for speech.
what does the anterior cerebral artery supply blood to?
most midline portions of the frontal lobes and superior medial parietal lobes.
what does the posterior cerebral artery supply blood to?
medial and lateral parts of the posterior cerebrum including the occipital lobe
describe the venous drainage system of the brain
dural venous sinuses drain the CNS, face and scalp. they ultimately drain into the internal jugular vein.
what gives rise to the anterior, superior and inferior cerebellar arteries?
the basilar artery
what is the pre-central gyrus?
what is its function?
primary motor cortex
for executing voluntary moveemnts
what is the post-central gyrus?
primary somatosensory cortex
what is the motor homunculus?
a topographic representation of the body parts and its correspondents along the precentral gyrus of the frontal lobe
what is the sensory homunculus?
a topographic representation of the body parts along the postcentral gyrus of the parietal lobe
why do we need a motor and sensory homunculus?
as some parts of the body you can feel but can’t move e.g. scalp
where is the supplementary motor cortex?
just anterior to the primary motor cortex (brodmanns region 6)
what is the function of the supplementary motor cortex?
contributes to the control of movement
what happens if we get a lesion of the primary motor cortex?
contralateral flaccid paralysis which partially recovers
what happens when we get a lesion of the supplementary motor cortex?
contralateral rigid paralysis and an increase in deep tendon reflexes
which Brodmann region is the frontal eye field?
8 in frontal cortex
what happens when you get a lesion in the frontal eye field?
difficulty moving eyes to opposite side
which brodmanns region is the primary motor cortex?
4
what brodmanns areas are the primary somatosensory cortex?
3,2 and 1
what does a lesion in the primary somatosensory cortex cause?
decrease in contralateral touch, pressure and proprioception
what is Brodmann’s area 40?
supramarginal gyrus
what happens if we get a lesion at the supramarginal gyrus?
tactile and proprioceptive agnosia, loss of left-right discrimination, contralateral hemineglect and contralateral apraxia
what is the function of Brodmann’s area 39?
language perception
what would a lesion at Brodmann’s area 39 cause?
Alexia, dyslexia or agraphia
what is hemispheric lateralisation?
the idea that the two halves of the brain are functionally different and that each hemisphere has functional specialisations
how are the 2 hemispheres of the brain connected?
nerve fibres called the corpus callosum
which is the dominant hemisphere?
the one in which language comprehension occurs (most often left)
what functions are the left and right hemispheres usually dominant for?
the left hemisphere is dominant in terms of speech and language. the right hemisphere is dominant in terms of visual-motor tasks.
what can lesions of the dominant hemisphere cause?
language dysfunction
what is aphasia?
an inability to comprehend or formulate language because of damage to specific brain regions
what is broca’s area?
a region in the frontal lobe of the dominant hemisphere, usually the left, of the brain with functions linked to speech production
what is Wernicke’s area?
the region of the brain that is important for language development. It is located in the temporal lobe on the left side (usually) of the brain and is responsible for the comprehension of speech
what would happen if you had a lesion in the Broca’s area?
you would know what to say but have difficulty expressing it, you would have slow laboured speech, you would delete prepositions, nouns and you would be non-fluent as the transitions would feel difficult.
what would happen if you had a lesion in Wernicke’s area?
you would hear but wouldn’t be able to understand, you would have fluent effortless speech with lots of un-known mistakes, you would not be able to understand your own words and you would produce new words.
how are Broca’s and wernickes areas connected?
a bundle of nerve fibers called the arcuate fasciculus.
what is the Sylvian fissure?
separates the frontal and parietal lobes superiorly from the temporal lobe inferiorly aka lateral sulcus
where would we find the arcuate fasciculus?
around the Sylvian fissure
what deficits would occur if we had a lesion in the middle cerebral artery?
contralateral upper limb weakness, partial blindness, global aphasia, contralateral hemineglect, decreased self awareness
what deficits would occur if we had a lesion in the anterior cerebral artery?
contralateral lower limb weakness, contralateral sensory loss, frontal lobe behavioural abnormalities, contralateral hemineglect
what deficits would occur if we had a lesion in the posterior cerebral artery?
contralateral partial blidness, contralateral hemisensory loss and hemiparesis (weakness on one side of the body)
what is the neocortex?
the centre for higher brain functions e,.g. perception, decision-making, language
what are the pre-frontal cortex’s functions?
abstract thinking, decision making, planning, prioritising, sequencing, adaptive and goal directed behaviour
what would lesions in the pre-frontal cortex cause?
disinhibition. subtle personality changes, decreased concentration/judgement/abstract thought/foresight/tact/problem solving/initiative
what is the Pareto-occipital sulcus?
it separates the parietal and occipital lobes
what is the function of the calcimine sulcus?
primary visual cortex
what is either side of the calcimine sulcus?
accessory visual cortexes
