The Cerebrum Flashcards
lateral sulcus
aka Sylvian fissure; separates frontal and parietal lobe from temporal lobe below
central sulcus of Rolando
separates frontal and parietal lobes, bordered by precentral gyrus (motor) and postcentral gyrus (sensory)
function of precentral vs postcentral gyrus
precentral gyrus = motor
postcentral gyrus = sensory
the primary visual cortex is subdivided by the horizontally oriented ____ sulcus
calcarine sulcus
parts of which lobes make up the limbic lobe
frontal, parietal, temporal
the limbic lobe makes a rim around the…
diencephalon (lying in lateral wall of third ventricle)
the anterior end of each temporal lobe is formed by a rounded projection called the ___, lies above the almond shaped ____
uncus lies above amygdala
the cortex that sweeps over top of the limbic lobe is the
cingulate gyrus, aka limbic system cortex
what are the parts of the corpus collosum
rostrum (most inferior)
genu (most anterior)
body
splenium (most posterior)
the large area in front of the primary motor cortex is the
pre-motor or supplemental motor cortex
how does histological structure of association cortex differ from the restricted areas of the cerebrum?
association cortexes are homotypical- all 6 layers of neuronal structure are similar in thickness
restricted areas have varying thicknesses (heterotypical)- primary sensory cortex is “granular” cortex, motor cortex is “pyramidal” cortex
what layer is thickest in the primary sensory cortex
granular cells (layers 2 and 4)
what layer is thickest in primary motor cortex
pyramidal cells (layers 3 and 5)- give rise to axons of corticospinal and corticobulbar tracts
Brodmann areas 3, 1, 2
three regions of primary somatosensory cortex (in order 3, 1, 2 from anterior to posterior)
Brodmann area 4
primary motor cortex
Brodmann area 17
primary visual cortex
Brodmann areas 41 and 42
primary auditory cortex
Brodmann areas 44 and 45
Broca’s area
Brodmann area 22
Wernicke’s area
Brodmann area 6
premotor cortex
on the medial extension of both the primary somatosensory and motor cortexes is control for what body area?
lower limb (contralateral)
the most inferior portion of the homunculus for both the primary somatosensory and motor cortexes is for what body area
face
virtually all of the lateral aspect of each brain hemisphere is in the vascular territory of branches of the…
middle cerebral artery
supplying blood to the upper half of both the motor and somatosensory homunculus (primary cortexes) is that
middle cerebral artery branches
the medial aspect of the primary motor and somatosensory cortexes (where lower limb is controlled) is supplied with blood via the…
anterior cerebral artery
the motor and somatosensory homunculus have a dual arterial blood supply… describe
most of vascular supply is middle cerebral artery, except for medial aspect which is supplied by anterior cerebral artery
effect of vascular injury or blockage of middle cerebral artery on the motor and somatosensory homunculus’?
motor- contralateral upper body, upper limb, and lower face (not upper face because of bilateral motor innervation via cranial nerves) spastic weakness
sensory- contralateral face and upper body loss of sensation
effect of vascular injury or blockage of anterior cerebral artery on motor and somatosensory homunculus’?
anterior cerebral artery only supplies medial portion- some trunk and lower limb
motor-contralateral lower limb spastic weakness (hyperactive muscle stretch reflex, upgoing toes- lost inhibition)
sensory- contralateral lower trunk/ limb loss of sensation
the distal ends of the middle cerebral artery and the anterior cerebral artery come together in a…
watershed zone- found at distal ends of 2 circulations
watershed zone
found at distal ends of 2 circulations
what part of the motor and somatosensory homunculus are in the watershed zone (of middle cerebral and anterior cerebral arteries)?
trunk portion
watershed infarct
sudden drop in overall arterial blood pressure
effect of watershed infarct on the motor and somatosensory primary cortexes?
watershed zone at distal ends of middle cerebral and anterior cerebral arteries, trunk area of both homunculus is in the watershed zone
infarct results in person in a barrel syndrome- bilateral trunk weakness and bilateral trunk sensory loss
person in a barrel syndrome
bilateral trunk weakness and bilateral trunk sensory loss due to watershed infarct affecting trunk area of both motor and somatosensory homunculus
how are the large purkinje cells of the cerebellum affected by global ischemia, resulting from sudden drop in arterial pressure (such as watershed infarct)?
purkinje cells of cerebellum are very sensitive to disruption in blood supply (consume large amounts of oxygen). these are involved in memory processing with hippocampus, so patients with temporal lobe watershed infarct have negative effect on memory processing
Brodmann area 8 is associated with generating
horizontal gaze (contralateral saccadic rapid eye movement) via activation of CN III (oculomotor) and VI (abducens)
(this is the frontal eye field, at the middle frontal gyrus)
what are the respective roles of the premotor neurons and the supplementary neurons found in the premotor cortex at Brodmann area 6?
premotor neurons- motor planning
supplementary neurons- mental rehearsal of movements
damage in these results in apraxia
apraxia
higher order motor deficit, disruption of learned movement execution despite intact motor function
(due to damage of premotor cortex)
frontal lobe syndrome
due to damage of prefrontal cortex (everything anterior to Brodmann area 6, where premotor cortex is)
changes in behavior, intelligence, cognition, or memory
where is the superior parietal lobule?
adjacent to primary somatosensory cortex (Brodmann area 1) in areas 5 and 7
processes high-order somatosensory information
(area 7 integrates sensory modalities for motor activities requiring hand-eye coordination. area 5 receives info from joins and muscles acting on those joints)
where is the angular gyrus
inferior part of parietal lobe, statistically more common in left parietal lobe
reading/simple math comprehension center
what do areas 5 and 7 of the superior parietal lobule do, respectively?
superior parietal lobe is adjacent to primary somatosensory cortex
area 5- receives info from joints and muscles acting on those joints to provide spatial information
area 7- integrates sensory info for motor activities requiring hand-eye coordination
lesions of superior parietal lobe (areas 5 and 7) cause forms of…
apraxia or astereognosis, such as:
ideational apraxia- loss of ability to organize the sequence of a pattern of movements
astereognosis- inability to identify object by just tactile modalities (feeling it in your hand)
buried in the lateral fissure (temporal lobe), in Brodmann areas 41 and 42, is…
primary auditory cortex
the primary visual cortexes are on the (lateral/medial) aspect of the occipital lobes
medial
the calcarine sulcus subdivides the primary visual cortex into…
cuneus gyrus (superior) and lingual gyrus (inferior)
the striate or primary visual cortex corresponds to what three Brodmann areas?
17- major (primary) visual cortex
18 and 19- adjacent extra striate cortical areas (going to parietal and temporal lobes)
a vascular insult or blockage or stroke involving what artery would affect primary visual cortex
posterior cerebral artery
causing contralateral homonymous hemianopsias with macular sparing (because of duel macular blood supply- posterior and middle cerebral arteries)
contralateral homonymous hemianopsia is caused by what and manifests as what?
blockage/injury to posterior cerebral artery supplying primary visual cortex in occipital lobe
presents with loss of visual field on one side of both eyes, but with macular sparing (bc of duel blood supply with middle cerebral artery)
where do the “what” and “where” visual pathways of the primary visual cortex project to, respectively?
“what” pathway (processing form and color)- temporal lobes (including fusiform gyrus between occipital and parietal lobes)
“where” pathway (processing movement and location)- parietal lobe
Balint’s syndrome
parietal lesion causing:
visual disorientation- inability to comprehend more than one aspect of a visual scene at a time
ocular apraxia- inability to focus on object of interest, difficulty initiation saccades and horizontal quick eye movements, tendency to over/undershoot visual targets
optic ataxia- difficulty reaching for an object under visual control, but can easily touch their own nose (so cerebellar function is intact)
patient presents with visual disorientation, optic ataxia, and ocular apraxia. where is the lesion likely to be located, and what is this called?
Balint’s syndrome- parietal lesion
visual disorientation- inability to comprehend more than one aspect of a visual scene at a time
ocular apraxia- inability to focus on object of interest, difficulty initiation saccades and horizontal quick eye movements, tendency to over/undershoot visual targets
optic ataxia- difficulty reaching for an object under visual control, but can easily touch their own nose (so cerebellar function is intact)
visual disorientation
inability to comprehend more than one aspect of a visual scene at a time
ocular apraxia
inability to focus on object of interest, difficulty initiation saccades and horizontal quick eye movements, tendency to over/undershoot visual targets
optic ataxia
difficulty reaching for an object under visual control, but can easily touch their own nose (so cerebellar function is intact)
lesions in temporal association cortex in the fusiform gyrus (between occipital and parietal lobes) results in inability to identify an object using just visual input, which is called ____, or inability to recognize familiar people by sight, which is called ___
visual agnosia- inability to identify an object using just visual input
prosopagnosia- inability to recognize familiar people by sight (specific form of visual agnosia)
Broca’s area is on the most inferior part of the left ____ lobe, and Wernicke’s area is on the posterior part of the left ___
Broca’s- frontal lobe (Brodmann area 44, 45)
Wernicke’s- temporal lobe (area 22)
the written comprehension center, found at Brodmann area 39, is…
angular gyrus
Broca’s area, Wernicke’s area, and angular gyrus are in the vascular territory of
left middle cerebral artery
aphasias may be caused by a stroke involving the superficial branches of the left…
middle cerebral artery
agraphia and dysgraphia
inability or difficulty (respectively) writing
common with patients with aphasia from left middle cerebral artery stroke
Broca’s area is adjacent to the UMN in the inferior part of the primary motor cortex, which bilaterally control the LMN in CN…
cranial nerves- vagus (X, palate, pharynx, larynx) and hypoglossal (XII, tongue)
patients with non-fluent or expressive aphasia have damage to what brain region
Broca’s area
difficulty putting together words to produce expressive speech in complete sentences
a patient presents with dysgraphia, though they can use their hand normally in other tasks. They appear to understand your request to repeat common phrases, but they cannot repeat the phrase and appear very frustrated. what does this patient likely have and where is the damage?
nonfluent/expressive aphasia- damage to Broca’s area
are aware of their aphasia
(dysgraphia- difficulty writing)
based on where Broca’s area is, a lesion here might also include adjacent primary motor cortex, resulting in a lesion in the ____ neurons, which generally only results in ____
may cause lesion in corticobulbar neurons
generally will only cause weakness of muscles in lower face due to bilateral innervation everywhere else
patient presents with fluent/receptive/sensory aphasia, though they do not seem frustrated by their condition. where is the damage?
Wernicke’s area. can still speak relatively fluently because Broca’s area is intact. however, may misuse words
T/F: patients with Wernicke’s area do not have trouble repeating phrases
FALSE: Broca’s area is intact, but they don’t understand you, so they don’t understand the directions to repeat
a patient comes in saying they think they need a hearing aid. you must repeat what you say to them frequently because they don’t seem to comprehend. They don’t seem frustrated about this other than saying they can’t hear you. where might the damage be?
Wernicke’s area (fluent aphasia)
probably also do have sensorineural hearing loss because Wernicke’s area is adjacent to primary auditory cortex, so they might have slight bilateral sensorineural hearing loss and difficulty localizing sound
but this is not the only issue
can patients who communicate via sign language present with apahsia?
yes. lesion to Broca’s area- motor sign aphasia, lesion to Wernicke’s- sensory sign aphasia
difficultly making signs or understanding someone else’s signs
consequence of stroke of left middle cerebral artery including only angular gyrus in left inferior parietal cortex?
this is area 39. results in Gerstmann’s syndrome.
inability to comprehend written language, and form of a/dysgraphia- difficulty expressing themselves in writing
alexia/dyslexia- difficulty reading
may also present with a/dyscalculia- difficulty with simple math problems
patient presents with alexia, dyscalculia, left-right disorientation, and finger agnosia. imaging shows an infarction of the left middle cerebral artery. where is the damage?
Gerstmann’s syndrome- damage to angular gyrus
(alexia- reading, dysgraphia- inability to express through writing)
(dyscalculia- difficulty with simple math)
(finger agnosia- can feel fingers but don’t recognize them as their own- higher order somatosensory deficit)
Gerstmann’s syndrome
damage to angular gyrus
present with alexia, agraphia, dyscalculia, left-right disorientation, and finger agnosia
may be due to stroke of left middle cerebral artery
a lesion or injury to the arcuate fasciculus, such as a stroke to the smaller branches of the left middle cerebral artery, would result in what type of apahsia?
conduction aphasia, or repetitive aphasia. Broca and Wernicke areas okay but not connected, so there is relatively fluent verbal output but patient misuses words, and patient cannot repeat words or execute verbal commands when asked to do so
You meet a patient who seems to misuse many words in their speech. You ask them to repeat the phrase “no ifs, ands, or buts”, but they cannot. You ask them to stand up, but they don’t seem to follow. You ask them to identify a pen, but they are not able to properly name the object. They don’t seem confused by what you are saying to them, but they are visibly frustrated. What might it be?
conduction (repetitive) aphasia due to damage of arcuate fasciculus
what do the areas of the right hemisphere that are located in the same relative locations as Broca’s and Wernicke’s area on the left do?
emotional content centers- adding emotion to speech (in area corresponding to Broca’s on left) and interpreting emotion in others’ speech (in area corresponding to Wernicke’s on left)
supplied by right middle cerebral artery
what might occur from a vascular insult of the branches of the right middle cerebral artery that supply the inferior portion of the frontal lobe and posterior portion of temporal lobe?
these areas correspond to areas of Broca’s and Wernicke’s on left, but on the right they are emotional content centers
lesion –> dysprosody (emotional expression/ interpretation deficits)
dysprosody
inability to express or identify affect/ attitude cues in speech
while on the left, lesion of the branches of the left middle cerebral artery affecting the angular gyrus results in Gerstmann syndrome, lesion of the right middle cerebral artery affecting the same respective area in the inferior right parietal lobe results in…
contralateral neglect- entirely lack awareness of the left side of the body (asomatognosia)
a women comes into clinic with makeup on just half of her face, though she doesn’t seem to notice. you ask her to draw a clock, and she crams all of the numbers on what side. what condition is this, and where might the damage be?
contralateral neglect, due to asomatognosia (lack of awareness of entire side of body)
damage is probably in the inferior right parietal lobe (corresponding location to angular gyrus on left side), and may be caused by stroke to right middle cerebral artery
the anterior and posterior limbs of the internal capsule come together at the ___
genu (bend, middle of the X)
medial to the posterior limb of the internal capsule is the egg-shaped ___, containing virtually all nuclei filtering subcortical information and heading out to sensory cortical areas
thalamus
which area of the internal capsule contains the diffuse axons that exit down from the prefrontal cortex, as well as the thalamocortical axons from the limbic thalamic nuclei going up to the prefrontal cortex?
anterior limb of internal capsule. difficult to localize a lesion to the anterior limb because of the diffuse nature of the axons going up/down through it
what kinds of axons run through the genu of the internal capsule?
exclusive location of all corticobulbar axons (for bilateral UMN innervation to LMN in cranial nerves)
what axons run through the posterior limb of the internal capsule? (4)
- corticospinal axons (topographically arranged, with arm fibers closer to genu than leg fibers)
- thalamocortical somatosensory axons coming from ventrobasal complex of thalamic nuclei (body wall somatic sensations) going to somatosensory cortex
- axons from medial geniculate body going to primary auditory cortex
- axons from lateral geniculate body going to primary visual cortex (most posterior)
all parts of the internal capsule (as well as thalamus and basal ganglia) are provided with blood by the small ____ branches arising from the proximal part of the ____
provided by small striate branches of the proximal part of the anterior cerebral, middle cerebral, and a bit of posterior cerebral arteries
major blood supply is lenticulostriate branches
major blood supply of internal capsule
lenticulostriate branches of anterior, middle, and posterior cerebral arteries
anterior choroidal artery branches also supply some blood
striate branches of the cerebral arteries (supplying the internal capsule) are particularly susceptible in HTN patients to what kind of stroke?
lacunar stroke (blockage of one of the small deep brain artery branches)
a lacunar stroke involving the posterior limb of the internal capsule would be particularly devastating why?
could result in:
- complete contralateral homonymous hemianopsia (visual radiations running through here)
- complete contralateral limb trunk hemiplegia (paralysis) (corticospinal fibers)
- slight bilateral sensorineural hearing loss (medial geniculate body)
a lacunar stroke to just the genu of the internal capsule would result in
contralateral lower face weakness (corticobulbar tract, but most provide bilateral innervation)
