Cerebrum Flashcards
In which layer of the cerebrum are cell bodies found?
layer IV
example of what short association fibers connect
premotor cortex to primary motor cortex
what do long association fibers connect?
limbic lobe to frontal lobe
what do commissural fibers connect? Where are these fibers found?
- connect right and left hemisphere
- found in corpus callosum
what structure do the axons of projection fibers pass through?
coronal radiata
From the anterior limb of the internal capsule to the posterior limb, what is the order of innervation? Which parts are innervated by the corticospinal tract? corticobulbar tract?
- ant to post: Face (+ head) > Arm > Thorax > Abdomen > Lower limb [hint: FATAL]
- corticobulbar: face (anterior limb)
- corticospinal: arm, thorax, abdomen, lower limb (posterior limb)
Which layer of the cerebrum is the origin of projection fibres to extracortical targets, such as BG, thalamus, brainstem, spinal cord?
layer V
In the primary motor cortex of the frontal lobe, layer V of the cerebrum contains ________ cell bodies?
Corticospinal tract (UMN)
function of frontal lobe
- higher cognitive function
- motor planning/executive
- language
function of limbic system
emotional, social, sexual behaviour
function of parietal lobe
- somatic sense of body image
- 3D localization of self and targets in space
- language
function of the occipital lobe
vision
function of temporal lobe
- short-term memory
- learning
- auditory
Which lobe is affected in body dysmorphia
parietal lobe
Pierre Broca’s contributions
- language in left hemisphere
- lesion causes nonsensical speech
- Broca’s area = speech production
Karl Wernicke’s contributions
- understanding language in the posterior portion of the left temporal lobe
- lesion allows fluent speech but speech was incoherent/made no sense (i.e. patient cannot understand question)
- Wernicke’s area = language comprehension
Which speech area is affected in receptive aphasia? expressive aphasia?
receptive = wernicke’s
expressive = broca’s
Which white matter tract connects wernicke’s to broca’s? What kind of aphasia results from a lesion here?
- arcuate fasciculus
- conduction aphasia (impairment of speech repetition after hearing it, but good spontaneous speech)
What are the steps to vocally respond to a verbal question? Which parts of the brain are involved in each step?
- Listen (primary auditory cortex)
- Comprehend (Wernicke’s)
- send association fibers through Arcuate fasciculus to…
- Formulate speech (Broca’s)
- Activate UMN for speech muscles (primary motor cortex)
Lesions to association cortex lead to?
agnosias, aphasias, apraxias
agnosias
inability to recognize common objects
aphasias
inability to understand speech
apraxias
inability to execute purposeful movements (motor planning disorder)
what results from parietal association cortex lesion? provide an example
- tactile agnosia - defect in ability to interpret tactile sensation (but may still feel an object)
- e.g. shut eyes and hold object = cannot identify it
astereognosia? which association cortex is lesioned?
- “tactile amnesia” - loss of awareness of the spatial relations of parts of the contralateral side of the body
- posterior parietal cortex
cortical neglect? Which association cortex is lesioned?
- extreme form of astereognosia; patient denies one side of the body and the corresponding visual field
- posterior parietal cortex
What does damage to the ventral stream visual association fibers cause?
impairment of identifying:
- colour
- letters
- faces
- visual memories
What does damage to the dorsal stream visual association fibers cause?
impairment of:
- 3D visual understanding of object
- understanding motion of object
What happens when there is bilateral destruction of the auditory association cortex?
fail to identify and respond to sounds, but can still hear
amusia
right-side lesion to the auditory association cortex –> inability to recognize previously familiar voices and music
What structures does the primary olfactory area include?
- uncus
- parts of insula
- frontal gyri
anosmia
loss of smell
why does anosmia lead to lack of taste sensation?
olfactory and gustatory association cortices intermix
(hint: anosmia = loss of smell)
What does lesion to the limbic association cortex lead to?
- schizophrenia
- depressive illness
lesions to which hemisphere lead to aphasias? agnosias?
left lesion = aphasia
right lesion = agnosia
lesions to which hemisphere are more detrimental?
left lesion = more detrimental
How is neural information converted to physical energy in motor systems? Which parts of the brain are involved?
- IDENTIFICATION and LOCALIZATION of targets in space –> post parietal cortex
- formulation of PLAN of action –> premotor cortex and supplementary motor cortex (SMA)
- EXECUTION of movement –> primary motor cortex
What does an upper motor neuron lesion lead to?
disinhibition of the LMN (cannot activate or inhibit it) –> SPASTIC PARALYSIS (rigidity/contraction of all LMN muscles)
what does a lower motor neuron lesion lead to?
no electrical input to muscles –> FLACCID PARALYSIS (relaxation of all muscles)
Is conscious motor organized in a hierarchical or parallel fashion? Which tracts are involved? Are these tracts pyramidal or extrapyramidal?
- hierarchical
- tracts: corticospinal, corticobulbar
- pyramidal tracts
Is unconscious motor organized in a hierarchical or parallel fashion? Which tracts are involved? Are these tracts pyramidal or extrapyramidal?
- parallel
- tracts: corticoreticular, reticulospinal, vestibulospinal, rubrospinal
- extrapyramidal tracts
what are the extrapyramidal tracts?
- corticoreticulospinal
- vestibulospinal
- rubrospinal
- tectospinal
what is the corticoreticulospinal tract responsible for?
(+) to leg extensors and arm flexors
what is the vestibulospinal tract responsible for?
(+) to arm/leg extensors
(-) to arm/leg flexors
what is the rubrospinal tract responsible for?
- (-) to arm extensors
- (+) to arm flexors
- no effect on leg muscles
what is the tectospinal tract responsible for?
neck muscles
What is lesioned in decorticate posturing? which tracts are active? Which tracts are inactive? Describe overall posture.
- CST lesion (at top of brainstem)
- extrapyramidal tracts are all functional
- rubrospinal tract = flex upper body
- corticoreticulospinal tract = flex upper body, extend lower body
- vestibulospinal tract = (+) limb extensors (arm extensors overruled by reticulospinal and rubrospinal tracts), (-) limb flexors (i.e. arms and legs extended)
- posture: arms flexed with flexed fingers and wrists on chest, legs stiffly extended and internally rotated, plantar flexion of feet
What is lesioned in decerebrate posturing? which tracts are active? Which tracts are inactive? Describe overall posture.
- brainstem lesion
- CST and rubrospinal are NOT active
- corticoreticulospinal tract = flex upper body (overruled by VST) , extend lower body
- vestibulospinal tract = (+) limb extensors, (-) limb flexors (i.e. arms and legs extended)
- posture: arms extended with wrists and fingers flexed, legs stiffly extended, plantar flexion of feet
What kind of lesion can cause decorticate posturing? decerebrate posturing?
- decorticate: uncal/temporal herniation ABOVE tentorium cerebelli
- decerebrate: uncal/temporal herniation BELOW tentorium cerebelli
