Lecture 6.1 Flashcards
somatotopic organization
where the third order neuron in the thalamus projects to in the somatosensory cortex depends on where the corresponding sensory neuron in the body originated
what is the amount of cortex representing each body part proportional to
the amount of sensory neurons providing input
what does damage to the cerebellum lead to
impairments in motor control and posture on the ipsilateral side of the body
- balance disorders; subjects develop postural strategies such as a wide-based stance to compensate for
cerebellum general function
monitor ongoing movement and modify motor signals of the descending pathways to adapt movements and make them more accurate
does the cerebellum initiate motor commands?
no
what types of muscle coordination does the cerebellum monitor and modify
- maintenance of balance and posture
- correction of voluntary movements
- motor learning
how does the cerebellum modulate commands to motor neurons?
through input from vestibular receptors and proprioceptors
why does the cerebellum modulate commands to motor neurons
to compensate for shifts in body position or changes in load upon muscles
how does the cerebellum correct voluntary movements
- coordinates timing and force of different muscle groups to produce fluid limb or body movements
- compares intended and actual movements, adjusts for errors, and corrects ongoing movements
how does the cerebellum function in motor learning
- adapting and fine-tunes motor programs through trial-and-error
what kind of shift does motor learning require
conscious —> unconscious
folia
finely spaced parallel grooves which form a continuous thin layer of tissue tightly folded like an accordion
what does the telencephalon become in adult brain structures
cerebrum: cerebral hemispheres (cortex, white matter, basal nuclei)
what does the diencephalon become in adult brain structures
diencephalon (thalamus, hypothalamus, epithalamus), retina
what does the mesencephalon become in the adult brain
brain stem: midbrain
what does the metencephalon become in adult brain
brainstem: pons
what does the cerebellum develop from
the rhombic lips (the edges of the 4th ventricle); as the tissue thickens with growth it folds over creating the 4th ventricle space
what does the myelencephalon develop into in the adult brain
brain stem: medulla oblongata
what is the roof of the 4th ventricle formed by
cerebellum
what is the floor of the 4th ventricle formed by
brainstem (pons and medulla)
what are the walls of the 4th ventricle formed by
cerebellar peduncles
what is the first step of cerebellum development
5th week: rhombic lips expand significantly and project caudally over the roof plate of the 4th ventricle
second step of cerebellum development
rhombic lips fuse with each other in the midline to form the cerebellar plate
third step of cerebellum development
12th week: cerebellar plate has formed the small midline vermis and two lateral hemispheres can be seen
where does the gray matter lie in the cerebellum
externally in the cortex
where is the white matter in the cerebellum
internal, called the medulla
deep nuclei
centrally located nuclei within the deep white matter/medulla
what does the cerebellar cortex consist of
gray matter
what does cerebellum medulla consist of
incoming and outgoing myelinated axon fibers projecting to and from the cerebellar cortex
three cerebellar cortex layers
- granule cell layer
- Purkinje neuron layer
- molecular layer
what cells are found in the granule layer
tightly packed granule neurons
what cells are found in the Purkinje neuron layer
Purkinje neurons; only one cell thick
what cells is the molecular layer composed of
axons of granule neurons and the dendrites of Purkinje neurons as well as dendrites from a few other neuronal types (no somas)
main characteristic of Purkinje cells
one of the largest neurons in the human brain w/ an elaborate branching dendrites that are only found in cerebellum
arbor vitae
sensory and motor white matter tracts within cerebellum
three cerebellar peduncles
- superior peduncle: connects to midbrain
three cerebellar peduncles
- superior peduncle: connects to midbrain
- middle peduncle: connects to pons
- inferior peduncle: connects to medulla (technically at the ponto-medullary junction)
superior cerebellar peduncle (SCP)
- connects cerebellum to midbrain/mesencephalon
- carries efferent tracts leaving the cerebellum (does receive some ascending tracts)
middle cerebellar peduncle (MCP)
- connects pons to the contralateral hemisphere of the cerebellum via corticopontine tract through transverse pontine fibers
- contains largest number of nerve fibers; largest peduncle
inferior cerebellar peduncle (ICP)
- connects cerebellum to medulla
- carries afferent tracts entering cerebellum from spinal cord and brainstem
- carries efferent tracts leaving cerebellum to vestibular nuclei and inferior olives in brainstem
how does posterior spinocerebellar tract enter the cerebellum
inferior cerebellar peduncles (medulla)
how does cuneocerebellar tract enter cerebellum
inferior cerebellar peduncles (medulla)
how does anterior spinocerebellar tract enter cerebellum
superior cerebellar peduncles
three lobes of cerebellum
anterior lobe, posterior lobe, flocculonodular lobe
what fissure separates anterior and posterior lobes
primary fissure
what fissure separates the flocculonodular and posterior lobes
posterolateral fissure
vermis
unpaired, medial portion of the cerebellum that connects the two hemispheres
how many vermis lobules
nine
how many horizontal lobulea
nine
which lobules does the flocculonodular lobe contain
X and HX
what is lobule HVII (the largest lobule) separated into
HVIIb, Crus-I, and Crus-II
what 3 regions can the cerebellum be subdivided into based on function
- vestibulocerebellar
- spinocerebellar
- cerebrocerebellar
vestibulocerebellum anatomical parts
flocculonodular lobe, some posterior lobe, and adjacent vermis
vestibulocerebellum function
regulates balance and eye movements
spinocerebellum anatomical parts
vermis and intermediate/midline parts of the hemispheres
spinocerebellum function
regulation of muscle tone & coordination of skilled voluntary movement (matching of intended movement with proprioceptive input of actual body position)
cerebrocerebellum anatomical parts
lateral parts of the hemisphers
cerebrocerebellum function
planning of movement; has non-motor cognitive functions as well
where does vermis mainly receive input from
spinocerebellar tracts in the trunk of the body
what info does the vermis receive from the spinocerebellar tracti
info on the position & balance of torso
where does vermis project to
fastigial deep nuclei of the cerebellum
where does the fastigial deep nuclei of the cerebellum send output to
vestibular nuclei in the brainstem for maintenance of balance
is cerebellum mainly ipsilateral or contralateral
ipsilateral
four major deep nuclei within cerebellar medulla
- dentate nucleus
- 2 interposed nuclei
- fastigial nucleus
main function of neurons in the deep nuclei
prime output from cerebellum
where do the fibers of the flocculonodular lobe send output to
directly synapse onto vestibular nuclei
mnemonic to remember names and positions of deep cerebellar nuclei relative to their position from the midline
Don’t eat greasy food: dentate —> emboliform —> globose —> fastigial
interposed nucleus
emboliform + globose; some animals don’t have distinct emboliform and globose nuclei and instead have a single fused one
what info do dentate nuclei receive
info related to tasks requiring fine dexterity from the cerebral cortex and is important for the regulation of voluntary motor activity: timing, planning, and inception
where does dentate nuclei project to
red nucleus and ventrolateral thalamic nucleus
what sensory input do interposed nuclei receive
spinal, somatosensory, auditory, and visual info input
where do interposed nuclei neurons project
red nucleus in brainstem
what are fastigial nuclei associated with
vermis
where are fastigial nuclei found
along midline of cerebellum
what input do fastigial nuclei receive
spinocerebellar afferent input
where do vestibular nuclei neurons project to
vestibular nuclei in brainstem and sends efferent fibers to proximal and trunk muscles for maintenance of balance
primary inputs to cerebellum
cerebral cortex —> pons —> cerebellum
vestibular inputs —> cerebellum
inferior olive —> cerebellum
spinal cord —> cerebellum
what kind of info do vestibular inputs, inferior olive, and spinal cord send to cerebellum
sensory, proprioceptive, and vestibular ipsilateral info
what kind of info does cerebral cortex send to cerebellum
motor cortex, association frontal cortex, sensory cortex
primary output path of cerebellum
cerebellar cortex (Purkinje neurons) —> deep nuclei (main output) —> thalamus (—> cerebral cortex), vestibular nuclei, inferior olive, red nucleus
first step of descending motor tract coordination and correction by the cerebellum
motor cortex sends action potentials to lower motor neurons in the spinal cord
second step of descending motor tract coordination and correction by the cerebellum
action potentials from the motor cortex inform the cerebellum of the intended movement
third step of descending motor tract coordination and correction by the cerebellum
lower motor neurons in the spinal cord send action potentials to skeletal muscles, causing them to contract
fourth step of descending motor tract coordination and correction by the cerebellum
proprioceptive signals from the skeletal muscles and joints to the cerebellum convey info concerning the status of the muscles and the structure being moved during contraction
fifth step of descending motor tract coordination and correction by the cerebellum
cerebellum compares info from motor cortex w/ proprioceptive info from skeletal muscle joints
sixth step of descending motor tract coordination and correction by the cerebellum
action potentials from the cerebellum to the spinal cord modify the stimulation from the motor cortex to the lower motor neurons
seventh step of descending motor tract coordination and correction by the cerebellum
action potentials from cerebellum are sent to motor cortex to modify motor activity
what do steps 1 and 3 of descending motor tract coordination and correction by cerebellum involve
descending tracts
what do steps 2 and 4-7 of the descending motor tract coordination and correction by cerebellum involve
cerebellum monitoring, comparing, and correcting intended vs actual movement
cerebellum motor function
predicting motor commands and outcomes (movements) and using sensory data about body position for future error correction/predictions
cerebellar non-motor function
calculating and monitoring predicted sensory/social/language/threat outcomes with actual sensory data and updating predictions based on this (non-motor error correction)
why is prediction the most important functions of the brain
- optimizes neurocognitive resources
- adapts to surrounding environment and ensure survival
- goes beyond motor adaptability to everything from language usage to adaptive social behaviors to appropriate response to threat
example of proposed model for cortical-cerebellar and cerebellar-cortical interactions
cerebellum estimates sensory state of the body by anticipating the consequences of a motor command as a means to compensate for the slower time-scale in which sensory feedback signals are processed in cerebral cortex
example of proposed model for cortical-cerebellar and cerebellar-cortical interactions
cerebellum estimates sensory state of the body by anticipating the consequences of a motor command as a means to compensate for the slower time-scale in which sensory feedback signals are processed in cerebral cortex
