Cerebellum Lecture Flashcards
Main function of the cerebellum
- Motor coordination and correction
- Maybe motor memory component
- able to test directly
Main function of the Basal Ganglia
- Initiation Selection of Motor Programs
- Cannot test directly
Corticospinal tracts
One long axon. Modulation is performed by spinal cord, thalamus (BG and cerebellum)
where does the cerebral cortex send info to
- the spinal cord
- the BG
- Cerebellum
what does the BG send info to
- thalamus
- brainstem
what does the cerebellum send info to
- thalamus
- brainstem
what does the spinal cord send info to
the cerebellum and the thalamus
what is the motor control of the cerebellum
1) maintenance of balance and posture: Vestibular information/ proprioception
2) Coordination of multiple motor groups/ movement. Skilled movement
3) proprioception input: muscle spindle feedback (muscle proprioception
4) Postural Adjustments: Unconscious GTO
5) sensory processing
6) adaptability
7) automaticity: especially in posture
8) motor commands are not initiated in cerebellum; it modifies motor activity accuracy
Motor Learning of the Cerebellum
The cerebellum plays a major role in adapting and fine-tuning motor programs to make accurate movements through a trial-and-error process
Cognitive Functions of the Cerebellum
Involved with cognitive functions such as language. Historically it is considered part of the motor system but cognitive functions are not fully understood yet.
the 4 inputs of the cerebellum
1) anticipates the output of the motor command (coordination of joints)
2) requires proprioception from the muscle spindles
3) requires vestibular information for control of balance and equilibrium
4) controls eye reflexes (fixation on a target and eye coordination
what is the forward model of the cerebellum
predicts the sensory outcome of our movement and actions
The accuracy in time sensorimotor coordination
- is like a copy machine: It creases a replica of our movement in time and produces a “likeness of the pattern”
- If the motor performace has error: the cerebellum corrects via error based learning
Essential aspects of sensorimotor coordination of the cerebellum
- timing
- onset and offset of muscle activation
- direction of movement
although the cerebellum accounts for (x%) of the brains volume, it contains over (y%) of the total number of neurons in the brain
x 10%
y 50%
what sensory input helps compensate for shifts in the body position of changes in load upon the muscles
input from the vestibular receptors and muscle proprioceptors (muscle spindle and GTO)
Lobes of the Cerebellum
medial to lateral
1) vermis
2) intermediate zone
3) lateral hemisphere
inferior
4) flocculonodular lobe
what does the flocculonodular lobe connect directly to
the vestibular system
function of the flocculonodular lobe
1) transport vestibular information
2) equilibrium balance
3) posture
Lateral hemisphere function and motor pathway
function: motor planning for extremities
Pathways: lateral corticopinal tracts
Intermediate hemispheres function and motor pathway
function: distal limb coordination
pathways: lateral corticospinal tract and rubrospinal tract
vermis function
proximal limb and trunk coordination
flocculonodular lobe funciton
balance and vestibuloocular reflexes
Purkinje Cells
output from the cerebellum
inhibitory
Climbing fibers
input to the cerebellum from olive
excitatory
Mossy fibers
input to the cerebellum
excitatory
Main cerebellar input pathways
1) vestibular input: balance and equilibrium
2) visual (corticopontine fibers)
3) proprioceptive and somatosensory (corticopontine fibers)
4) motor efference copy
Main cerebellar outputs
1) thalamus
2) hippocampus
3) superior colliculus
4) premotor areas
5) primary motor area
6) posterior parietal cortex
function of the superior colliculus
learning memory and connections
direct vestibular cerebellar connections
From vestibular receptors in the semicircular ducts - Vestibular ganglion - into rostral medulla - vestibular complex - follocculonodular
inputs tracts to the cerebellum
1) ventral spinocerebellar
2) Dorsal spinocerebellar
3) cuneo spinocerebellar
4) rostral spinocerebellar
Ventral Spinocerebellar Tract
- from LE
- leg interneuron
- coordinates movement and posture
- unconscious perception
- crosses twice
Dorsal Spinocerebellar Tract
- from LE
- leg proprioceptors
- Carry MS and GTO info (1a and 1b)
- carry proprioception, touch, and pressure sensation
- stays unilateral
Rostral Spinocerebellar Tract
- from UE
- information for coordinated movement
- Arm interneurons
- unilateral tract
Cuneo Spinocerebellar Tract
- From UE
- arm proprioceptors
- 1a MS proproceptive, touch and pressure sensation
- unilateral tract
Cerebellum outputs
- no direct connection from the motor system
1) red nucleus to spinal cord
2) ventrolateral nucleus (VLN) of thalamus to cortex
what areas of the cortex does the ventrolateral nucleus of the thalamus connect too
- premotor cortex
- supplementary cortex
- prefrontal association area
Function: to in in postural control, smooth movements, feedback for error
lesions of the cerebellum will present problems on what side
the unilateral side
Deficits in cerebellar function
- uncoordination and problems maintaining balance and posture
- decomposition of movement
-Intention tremor
decomposition of movement definition
- unable to produce coordinated and smooth movements.
- Loss of feedforward mechanism , does not allow or temoral timing of the activated muscles, force or awareness in space
- Ataxia
Intention tremor
when making a movement toward a target the pt might produce an involuntary movement tremor that increases as they approach closer to the target
Types of Cerebellar Testing
- Finger to nose
- Heel to shin
- Dysdiadochominesia (RAM)
- Romberg
- Rapid finger tapping movements
What do look for in cerebellar exams
- speed, coordination, timing (heel to shin) and (finger to nose)
Dysrhythmia
abnormal timing
Dysmetria
overshoot or past pointing
Dysdiadochokinesia
RAM (supination and pronation)
Overshooting
holding a testing position and suddenly letting go
Truncal ataxia
ataxia in gait
postural dysfunction in cerebellar disorders
- high fall risk
- loss of automatic movements
- loss of ankle, hip strategies (due to lack of muscular timing)
- static and dynamic posture
- may have increased tone or reflexes
Hypotonia
low tone from loss of MS and GTO input
slow generation of force
unable to produce timely force generation (5/5 strength throughout but mild slowly)
loss of RAM
inability to produce RAM
Deficits in motor learning
loss of the ability to anticipate (feedforward) or correct (feedback) because of loss of proprioceptive, sensory and muscle force
how does the cerebellum predict sensory and motor outcomes of a task
sensory via: MS and GTO
Motor: input from vision: task is an error
