pontocerebellum and damage Flashcards
Role of the pontocerebellum
governance of voluntary movement and motor learning
pontocerebellum does not receive what?
projections from peripheral receptors
Afferent projections to the pontocerebellum originate from where?
in the motor and association corticies of the cerebrum via cortico-pontocerebellar projections
Where do cortico-pontocerebellar projections descend from?
motor association cortex likely supplementary and premotor cortex
what do cortico-pontocerebellar projections descend through? end on?
internal capsule and medial third of cerebral peduncle to end on neurons of pontine nuclei
pontine nuclei axons decussate to enter the cerebellum through what structure?
contralateral middle cerebellar peduncle
pontine nuclei rise to the cortex as what type of fibers?
mossy fibers
where do mossy fibers end?
on granule cells of the lateral cerebellar cortex
where do mossy fiber collaterals end?
on neurons in the dentate nucleus
what type of information does cortico-pontocerebellar pathways carry?
information that the cerebellum uses for movement initiation and execution
lesions of the corticopontine pathway or pontine nuclei result in what deficits?
contralateral deficits in the arm and leg coordination
lesion of the cerebellar peduncle results in what deficits?
ipsilateral deficits in the arm and leg coordination
Where does pontocerebellum cortex project to first?
dentate nuclei
after the dentate nuclei, where do pontocerebellum cortex project? via what?
via the superior cerebellar peduncle to:
contralateral red nucleus
contralateral VL thalamus
Where do dentate projections to the red nucleus end?
on parvocellular neurons which project to the inferior olivary nucleus which then project back into the cerebellum providing regulatory feedback to the cerebellum
After dentate projections go to the contralateral VL thalamus, they then project to what? produces?
motor and premotor cortex which produces direct and indirect actions on UMN via corticospinal pathways and corticobulbar pathways
Function of the pontocerebellum is in what?
movement initiation
when the dentate nucleus was damaged, what functions were lost?
voluntary execution of movement was delayed
the known delay of execution of movement after damage to the dentate nucleus suggests what?
that these projections are essential for the initial activation of corticospinal neurons at the beginning of a movement
What does damage to the pontocerebellum produce?
a delay of excitatory output from the motor cortex resulting in a corresponding delay in muscle contraction
What is lost besides activation of both agonist and antagonist muscle with damage to pontocerebellum?
reciprocal pattern of activation in agonists and antagonists that accompanies many movements
What role does the pontocerebellum play in muscle activation?
timing
pontocerebellum also influences contraction how?
influences the duration of the muscle contraction
damage to the cerebellar cortex alone results in permanent motor damage, true or false?
false.
damage to the cortex rarely results in permanent damage
damage to the cortex of the cerebellum AND nuclei or to nuclei alone results in what?
a wide range of motor problems
unilateral lesions of the cerebellum result in _______ deficits.
ipsilateral
right dentate and interposed nuclei influence what?
the LEFT motor cortex and red nucleus
the left motor cortex and red nucleus project to what side of the spinal cord?
right (therefore lesions produce ipsilateral deficits)
What do lesions of the lateral cerebellum result in?
deterioration of coordinated movement referred to as movement decomposition or dyssynergia
the deficit of dyssynergia consists of what?
the breakdown of movement into its individual component parts
dyssynergia s/s?
hypotonia (decrease in muscle tone and in DTRs)
ataxia (uncoordinated limb movement)
ataxia with cerebellar damage includes specific symptoms of?
unsteady gait
tendency to lean or fall to the side of the lesion
dysarthria
ocular motor coordination defects
dysmetria- past pointing when pointing at stationary or moving objects
What type of tremor is associated with cerebellar damage?
intention tremor
what is an awkward performance of rapid alternating movements associated with cerebellar damage?
dysdiadochokinesia
also manifested by inability to perform repeated rhythmic movements
What is sensory cerebellar ataxia?
- disruption of proprioceptive afferents
- worsening coordination of movement when eyes are shut
- positive Romberg sign
- problems walking in the dark
What is motor cerebellar ataxia?
damage to the cerebellum itself
ataxia symptoms exist with or without vision
