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Functional Neuroanatomy > Task 3 - Cerebellum > Flashcards

Task 3 - Cerebellum Flashcards

1
Q

Cerebellum Purpose

A

Balance, smooth movements, timing of movements; corrects:

  1. gets info via afferent nerves from cortical areas
  2. gets spatial information from muscle spindles and other receptors (state estimation)
  3. sends feedback to motor areas
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2
Q

Cerebellar cortex

A

Cerebrocerebellum
Spinocerebellum
Vestibulocerebellum

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3
Q

Cerebrocerebellum

A
  • lateral cerebellar hemisphere
  • input directly from cortex
  • regulates and guides highly skilled movements (e.g. planning and execution of complex movements)
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4
Q

Spinocerebellum

A

Median (Vermis) and paramedian (more lateral) zone of hemisphere

  • input directly form spinal cord
  • paramedian zone: distal muscle movements
  • Vermis: movement of proximal muscles and eyes
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5
Q

Vestibulocerebellum

A
  • caudal inferior lobes (flocculus + nodulus)
  • input from vestibular nuclei in brainstem
  • regulates movement underlying posture & equilibrium + vestibulo-ocular reflex
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6
Q

Cerebellar Pedunles (pathways)

A

Superior cerebellar peduncles
Middle cerebellar peduncles
Inferior cerebellar peduncle

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7
Q

Superior cerebellar peduncles

A

Brachium conjunctivum

  • almost entirely efferent
  • deep cerebellar nuclei -> dorsal thalamus -> premotor & primary motor areas
  • deep cerebellar nuclei -> superior colliculus
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8
Q

Middle Cerebellar peduncles

A

Brachium pontis

  • afferent (contralateral)
  • most areas of cortex & superior colliculus -> cell bodies in pontine nuclei of ponts -> transverse pontine fibers cross over via middle cerebellar peduncles -> cerebellar cortex & deep nuclei
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9
Q

Inferior cerebellar peduncle

A

Restiform body

  • smallest pathway
  • afferent: from vestibular nuclei, spinal cord, tegmentum (stay ipsilateral)
  • efferent: to vestibular nuclei & reticular formation
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10
Q

Cerebellar Input

A
  • cortex via pontine to cerebrocerebellum (only contralateral)
  • spinal cord & medulla -> spinocerebellum (innervates by proprioceptive axons from lower & uper body parts)
  • trigeminal complex -> spinocerebellum (proprioceptive signals from face)
  • vestibular nuclei & axons of 8th cranial nerve -> vestibulocerebellum: (info from ear)
  • auditory & visual signals via brainstem to vermis
  • from inferior olives & locus creruleus (learning and memory function)
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11
Q

Cerebellar Output

A

To deep cerebellar nuclei:

  • dentate nucleus (cerebrocerebellum)
  • two interposed nuclei (paramedial)
  • fastigial nucleus (vermis)
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12
Q

Ascending Cerebellar Output

A

Cross at decussation of superior peduncle in midbrain then to thalamus & upper motor neurons in brainstem & cortex

  • > cerebrocerebellar pathways
  • > spinocerebellar pathways
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13
Q

Cerebrocerebellar pathways

A
  • for premotor & associational cortices of frontal lobe
  • > motor planning
  • feedback loops: to parvocellular red nucleus in midbrain -> inferior olives
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14
Q

Closed loops

A

Cerebrocerebellum sending projections back to same cortical (non-motor areas) from which its input signal originated in

  • > may influence coordination of non-motor programs
  • run in parallel to open loops
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15
Q

Open loops

A

input from multiple areas, output to motor cortices

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16
Q

Spinocerebellar Pathways

A

Directed to upper motor neurons for execution of movement:
Vermis -> inferior peduncle -> reticular formation & vestibular complex which give rise to tracts governing axial & proximal limb muscles

17
Q

Vestibulocerebellar pathway

A

Inferior peduncle -> vestibular complex: governs movement of eyes, head, neck, compensating for linear & rotational accelerations of the head

18
Q

Purkinje Cells

A

Destination of afferent pathways

  • huge outbranching dendrites; receive input from parallel fibers
  • inhibitory (GABA)
  • project to deep cerebellar nuclei to shape discharge patterns
19
Q

Indirect cerebellar input

A

Mossy fibers from various sources (cortex, brainstem, spinal cord) and synapse on deep cerebellar nuclei & granule cells
-granule cells give rise to parallel fibers

20
Q

Direct cerebellar input

A

Inferior olive -> climbing fibers that synapse on Purkinje cells and deep cerebellar nuclei

21
Q

Local circuit neurons

A

Modulate inhibitory output of Purkinje cells by inhibiting them after excitatory input from parallel fibers
-Basket cells & stellate cells inhibit purkinje cells (lateral inhibition)

22
Q

Golgi cells

A

receive input from parallel fibers and inhibit granule cells

23
Q

Long-term depression of climbing fibers

A

LTD in purkinje cells in response to parallel fiber inputs:

  • affects only parallel fibers active at same time as climbing fibers
  • internalization of AMPA receptors for glutamate (-> smaller EPSP)
  • weakens inhibitory loop increasing deep nuclei response
24
Q

Timing Hypothesis

A

Cerebellum critical for sensorimotor learning: generates predictions that are temporally precise

  • > cerebellum supplies precise timing needed for activating effectors
    e. g. airpuff experiment
25
Q

Forward Model

A

set of motor commands is transformed into prediction of their outcome in terms of sensory consequences of the move by the cerebellum

  • > predicts wheteehr motor program will achieve its goal before its carried out
  • > used to plan & control movement
26
Q

Inverse Model

A

Inverts information flow of forward model by inputting the desired goal of the movement

  • > back-calculating motor commands that are required
  • > disproven: TMS of cerebellum would affect whole movement, not the case
27
Q

Attenuation of self-produced tactile stimulation

A

Due to sensory predictions made by forward model

  • > right anterior cerebellar cortex selectively deactivated for self-produced tactile stimuli
  • > somatosensory & anterior cingulate cortex less activated by self-produced tactile stimulus
28
Q

Cerebellar Ataxia

A

jerky and imprecise movements

29
Q

Nystagmus

A

Difficulty of maintaining fixation in eyes -> drift from target, then jump back

30
Q

Dysdiadochokinesia

A

Difficulty performing rapid alternating movements

31
Q

Action/intention tremors

A

Over & undershooting of movements

32
Q

TMS cerebellar ataxia diagnosis

A

TMS can induce cerebellar inhibition of M1

  • > cerebellar ataxia: impaired cerebellar inhibition
  • > normal cerebellar inhibition with TMS: ataxia not originating from lesion to cerebellum

Functional Neuroanatomy (4 decks)

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