Cerebellum: The sequel

Cerebellar afferent fibers

climbing fibers, mossy fibers

Climbing fibers are highly

specific

climbing fibers are highly

convergent

climbing fibers convey

event-related information (error)

mossy fibers are highly

convergent

mossy fibers convey

magnitude and duration of sensory information

simple spikes are produced by

mossy fiber input

complex spikes are produced by

climbing fiber synapses

Cerebellar efferent fibers

purkinje neurons

purkinje neurons receive

substantial afferent input

only source of cerebellar cortical output

purkinje neurons

purkinje neurons have an

inhibitory influence on deep cerebellar nuclei

Cerebellar interneurons

stellate cells, basket cells, golgi cells, parallel fibers

Direct Inhibition Interneurons

stellate cells and basket cells

indirect inhibition interneurons

golgi cells

excitatory interneurons

parallel fibers

parallel fibers are

extensions of granule cells

interneurons

modulate the activity of cerebellar cortical output via direct or indirect connections with purkinje neurons

Cerebellar circuits

principle, interneuron, comprehensive

cerebellar circuitry allows for

checks and balances on cerebellar output

principle circuit

excitation of purkinje neurons via mossy (indirect) and climbing fibers (direct)

Interneuron circuit

inhibition of purkinje neurons via basket and stellate cells (direct) and golgi cells (indirect)

Comprehensive circuit

excitation of deep cerebellar nuclei via mossy and climbing fibers

Recurrent loops involve

golgi cells within the cerebellar cortex and the inferior olive outside the cerebellum

Deep cerebellar nuclei activity is regulated

by three mechanisms

Three regulatory mechanisms

• excitatory input from afferent fiber collaterals

• Inhibitory inputs from purkinje neurons activated by mossy fiber connections

  • inhibitory inputs from purkinje neurons activated by climbing fiber connections