Neuroanatomy Lecture 23

Cerebellar Circuitry

Folia Contain…

the circuitry of the cerebellar cortex

3 Layers of the Cerebellar Cortex

molecular (outermost), purkinje (middle), granule (innermost)

Purkinje Cells

inhibitory projection neurons, create a large, flat dendritic tree, parallel to one another along folia, sole output of the cerebellar cortex

Granule Cells

excitatory neurons that cause depolarization, need many of these small cells to affect many PKJ, innermost layer of the cerebellar cortex, axons are parallel fibers which run along the folia, form weak synapses on purkinje neurons because they are way out on the dendrites so have to travel far, project across the length of parallel fibers

Golgi Cells

cell bodies are in the granule cell layer, inhibitory, excited by parallel fibers, provide feedback inhibition to the granule cell that initially activated it, inhibition gives a tiny window

Basket Cells

cell bodies are in the molecular layer, inhibitory, excited by parallel fibers, provide feedforward inhibition to Purkinje cells so no loop

Climbing Fibers

provide input from the inferior olivary nuclei, and send excitatory projections to PKJ cells and deep cerebellar nuclei, can have large effect on PKJ, synapse close to apical dendrite and big and near cell body so very strong influence

Mossy Fibers

provide excitatory input from vestibular nuclei, spinal cord, trigeminal brainstem nuclei, pontine nuclei and send projections to deep cerebellar nuclei and granule cells

Climbing Fiber Inputs

closer to cell body, strong excitatory synapses, trigger complex spikes in PKJ cells, multiple action potentials

Mossy Fiber/Parallel Fiber Inputs

weak excitatory synapses, many together trigger simple spikes in PKJ cells, action potential outside cell

Parallel Fibers

run along the top and connect to granule cells, give input to PKJ but it is weak, axons branch

Only Output from the Cerebellum

deep cerebellar nuclei

Only Output from Cerebellar Cortex

purkinje fibers

Purkinje Cell Impairment Symptoms

ataxia, impaired gait and balance, slurred speech, dysmetria, dysdiadochkinesia, cognitive impairment, chorea (dance, Huntington’s), dystonia

Motor Learning

modifying motor programs with practice to improve the effectiveness and efficiency of movements, adapting motor output based on sensory feedback from movement, can learn opposite skills that don’t mess with each other, cerebellum good at this, damage means can’t learn new things

What does the cerebellum do?

learn to associate two stimuli together, coordination of movement, motor learning, classical conditioning, language, higher cognitive functions?, regulation of emotion?, psychiatric illness?