Transcript and by climbing fibers

Lecture 15:
Cerebellum
Vermis
Peduncles
Hemisphere
Fastigial
nuclei
Interposed
nucleus
(emboliform
and globose
nuclei)
Dentate
nucleus
The cerebellum consists of
two hemispheres and a
medial area called the
vermis. The cerebellum is
connected to other neural
structures by three pairs
of peduncles. The figure
shows a dorsal view of the
cerebellum, and the
peduncles and cerebellar
nuclei are obscured
(shown by black areas).
Cerebellar Lobes
Primary fissure
Anterior lobe
Posterior
lobe
Posteriorlateral fissure
Flocculus
Nodulus
Flocculonodular lobe
The cerebellum is divided into three lobes: the anterior
lobe, the posterior lobe, and the flocculonodular lobe.
Somatotopical Projections
on the Cerebellum
Neurons of the Cerebellum
Basket cell
Stellate cell
Molecular layer
Purkinje cell layer
Golgi cell
Granular layer
Granule cell
White matter
Climbing fiber
Output (to cerebellar
nuclei and then to
thalamus, brain stem,
and vestibular nuclei)
Mossy
fiber
The cerebellar cortex
consists of three layers and
five types of neurons.
Inputs to the cerebellum
are carried by mossy
fibers (from the inferior
olive) and by climbing
fibers (from pontine
nuclei, the vestibular
system, and the spinal
cord). The only output
system of the cerebellum is
the axons of Purkinje cells.
Cerebellar Neurons
A Glomerulum
Golgi cell axon
Rosette
Mossy
fiber
Granule cell dendrites
A single glomerulum consists of an incoming mossy fiber,
clusters of small dendrites (called rosettes) from a few dozen
granule cells, and the axons of the Golgi cells.
Inputs Into the Cerebellum
Granule cells
Purkinje cells
Mossy fibers
(spinocerebellar tract
and brain stem nuclei)
Climbing fibers (inferior olive)
Excitatory inputs to the cerebellum are provided by mossy fibers and
climbing fibers. The mossy fibers originate in the spinocerebellar
tract and in brain stem nuclei; they excite granule cells. The climbing
fibers originate in the medulla (the inferior olive); they make synapses
on Purkinje cells.
Simple and Complex Spikes
Simple
spike
Complex spike
In response to a single excitatory stimulus, a Purkinje cell
may generate
 a single action potential (a simple spike, in response to
mossy fiber input), or
 a larger action potential, followed by a few smaller action
potentials (a complex spike, in response to a signal from
climbing fibers).
Wiring of the Cerebellum
Distant
Purkinje cells
Basket cells
Parallel fibers
Purkinje cells
Golgi cells
Climbing
fiber
Stellate cells
Granular cells
Glomeruli
Mossy
fibers
Stellate cells make
inhibitory synapses on the
dendrites of Purkinje cells.
Parallel fibers activate
Purkinje cells, basket cells,
stellate cells, and Golgi cells.
Basket cells inhibit
relatively distant Purkinje
cells. Golgi cells inhibit
granular cells, decreasing
their response to mossy
fibers.
Neuronal Population Vectors of the Purkinje
Cells and Neurons in the Cerebellar Nuclei
Cerebellar Memory?
Climbing fibers
Parallel
fibers
Purkinje
cell
If an action potential in a
climbing fiber and
another action potential in
a parallel fiber arrive
simultaneously at a
Purkinje cell, the cell may
“remember” this
event with the help of a
chemical mechanism,
changing the synaptic
efficacy.