256 SECTION III Central & Peripheral Neurophysiology
and axon hillock of each Purkinje cell they innervate. Stellate
cells are similar to the basket cells but more superficial in
location. Golgi cells are located in the granular layer (Figure
16–14). Their dendrites, which project into the molecular
layer, receive input from the parallel fibers (Figure 16–15).
Their cell bodies receive input via collaterals from the incom-
ing mossy fibers and the Purkinje cells. Their axons project to
the dendrites of the granule cells.
The two main inputs to the cerebellar cortex are climbing
fibers and mossy fibers. Both are excitatory (Figure 16–15).
The climbing fibers come from a single source, the inferior
olivary nuclei. Each projects to the primary dendrites of a
Purkinje cell, around which it entwines like a climbing plant.
Proprioceptive input to the inferior olivary nuclei comes from
all over the body. On the other hand, the mossy fibers provide
direct proprioceptive input from all parts of the body plus
input from the cerebral cortex via the pontine nuclei to the
cerebellar cortex. They end on the dendrites of granule cells in
complex synaptic groupings called glomeruli. The glomeruli
also contain the inhibitory endings of the Golgi cells men-
tioned above.
The fundamental circuits of the cerebellar cortex are thus rel-
atively simple (Figure 16–15). Climbing fiber inputs exert a
strong excitatory effect on single Purkinje cells, whereas mossy
FIGURE 16–14 Location and structure of five neuronal types in the cerebellar cortex. Drawings are based on Golgi-stained prepara-
tions. Purkinje cells (1) have processes aligned in one plane; their axons are the only output from the cerebellum. Axons of granule cells (4) traverse
and make connections with Purkinje cell processes in molecular layer. Golgi (2), basket (3), and stellate (5) cells have characteristic positions, shapes,
branching patterns, and synaptic connections. (Reproduced with permission from Kuffler SW, Nicholls JG, Martin AR: From Neuron to Brain, 2nd ed. Sinauer, 1984.)
1 23455 Stellate
cell(^1) Purkinje
cell
2 Golgi
cell
3 Basket
cell
4 Granule
cell
Axon
Axons
Axon
Molecular
layer
Purkinje
layer
Granular
layer
Parallel fibers:
Axons of granule
cells
FIGURE 16–15 Diagram of neural connections in the
cerebellum. Plus (+) and minus (–) signs indicate whether endings are
excitatory or inhibitory. BC, basket cell; GC, Golgi cell; GR, granule cell;
NC, cell in deep nucleus; PC, Purkinje cell. Note that PCs and BCs are in-
hibitory. The connections of the stellate cells, which are not shown, are
similar to those of the basket cells, except that they end for the most
part on Purkinje cell dendrites.
Other
inputs
- Mossy fiber
Climbing +
fiber
−
−
−
Parallel fiber
PC
BC
GR
GC
NC
Cerebellar
cortex
Deep
nuclei