Fig. 1

Signal formation by chained GABAergic interneurons in the cerebellar cortex. Left panel: Schematic diagram of the cerebellar cortex. Arrows: signal flows in the cerebellar cortex. White cells: excitatory neurons, black cells: inhibitory neurons. (+); excitatory synapses, (−); inhibitory synapses, MF; mossy fibers, GC; granule cells, PF; parallel fibers, Inhibitory IN; inhibitory interneurons, PC; Purkinje cells; Deep Cerebellar Nuclei; deep cerebellar nuclei neurons. Right panel: Schematic diagram of activities of inhibitory interneurons, Purkinje cells, and deep cerebellar nuclei neurons. MF inputs activate granule cells, which in turn elicit two modes, inhibitory mode and disinhibitory mode. Inhibitory mode; Purkinje cells inhibit activities of the output signals conveyed by cerebellar nucleus neurons, which suppresses adventitious movements. Disinhibitory mode; Inhibition of Purkinje cells by inhibitory interneurons releases this inhibition on outputs, which facilitates the execution of aimed movements. Since this inhibitory/disinhibitory mode, which is formed by the chained GABAergic neurons, is an essential feature for cerebellar circuitry. A decrease in GABA release impairs signals formation in the cerebellum, causing cerebellar ataxia through abnormal motoneuronal commands