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Fig. 1 | Cerebellum & Ataxias

Fig. 1

From: Overlooked Holmes’ clinical signs: reevaluation by recent physiological findings

Fig. 1

Relationship between breakdown of two modes of dentate nucleus cell (DNC) output and asthenia (top) and adventitious movements (bottom). Asthenia (top) is the consequence of breakdown of the Indirect mode while Adventitious movements (bottom) is the result of breakdown of the Direct mode. The diagram provides a summary of the functional organization of the cerebellum (Ishikawa et al. [5]). In the cerebellar cortex, mossy fiber (MF) inputs (INPUT) are relayed by granule cells (GCs) and processed through two parallel but different pathways, an indirect pathway (Indirect) and a direct pathway (Direct). In the indirect pathway (top), parallel fiber (PF) inputs activate interneurons (INs) that suppress PCs. Because PC activity provides tonic suppression of DNCs, suppression of PC activity facilitates DNCs through disinhibition (OUTPUT↑). Breakdown of this output mode leads to a decrease in facilitatory output, resulting in Asthenia. In the direct pathway (bottom), PF inputs excite PCs directly. Because PCs are inhibitory, their activation suppresses the DNCs (OUTPUT↓). Breakdown of this output mode leads to a decrease in suppression, resulting in Adventitious movements. CF: climbing fiber. (+): excitatory synapses, (−): inhibitory synapses

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