Fig. 1.

Simplified diagram of the cortico-cerebello-thalamocortical and cortico-basal ganglia-thalamocortical circuitry based on data derived from tracing studies in monkeys. The cerebellar nuclei project to the motor thalamus via the fasciculus cerebellothalamicus (fct), with primary target in the VLp, but also in VLa and VM (projections to medial thalamic nuclei are not included in the schema). Efferent connections of the GPi to the thalamus course through the ansa lenticularis (al) and the fasciculus lenticularis (fl), and the two fibre bulks merge to form the fasciculus thalamicus (ft) which projects primarily to the VLa, VApc, and VM nuclei, with only minor projections to the VLp (projections to the intralaminar nuclei are not shown). Equivalent Hassler’s nomenclature (Hassler 1982) for thalamic nuclei is also indicated. Connections to the thalamus and cortex are represented with different thicknesses according to their relative density and by different gradients in the thalamus. The two major motor pathways are also represented by different colors for clarity. See list of abbreviations