[Relations between the basal ganglia and the thalamus of the primate. New morphologic data. New physiopathologic interpretations].

Considerable progress has been made over the last few years in our knowledge of the thalamus and basal ganglia and their relationships to the cerebral cortex. More detailed topographic studies in the macaque have demonstrated the separation, in the lateral region of the thalamus, between afferent cerebellar and basal ganglia territories. These territories fail to correlate with the subdivision between ventral and dorsal elements or the limits of a single cytoarchitectonic nucleus. The cerebellar territory corresponds to VIL (or VPLo) which projects towards the primary cortex, and to VIM (or area X) and DI (or VLc) which project towards premotor cortex. The nigral (and tectal) territory corresponds to VOM (or VAmc) and to some parts of the medial nucleus and projects mainly towards the oculomotor area, supplementary motor area and prefrontal cortex. In return, the oculomotor area and substantia nigra project towards the colliculus superior. Several thalamic nuclei constitute the pallidal territory: VOL (or VLo) projects mainly towards supplementary motor area, LPo (or VApc) and Do towards the prefrontal cortex. The median center, which receives afferents from pallidum and motor cortex, projects towards the striatum but also the motor cortex. The parafascicular nucleus projects towards the striatum and premotor cortex. It is still not possible to transpose data acquired in the macaque to man, but functional reinterpretations are possible. A system which involves the median pallidum, VOL and supplementary motor area could control motor initiative and flow of movement. A second system, involving the substantia nigra, colliculus superior, thalamic relay and oculomotor area could control posture. The pallidum and substantia nigra, anterior part of lateral mass, medial nucleus and prefrontal cortex could elaborate motor programmes.