The superior colliculus directs goal-oriented forelimb movements

Skilled forelimb control is essential for daily living, yet our understanding of its neural mechanisms, although extensive, remains incomplete. Here, we present evidence that the superior colliculus (SC), a major midbrain structure, is necessary for accurate forelimb reaching in mice. We found that neurons in the lateral SC are active during goal-directed reaching, and by employing chemogenetic and phase-specific optogenetic silencing of these neurons, we show that the SC causally facilitates reach accuracy. Anatomical studies identified the deep cerebellar nuclei and substantia nigra pars reticulata as sources of inputs to the SC, while functional studies revealed a role for nigrotectal, but not cerebellotectal, neurons in controlling reach endpoints. Silencing the nigrotectal pathway caused paw deviations opposite to those seen with SC silencing, emphasizing the coordinated role of the substantia nigra and SC in regulating optimal reaching. Together, these findings establish the SC as a crucial regulator of skilled forelimb control.