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. [Display omitted] •The superior colliculus exerts directional control on forelimb reaching movements•SClat-Vglut2 neurons show increased activity during and before reaching movements•Inactivation of SC during different reach phases preserves directional biases•SC and SNr work in coordination to implement directional control of reach accuracy Goal-oriented reaching necessitates precise regulation of multiple movement parameters. Chaterji et al. demonstrate that excitatory neurons in the lateral superior colliculus (SC) control the directional component of reach kinematics in concert with the substantia nigra pars reticulata, providing evidence for the direct contribution of the SC in skilled forelimb control.