Abstract
To control reaching, the nervous system must generate large changes in muscle activation to drive the limb toward the target, and must also make smaller adjustments for precise and accurate behavior. Motor cortex controls the arm through projections to diverse targets across the central nervous system, but it has been challenging to identify the roles of cortical projections to specific targets. Here, we selectively disrupt cortico-cerebellar communication in the mouse by optogenetically stimulating the pontine nuclei in a cued reaching task. This perturbation did not typically block movement initiation, but degraded the precision, accuracy, duration, or success rate of the movement. Correspondingly, cerebellar and cortical activity during movement were largely preserved, but differences in hand velocity between control and stimulation conditions predicted from neural activity were correlated with observed velocity differences. These results suggest that while the total output of motor cortex drives reaching, the cortico-cerebellar loop makes small adjustments that contribute to the successful execution of this dexterous movement.
Highlights
The integration of ascending signals from the periphery with descending signals from higher brain regions is a widespread motif in the central nervous system
We found that the activity of pontine nuclei (PN) neurons was modulated both by movement and by non-motor events, and that disruption of PN function degraded task performance and altered cortical activity patterns
The PN are the major source of descending input to cerebellum, little is known about the activity of PN neurons during behavior
Summary
The integration of ascending signals from the periphery with descending signals from higher brain regions is a widespread motif in the central nervous system. The cerebellum, for instance, receives information from nearly every sensory modality, and ascending pathways carrying vestibular (Barmack, 2003), cutaneous (Bower and Woolston, 1983), proprioceptive (Bosco and Poppele, 2001), and visual (Stone and Lisberger, 1990) stimuli have been studied in detail. These sensory inputs often overlap with inputs from the pontine nuclei (PN) carrying descending information from higher brain areas such as cerebral cortex (Huang et al, 2013). The pontine nuclei have been estimated to be the source of over half of the mossy fiber inputs to the cerebellum
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