| Popis: |
Motor cortex is a key node in the forebrain circuits that enable flexible control of limb movements. The influence of motor cortex on movement execution is primarily carried by either pyramidal tract neurons (PT), which project directly to the brainstem and spinal cord, or intratelencephalic neurons (IT), which project within the forebrain. The logic of the interplay between these cell types and their relative contribution to the coordination and scaling of forelimb movements remains unclear. Here we combine large-scale neural recordings across all layers of motor cortex with cell-type specific perturbations in a cortex-dependent mouse behavior: kinematically-variable manipulation of a joystick. Our data demonstrate that descending neocortical motor commands are distributed across projection cell classes. IT neuron activity, in comparison to PT neurons, carries a larger fraction of information about gross movement kinematics. We find that forelimb movements are robust to optogenetic silencing of PT output, but substantially impaired by silencing Layer 5a IT projection neurons. Dorsal striatum is the unique extracortical integration point for IT and PT output pathways and its activity was more dependent upon IT input than PT input during movement execution. These data indicate that forebrain extrapyramidal pathways can be critical for regulating kinematics of motor skills. |
