Cell-class-specific orofacial motor maps in mouse neocortex

Cortical motor maps represent fundamental organizing principles for voluntary motor control,¹ yet their underlying structure remains poorly understood, including regions of sensory^2,3 and parietal cortex,⁴ as well as the classical frontal motor cortex. To understand how anatomically distinct cortical areas are organized into functional units for controlling movements, here, we refined cortical motor maps by selectively stimulating genetically defined subpopulations of excitatory neurons. Surprisingly, we found spatially segregated modules in orofacial motor maps by optogenetically stimulating different classes of cortical excitatory neurons. The overall motor map for jaw opening revealed by stimulating all classes of excitatory neurons spanned the anterior lateral cortex broadly. By contrast, the jaw-opening motor maps of specific genetically defined cell classes were focalized either in primary motor, secondary motor, or primary somatosensory areas within the overall jaw-opening motor map of all excitatory neurons, demonstrating cell-class-specific motor map modules. Simultaneous wide-field calcium imaging revealed activity propagation from optically stimulated motor map modules to the primary motor area correlating with movement vigor. The motor map modules were largely stable across lick motor learning with important exceptions indicating cell-class-specific expansion into other module zones. Our data suggest that distinct cell-class-specific modules interacting across sensorimotor cortices might contribute to controlling orofacial movement.