Behaviorally Selective Engagement of Short-Latency Effector Pathways by Motor Cortex

• Published in: Neuron (Cambridge, Mass.) Vol. 95; no. 3; pp. 683 - 696.e11
• Main Authors: Miri, Andrew, Warriner, Claire L., Seely, Jeffrey S., Elsayed, Gamaleldin F., Cunningham, John P., Churchland, Mark M., Jessell, Thomas M.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 02-08-2017; Elsevier Limited
• Subjects: Animal behavior; Animals; channelrhodopsin; Choice Behavior - physiology; Cortex (motor); Electrical stimuli; Electromyography; Electromyography - methods; Fitness equipment; Forelimb - physiology; Latency; Lesions; Male; Mice; motor cortex; Motor Cortex - physiology; Motor neurons; Motor Neurons - physiology; Motor task performance; mouse; Movement - physiology; Muscle function; neural dynamics; Neural Pathways - physiology; neural recording; Neurons; Optogenetics - methods; Perturbation methods; Stimulation; Synaptic Transmission - physiology; neural dynamics; mouse; motor cortex; channelrhodopsin; neural recording
• ISSN: 0896-6273; 1097-4199
• DOI: 10.1016/j.neuron.2017.06.042

Blocking motor cortical output with lesions or pharmacological inactivation has identified movements that require motor cortex. Yet, when and how motor cortex influences muscle activity during movement execution remains unresolved. We addressed this ambiguity using measurement and perturbation of motor cortical activity together with electromyography in mice during two forelimb movements that differ in their requirement for cortical involvement. Rapid optogenetic silencing and electrical stimulation indicated that short-latency pathways linking motor cortex with spinal motor neurons are selectively activated during one behavior. Analysis of motor cortical activity revealed a dramatic change between behaviors in the coordination of firing patterns across neurons that could account for this differential influence. Thus, our results suggest that changes in motor cortical output patterns enable a behaviorally selective engagement of short-latency effector pathways. The model of motor cortical influence implied by our findings helps reconcile previous observations on the function of motor cortex.
•In mice, motor cortex is required for a trained forelimb task, but not walking•Motor cortex activates short-latency effector pathways only during the trained task•Distinct weighted sums of motor cortical firing patterns vary strongly in each task•This change could permit motor cortex to engage short-latency pathways differentially
Miri et al. measured and perturbed motor cortical activity during simultaneous electromyography to reveal behavioral selectivity in the engagement of short-latency effector pathways by motor cortex. Changes in the correlation among output firing patterns appear to mediate this selectivity.