Vibrissa myoclonus (rhythmic retractions) driven by resonance of excitatory networks in motor cortex.

Rodents use rhythmic vibrissae movements to sense the environment. It is currently unclear whether intrinsic activity in the vibrissa motor cortex (vMI) is capable of driving vibrissa movements on a cycle-by-cycle basis. Disinhibition of vMI results in the occurrence of spontaneous 5- to 15-Hz synchronized oscillations. In behaving rats, this synchronous resonance of vMI is shown here to drive contralateral vibrissa movements that are phase-locked to each cycle of the oscillation. In contrast to active whisking during sensing, which consists of active protractions, the vibrissa movements produced by vMI oscillations consisted of rhythmic retractions. The results demonstrate that rhythmic motor cortex output is capable of driving vibrissa movements on a cycle-by-cycle basis. Such motor output may be primarily expressed during abnormal states such as those related to cortical myoclonous, tremors, and cortical seizures.