Coding of self and environment by Pacinian neurons in freely moving animals.

Pacinian corpuscle neurons are specialized low-threshold mechanoreceptors (LTMRs) that are exquisitely tuned to high-frequency vibration (∼40-1000 Hz) 1-5 . Although much is known about their tuning properties, it is unclear how Pacinians encode naturalistic behavior. Here, we developed a technique to record from Pacinian neurons and other LTMRs in awake, freely moving mice. We find that Pacinian LTMRs can robustly respond to self-generated vibrations caused by movement alone. Pacinians are highly active during a wide variety of natural behaviors, including grooming, digging, and climbing. Pacinians in the hindlimb are sensitive enough to be activated by forelimb- or upper-body-dominant behaviors. Strikingly, Pacinians can uniquely and reliably encode subtle vibrations of surfaces encountered by the animal, including low-amplitude vibrations initiated over two meters away. Finally, as a population, there is a broad range of Pacinian responses during natural behaviors and environmental vibrations, and an individual Pacinian's responsiveness is strongly dependent on its distinct sensitivity and frequency tuning. Thus, Pacinian corpuscle LTMRs, with their varying sensitivities, frequency tuning, and body distributions, collectively encode a wealth of vibro-tactile features of self-initiated movements and the environment.