TY - JOUR T1 - A developmental transition in the sensory coding of limb kinematics in primary motor cortex JF - bioRxiv DO - 10.1101/2020.12.14.422707 SP - 2020.12.14.422707 AU - Ryan M. Glanz AU - James C. Dooley AU - Greta Sokoloff AU - Mark S. Blumberg Y1 - 2021/01/01 UR - http://biorxiv.org/content/early/2021/04/10/2020.12.14.422707.abstract N2 - Primary motor cortex (M1) undergoes protracted development in mammals, functioning initially as a sensory structure. Throughout the first postnatal week in rats, M1 is strongly activated by self-generated forelimb movements—especially by the twitches that occur during active sleep. Here, we quantify the kinematic features of forelimb movements to reveal receptive-field properties of individual units within the forelimb region of M1. At postnatal day (P) 8, nearly all units were strongly modulated by movement amplitude, especially during active sleep. By P12, only a minority of units continued to exhibit amplitude-tuning, regardless of behavioral state. At both ages, movement direction also modulated M1 activity, though to a lesser extent. Finally, at P12, M1 population-level activity became more sparse and decorrelated, along with a substantial alteration in the statistical distribution of M1 responses to limb movements. These findings reveal a transition toward a more complex and informationally rich representation of movement long before M1 develops its motor functionality.Competing Interest StatementThe authors have declared no competing interest. ER -