Final Report Summary - MOTOR_DEV (Sensory feedback in the development of motor cortex: underlying physiological network mechanisms and its relation to epileptic discharges)
• Scientific summary
Integration of motor and somatosensory functions is a primary requirement for body movement control and exploration (Llinas, 2001). Motor and somatosensory systems develop and bind together to support sensorimotor integration (Arber, 2012) Early stages of sensorimotor system development are characterized by the occurrence of spontaneous movements. Whether and how these movements support coordination in developing sensorimotor circuits remains unknown, however.
Part I. Using translaminar recordings from the spinal cord of neonatal rats in vivo, we found highly correlated activity in sensory and motor zones, provided by movement-related bursts in motor zones that were followed by bursts in sensory zones, suggesting a potential involvement of sensory feedback and efferent copy. Deafferentation did not affect activity in motor zones and movements, but profoundly suppressed activity bursts in sensory lamina and resulted in almost complete sensorimotor uncoupling, implying a primary role of sensory feedback in sensorimotor integration. This was further supported by largely dissociated activity in sensory and motor zones observed in the isolated spinal cord preparation in vitro. Thus, sensory feedback resulting from spontaneous movements is instrumental for coordination of activity in developing sensorimotor spinal cord circuits.
Part II. Through simultaneous recordings of primary motor cortex (M1) activity and motor behavior in neonatal rats, we found so far that, over the first postnatal week, spontaneous hindlimb movements trigger spindle-bursts in the corresponding area of the contralateral M1. At these ages, epileptiform discharges, induced by local delivery of bicuculline, in M1 also were driven by spontaneous movements. From the second postnatal week, spontaneous movements and M1 spindle-bursts waned in parallel with the development of continuous background activity, and local bicuculline-induced M1 epileptiform discharges started driving contralateral hemiclonic jerks. Thus, during the first postnatal week, M1 operates essentially in a somatosensory mode, with sensory feedback resulting from spontaneous movements triggering topographic spindle-bursts that are potentially involved in the activity-dependent formation of sensorimotor circuits. Epileptiform discharges in M1 cortex during the neonatal period remain largely infraclinical.
Integration of motor and somatosensory functions is a primary requirement for body movement control and exploration (Llinas, 2001). Motor and somatosensory systems develop and bind together to support sensorimotor integration (Arber, 2012) Early stages of sensorimotor system development are characterized by the occurrence of spontaneous movements. Whether and how these movements support coordination in developing sensorimotor circuits remains unknown, however.
Part I. Using translaminar recordings from the spinal cord of neonatal rats in vivo, we found highly correlated activity in sensory and motor zones, provided by movement-related bursts in motor zones that were followed by bursts in sensory zones, suggesting a potential involvement of sensory feedback and efferent copy. Deafferentation did not affect activity in motor zones and movements, but profoundly suppressed activity bursts in sensory lamina and resulted in almost complete sensorimotor uncoupling, implying a primary role of sensory feedback in sensorimotor integration. This was further supported by largely dissociated activity in sensory and motor zones observed in the isolated spinal cord preparation in vitro. Thus, sensory feedback resulting from spontaneous movements is instrumental for coordination of activity in developing sensorimotor spinal cord circuits.
Part II. Through simultaneous recordings of primary motor cortex (M1) activity and motor behavior in neonatal rats, we found so far that, over the first postnatal week, spontaneous hindlimb movements trigger spindle-bursts in the corresponding area of the contralateral M1. At these ages, epileptiform discharges, induced by local delivery of bicuculline, in M1 also were driven by spontaneous movements. From the second postnatal week, spontaneous movements and M1 spindle-bursts waned in parallel with the development of continuous background activity, and local bicuculline-induced M1 epileptiform discharges started driving contralateral hemiclonic jerks. Thus, during the first postnatal week, M1 operates essentially in a somatosensory mode, with sensory feedback resulting from spontaneous movements triggering topographic spindle-bursts that are potentially involved in the activity-dependent formation of sensorimotor circuits. Epileptiform discharges in M1 cortex during the neonatal period remain largely infraclinical.