Spontaneous activity synchronizes whisker-related sensorimotor networks prior to their maturation in the developing rat cortex

A prominent feature of the cortical systems controlling the whiskers in the adult rodent is tight coupling between sensory and motor systems. Stimulation of the whiskers evokes activation of discrete motor regions of cortex shortly after activation of the sensory cortex. To explore the factors that direct the development of sensorimotor functional connectivity, we recorded spontaneous and whisker-evoked cortical activity using voltage-sensitive imaging over a large (7X7 mm) craniotomy in postnatal rats (day 5-12) under anesthesia. We found that spontaneous bursts of activity in the barrel cortex were correlated predominantly with activity in motor (anterio-medial) cortex, at ages before whisker stimulation evoked activation in this area. Intracortical microstimulation and anatomical tracing experiments confirmed there were no functional or anatomical intracortical sensorimotor connections. We interpret these results as evidence that the spontaneous patterns of activity in the cortex synchronize functionally related regions of the brain prior to their maturation. Author Contributions D.A.M, T.H.M., and M.H.M. designed the study. D.A.M, and M.H.M performed the experiments and analyzed the data and wrote the manuscript, which all authors commented on and edited. T.H.M. and M.H.M. supervised the study.