Population reconstruction of the locomotor cycle from interneuron activityin the mammalian spinal cord

Lesion studies have shown that neuronal networks in the ventromedial region s of the neonatal rat spinal cord are critical for the production of locomo tion. We examined whether the locomotor cycle could be accurately predicted based on the activity recorded in a population of spinal interneurons loca ted in these regions during pharmacologically induced locomotion. We used a Bayesian probabilistic reconstruction procedure to predict the most likely phase of locomotion given the observed activity in the neuronal population . The population reconstruction was able to predict the correct locomotor p hase with high accuracy using a relatively small number of neurons. This re sult demonstrates that although the spike activity of individual spinal int erneurons in the ventromedial region is weak and varies from cycle to cycle , the locomotor phase can be accurately predicted when information from the population is combined. This result is consistent with the proposed involv ement of interneurons within these regions of the spinal cord in the produc tion of locomotion.