RT Journal Article SR Electronic T1 Distribution of Networks Generating and Coordinating Locomotor Activity in the Neonatal Rat Spinal Cord In Vitro: A Lesion Study JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 5777 OP 5794 DO 10.1523/JNEUROSCI.16-18-05777.1996 VO 16 IS 18 A1 Kjaerulff, Ole A1 Kiehn, Ole YR 1996 UL http://www.jneurosci.org/content/16/18/5777.abstract AB The isolated spinal cord of the newborn rat contains networks that are able to create a patterned motor output resembling normal locomotor movements. In this study, we sought to localize the regions of primary importance for rhythm and pattern generation using specific mechanical lesions. We used ventral root recordings to monitor neuronal activity and tested the ability of various isolated parts of the caudal thoracic-lumbar cord to generate rhythmic bursting in a combination of 5-HT and NMDA. In addition, pathways mediating left/right and rostrocaudal burst alternation were localized. We found that the isolated ventral third of the spinal cord can generate normally coordinated rhythmic activity, whereas lateral fragments resulting from sagittal sections showed little or no rhythmogenic capability compared with intact control preparations. The ability to generate fast and regular rhythmic activity decreased in the caudal direction, but the rhythm-generating network was found to be distributed over the entire lumbar region and to extend into the caudal thoracic region. The pathways mediating left/right alternation exist primarily in the ventral commissure. As with the rhythmogenic ability, these pathways were distributed along the lumbar enlargement. Both lateral and ventral funiculi were sufficient to coordinate activity in the rostral and caudal regions. We conclude that the networks organizing locomotor-related activity in the spinal cord of the newborn rat are distributed.