Intersegmental Interactions Give Rise to a Global Network

KEARNEY, GRACIELA; RADICE, MARTINA; MERLINSKY, AGUSTÍN SANCHEZ; SZCZUPAK, LIDIA

Frontiers in Neural Circuits

Frontiers Media SA

Lugar: Lausanne; Año: 2022 vol. 16

Animal motor behaviors require the coordination of different body segments. Thus theactivity of the networks that control each segment, which are distributed along the nervecord, should be adequately matched in time. This temporal organization may dependon signals originated in the brain, the periphery or other segments. Here we evaluatethe role of intersegmental interactions. Because of the relatively regular anatomy ofleeches, the study of intersegmental coordination in these animals restricts the analysisto interactions among iterated units. We focused on crawling, a rhythmic locomotivebehavior through which leeches move on solid ground. The motor pattern was studiedex vivo, in isolated ganglia and chains of three ganglia, and in vivo. Fictive crawlingex vivo (crawling) displayed rhythmic characteristics similar to those observed in vivo.Within the three-ganglion chains the motor output presented an anterior-posterior order,revealing the existence of a coordination mechanism that occurred in the absence ofbrain or peripheral signals. An experimental perturbation that reversibly abolished themotor pattern in isolated ganglia produced only a marginal effect on the motor activityrecorded in three-ganglion chains. Therefore, the segmental central pattern generatorspresent in each ganglion of the chain lost the autonomy observed in isolated ganglia,and constituted a global network that reduced the degrees of freedom of the system.However, the intersegmental phase lag in the three-ganglion chains was markedly longerthan in vivo. This work suggests that intersegmental interactions operate as a backboneof correlated motor activity, but additional signals are required to enhance and speedcoordination in the animal.