Meeting Abstract

37.5  Monday, Jan. 5  Nonlinear integration of proprioceptive inputs to the lamprey central pattern generator for locomotion TYTELL, E.D.*; COHEN, A.H.; Univ. of Maryland, College Park; Univ. of Maryland, College Park tytell@umd.edu

When animals move, they receive feedback from numerous proprioceptive sensors. These sensors relay information on body movement to the spinal cord and brain, which must then integrate all of the signals and produce an appropriate response. The lamprey central pattern generator (CPG) for locomotion is a well studied system for examining proprioception and its effect on the locomotory pattern. In the lamprey, much of the proprioceptive input comes from mechanosensory neurons called edge cells that are located in the spinal cord along its full length. The CPG receives these spatially distributed inputs, but it is not known how the timing and distribution of multiple inputs affects the swimming pattern. Many mathematical models assume that inputs are independent, that their effects sum linearly, and that they do not affect the swimming frequency. However, these assumptions have not been tested empirically. To examine how the CPG integrates multiple proprioceptive inputs, fictive swimming was induced in lamprey spinal cords. First, the spinal cord was bent at the rostral or caudal end to stimulate the edge cells. Changes in burst period, burst amplitude, and phase lags were assessed for several cycles after the stimulus. Then, three types of double stimuli were tested: (1) two stimuli at different locations simultaneously, (2) two stimuli at the same location with a time lag between them, and (3) two stimuli at different locations with a time lag. Preliminary results indicate that the effect of simultaneous stimuli at two locations may sum nonlinearly. Additionally, stimuli may shorten burst periods for several cycles after the stimulus, which may invalidate one of the assumptions underlying many mathematical models of the CPG.