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Impact of movement and movement-related feedback on the lamprey central pattern generator for locomotion

Li Guan, Tim Kiemel and Avis H. Cohen^*

Department of Biology, University of Maryland, College Park, MD 20742, USA

View larger version (13K): [in a new window]   Fig. 1. Movement of a typical muscle preparation. The body is prepared by removing the head, viscera and a small portion of the dorsal musculature, and the skin is peeled away. EMG electrodes are inserted into muscles separated by approximately 15 segments. A small pin inserted through the notochord stabilizes lateral movement, but allows full rotation. Images were recorded on film at 15framess-1, with every fifth frame illustrated. To construct the figure, outlines of the preparation in a selected single frame were used to form the shapes. One cycle is illustrated. Lines of equal length are drawn vertically from the pinned end for each image with the lines originating from the pin position.

View larger version (26K): [in a new window]   Fig. 2. Results from the eight individual animals with intact spinal cords and rostrally pinned that were successfully tested in both conditions: trunk with muscle (Muscle) and isolated spinal cord and notochord (Cord). Each symbol represents the same animal in all graphs. (A) , the average of the rostral and caudal bursting frequencies. In cases in which the rostral and caudal outputs had different frequencies, the average of the two frequencies is plotted. (B) /, the rostral/caudal frequency ratio. (C) /n, the phase lag per segment between rostral and caudal outputs. (D) ß, the coupling strength parameter describing the functional coupling strength between rostral and caudal recording locations. The value ß=0 corresponds to no coupling, and the value ß=1 corresponds to infinite strength coupling. Error bars represent approximate 95% confidence intervals. In one case (open circles in the muscle condition), we were unable to compute confidence intervals because ß=1.

View larger version (21K): [in a new window]   Fig. 3. Means across all animals; values are means ± S.E.M. Intact spinal cords are designated with filled symbols (N=8; summary of data from Fig.2) and hemisected spinal cords with open symbols (N=7; summary of data from Fig.5). Other details as in Fig.2.

View larger version (27K): [in a new window]   Fig. 4. EMG recordings from a single animal under three conditions. (A) Intact animal swimming. (B) Trunk with muscle and spinal cord with two staggered hemisections. (C) Isolated spinal cord with two staggered hemisections. Values for this animal are represented by the filled squares in Fig.5. See text for further details. Ros, rostral; Cau, caudal.

View larger version (28K): [in a new window]   Fig. 5. Results from individual hemisected animals. A–D are as in Fig.2. (E) , the ascending fraction of coupling strength. If >0.5, ascending strength is greater than descending strength; if <0.5, ascending strength is less than descending strength. Error bars represent approximate 95% confidence intervals (N=7). In two cases (open squares and filled diamonds in the muscle condition), we were unable to compute confidence intervals because ß=1.