For quantitative video analysis, video records were captured by a frame-grabber board in a MacIntosh IIx computer under the control of the public domain software program ‘ColorImage’, which is an enhancement of the ‘NIH Image’ program [2,3]. Individual frames were re-
trieved serially and displayed on an AppleColor 6403480 monitor for quantitative analysis. The CED Spike2 soft-ware program was used to analyze EMG activity.