Figure 1. Spatiotemporal organization of twitching.

(A) Time-lapse photographs, compiled from two sequential high-speed video frames, of a supine 8-day-old rat exhibiting discrete twitches of the left elbow (top) and right shoulder (bottom). Yellow arrows indicate direction of movement. The white dots are used for motion tracking of joint movements. (B) Spatiotemporal organization of twitching in an 8-day-old rat at three timescales. Each tick mark indicates the occurrence of a twitch in the right (red) or left (blue) forelimb at the shoulder, elbow, or wrist, as determined using high-speed video and motion tracking. For each joint, two movements are depicted: adduction and abduction for the shoulder and flexion and extension for the elbow and wrist (denoted by solid and dashed lines for each joint). Non-random distribution of twitching is evident at each timescale, especially at the two smaller timescales in which the “bouts-within-bouts” structure of twitching is most apparent. (C) Frequency distribution of inter-twitch intervals for P2 and P8 rats across shoulder, elbow, and wrist joints in the two forelimbs (pooled over >5000 intervals).