Abstract:

To examine timing parallels between actual and imagined movement, the present study tested for 1/f noise in motor imagery (MI). Participants pointed and imagined pointing to a single target (Experiment 1), to targets of varied size (Experiment 2), and switched between pointing and grasping (Experiment 3). Experiment 1 showed comparable patterns of 1/f noise, or long-range correlation, in the timing of actual and imagined movement (i.e., similar scaling exponents). There was a tendency toward increased 1/f noise for both MI and motor performance with increased task difficulty in Experiment 2, perhaps reflecting adaptation to a more complex environment. Experiment 3 showed parallel attenuation of 1/f noise with task switching, perhaps reflecting discontinuity of mental set. As 1/f noise indicates positive correlation between early and later timing variability, the variability equivalence reflected in present results suggests that MI incorporates trial-to-trial error across a range of psychophysical constraints. This provides initial support for the notion that simulation and action involve similarly fine-grained timing processes, taking into account both cognitive and environmental parameters.