Using scanning trials to assess intrinsic coordination dynamics.

Bimanual 1:1 coordination patterns other than in-phase (0 degrees ) and anti-phase (180 degrees ) have proven difficult to perform even with extended practice. The difficulty has been attributed to phase attraction that draws the coordination between the limbs towards the bimanual patterns of in-phase and anti-phase and variability associated with the activation of non-homologous muscles via crossed and uncrossed cortical pathways. We found participants could very effectively produce a large range of supposedly unstable coordination patterns (between 0 degrees and 180 degrees in 30 degrees increments) after only 3 min of practice when integrated feedback (Lissajous plots) was provided and other perceptual and attentional distractions were minimized. These findings clearly indicate that the perception-action system is fully capable of producing a wide range of bimanual coordination patterns and that the reason for the failure to produce these patterns in previous experiments reside in the perceptual information and attentional requirements typically found in experimental testing environments.