Static and phasic cross-talk effects in discrete bimanual reversal movements

The authors examined the hypothesis that the phasic and the static cross-talk effects found in bimanual movements with different target amplitudes originate at different functional levels of motor control, which implies that the effects can be dissociated experimentally. When the difference between the short and the long amplitudes assigned to the 2 hands of 12 participants was decreased, the static effect disappeared, In contrast, the phasic effect, which can be observed only at short preparation intervals, did not disappear; although it became smaller in absolute terms, in relative terms it did not. In addition, the authors compared the time course of amplitude variability and examined the correlation between left hand and right hand amplitudes. The disappearance of the phasic amplitude assimilation at increasing preparation intervals turned out to be delayed relative to the decline of the correlation between amplitudes. That finding suggests that the assimilation of mean amplitudes and the correlation between left hand and right hand amplitudes are not fully equivalent indicators of intermanual interactions, but may indicate different kinds of inter-limb coupling.