Timings of attentional switching to perturbation and postural preparation during transient forward or backward floor translation.

Background: Relationships between the timings of attentional switching and postural preparation were investigated using a choice-reaction paradigm with transient floor translation (S2), with the direction indicated by a warning auditory signal (S1).

Methods: Thirteen healthy young adults participated in this study. S2 started 2 s after S1 onset while standing on the platform. The platform moved forward when S1 was a high tone, and backward when S1 was a low tone. In the S1-S2 period, attentional switching was evaluated by P3 component of event-related potential.

Results: A shift in the center of pressure in the anteroposterior direction (CoPap) or a continuous increase in postural muscle activation toward S2 was recognized as postural preparation. Changes in postural muscle activation were found just before the CoPap shift. P3 was observed about 250-650 ms after S1. Onset of postural preparation was significantly later (about 200 ms) than latency of P3 (p < 0.001) and correlated strongly with P3 latency (forward: r = 0.81, backward: r = 0.74, p < 0.01).

Conclusion: Postural preparation for S2 was demonstrated to start after attentional switching from S1 to S2.