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Abstract:
In order to rapdily and accurately interact with the world, we need to perceive the consequences of our actions. It should not be surprising, then, that delaying the consequences of our actions, or delaying feedback about our actions, impairs performance on a wide range of tasks. We have recently shown that a few minutes exposure to delayed visual feedback induces sensorimotor temporal adaptation, returning performance to near normal levels. While visual feedback plays a large role in many tasks, there are some tasks for which vestibular perception is more critical. Here, we examine whether adaptation to delayed vestibular feedback is possible. To test for vestibular temporal adaptation, subjects were placed on a motion platform and were asked to perform a stabilization task. The task was similar to balancing a rod on the tip of your finger. Specifically, the platform acted as if it were on the end of an inverted pendulum. Subjects moved the platform by applying an acceleration to it via a joystick. The experiment was divided into 3 sections. During the Baseline section, which lasted 5 minutes, subjects performed the task with immediate vestibular feedback. They then were presented with a Training section, which consisted of 4 sessions (5 minutes each) during which vestibular feedback was delayed by 500 ms. Finally, subjects performance on the task with immediate feedback was remeasured during a 2 minute Post-test. The more difficulty one has in stabilizing the platform the more it will oscillate, increasing the variablilty in the platform's position and orientation. Accordingly, positional variance served as the primary measure of the subjects' performance. Subjects did rather well in the Baseline section (average standard deviation of platform tilt was 1.37 degrees). The introduction of the delay greatly impaired performance (8.81 degrees standard deviation in the 1st Training session), but performance rapidly showed significant improvement (5.59 degrees standard deviation during the last training session). Subjects clearly learned to compensate, at least partially, for the delayed vestibular feedback. Performance during the Post-test showed a negative aftereffect: The performance with a 500 ms delay worse during the Post-test than during Baseline (2.48 degrees versus 1.37 degreees), suggesting that the improvement seen during training was the result of intersensory temporal adaptation.
