Human yaw rotation aftereffects with brief duration rotations are inconsistent with velocity storage.

In many sensory systems, perception of stimuli is influenced by previous stimulus exposure such that subsequent stimuli may be perceived as more neutral. This phenomenon is known as an aftereffect and has been studied for vision, audition, and some vestibular stimuli including roll and translation. Previous data on yaw rotation perception has focused on low-frequency stimuli on the order of a minute which may not be directly applicable to frequencies during ambulation. The aim of the current study is to look at the influence of yaw rotation on subsequent perception near 1 Hz, the predominant frequency of yaw rotation during human ambulation. Humans were rotated with 12 ° whole body adapting stimulus over 1 or 1.5 s. After an interstimulus interval (ISI) of 0.5, 1.0, 1.5, or 3 s, a test stimulus the same duration as the adapting stimulus was presented, and subjects pushed a button to identify the direction of the test stimulus as right or left. The direction and magnitude of the test stimulus was adjusted based on prior responses to find the stimulus at which no rotation was perceived. Experiments were conducted both in darkness and with a visual fixation point. The presence of a fixation point did not influence the aftereffect which was largest at 0.5 s with an average size of 0.78 ± 0.18°/s (mean ± SE). The aftereffect diminished with a time constant of ~1 s. Thresholds were elevated after the adapting stimulus and also decreased with a time constant of ~1 s. These findings demonstrate that short adapting stimuli can induce significant aftereffects in yaw rotation perception and that these aftereffects are independent from the previously described velocity storage.