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Scott N. Watamaniuk, Anca Velisar, Jeremy B. Badler, Stephen J. Heinen; Effects of motion adaptation on smooth pursuit performance. Journal of Vision 2004;4(8):116. doi: 10.1167/4.8.116.
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Prolonged viewing of a motion stimulus can produce adaptation, leading to the perception that subsequent stimuli with similar motion characteristics are moving slower (Bex et al., 1999). We previously reported that pursuit eye velocity was lower when the motion of the target spot was in the same direction as the adapting stimulus than when it was in the opposite direction (Heinen et al., 2003). This effect occurred for pursuit directions that differed from the adapting direction by up to 130 deg, consistent with estimates of the spacing of non-overlapping motion detectors (Ball & Sekuler, 1983). Since adaptation to motion also produces a motion aftereffect (MAE), one might expect pursuit velocity opposite the adapting direction to be increased. This did not occur. However, the strong motion signal of the pursuit stimulus may have masked the contribution of a relatively weak MAE to the pursuit response. Here, we report experiments done to determine if this was true, and to assess the sensitivity of pursuit adaptation in general to different target speeds. Smooth pursuit was measured for human observers tracking a 0.1 deg white spot moving across a computer monitor following 60 sec of adaptation to a random-dot cinematogram (10 deg diam. circular aperture, 128 dots) in which all dots moved at 10 deg/sec in one direction. Observers pursued targets that moved at speeds of 0–16 deg/sec in the same or opposite direction. After each trial, adaptation was topped-up with a 5 sec interval of the adapting stimulus. In general, following adaptation pursuit eye velocity showed a high-pass function with respect to target speed, such that eye velocity was reduced for targets moving in the adapted direction at speeds at or greater than the adapting speed. Eye velocity for slower targets was unaffected. Furthermore, no change in eye velocity was observed opposite the direction of adaptation, even at lower speeds. Under the present conditions, we found no evidence of the MAE influencing smooth pursuit.
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