Alais D, Wenderoth P, Burke D
Department of Psychology, University of Sydney, Australia.
Vision Res. 1994 Jul;34(14):1823-34. doi: 10.1016/0042-6989(94)90307-7.
When motion aftereffects (MAEs) are measured by adapting to a drifting plaid (simultaneous adaptation) or by adapting to the plaid's component gratings in alternation (alternating adaptation), it has been shown that the velocity and duration of the MAE are smaller in the latter case [Wenderoth, P., Bray, R. & Johnstone, S. (1988) Perception, 17, 81-91; Burke, D. & Wenderoth, P. (1993) Vision Research, 33, 351-359]. However, Burke and Wenderoth additionally reported that the directions of MAEs induced by simultaneous and alternating adaptation were identical, an apparent inconsistency if the differences in duration and velocity were due to the presence of "blobs" at the component grating intersects in the simultaneous case. Presumably, the direction of the "blobs" should also affect perceived plaid direction during adaptation and, hence, the MAE direction. In five experiments, we have measured both perceived adapting plaid and MAE direction, tested with both alternating and simultaneous adaptation, measured interocular transfer of plaid-induced MAEs and obtained MAE and plaid direction judgments under monocular and binocular viewing conditions. All of the data indicate that there is a blob tracking mechanism which is preferentially stimulated by plaids whose component gratings have high spatial frequency, low temporal frequency and high contrast. Differences between simultaneous and alternating adaptation emerge only when more optimal blobs are used, thus accounting for Burke and Wenderoth's failure to find a difference. The data also support Burke and Wenderoth's claim that the blob tracking mechanism is monocular: alternating and simultaneous adaptation produce identical MAEs under interocular transfer conditions, even using plaids with more optimal blobs. We also report the unexpected finding that plaids with more- and less-optimal blobs appear to drift in directions 20 degrees apart yet their aftereffects differ in direction by only 3-5 degrees. That is, more optimal blob plaids--compared with less optimal blob plaids--change both perceived plaid direction during adaptation and subsequent perceived MAE direction but the latter change is much more modest. Possible explanations of this dissociation are considered.
当通过适应漂移的方格图案（同时适应）或通过交替适应方格图案的组成光栅（交替适应）来测量运动后效（MAE）时，研究表明，在后一种情况下MAE的速度和持续时间较小[温德罗斯，P.，布雷，R. & 约翰斯通，S.（1988年）《知觉》，第17卷，第81 - 91页；伯克，D. & 温德罗斯，P.（1993年）《视觉研究》，第33卷，第351 - 359页]。然而，伯克和温德罗斯还额外报告称，同时适应和交替适应所诱发的MAE方向是相同的，如果持续时间和速度的差异是由于在同时适应情况下组成光栅相交处存在“斑点”，这显然是不一致的。据推测，“斑点”的方向在适应过程中也应该会影响所感知的方格图案方向，进而影响MAE方向。在五个实验中，我们测量了所感知到的适应方格图案和MAE方向，分别用交替适应和同时适应进行测试，测量了方格图案诱发的MAE的双眼间转移，并在单眼和双眼观察条件下获得了MAE和方格图案方向的判断。所有数据表明，存在一种斑点跟踪机制，其优先受到组成光栅具有高空间频率、低时间频率和高对比度的方格图案的刺激。只有当使用更理想的斑点时，同时适应和交替适应之间的差异才会出现，这就解释了伯克和温德罗斯未能发现差异的原因。这些数据也支持了伯克和温德罗斯的观点，即斑点跟踪机制是单眼的：在双眼间转移条件下，交替适应和同时适应会产生相同的MAE，即使使用具有更理想斑点的方格图案。我们还报告了一个意外发现，具有更理想和不太理想斑点的方格图案似乎在相差20度的方向上漂移，但其后效在方向上仅相差3 - 5度。也就是说，与不太理想斑点的方格图案相比，更理想斑点的方格图案在适应过程中会改变所感知的方格图案方向以及随后所感知的MAE方向，但后者的变化要小得多。我们考虑了这种分离现象的可能解释。
