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F. A. J. Verstraten, R. J. A. Wezel; Nulling the motion aftereffect of transparent motion. Journal of Vision 2001;1(3):162. doi: 10.1167/1.3.162.
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Purpose: While adapting to transparent motion (in our case in orthogonal directions), observers clearly perceive two superimposed patterns moving in different directions. However, in case both speeds are equal the direction of the motion aftereffect is unidirectional: the inverse of the vector sum of both patterns (e.g. Verstraten et al, Vis. Res. 1994). The neural substrates that are assumed to underlie transparent motion show surprising characteristics (Treue et al, Nature Neuroscience, 2000). We are interested in how the MAE of transparent motion can be nulled, by presenting unidirectional motion opposite to the undirectional MAE or by presenting a transparent nulling pattern in the direction of both adapting patterns. Methods: After adaptation to orthogonal patterns (about 2 deg/s), we presented a unidirectional or a transparent nulling pattern and we looked for the point of subjective standstill. Results: The MAE can be nulled by unidirectional motion but not by transparent motion. In the latter case, the nulling patterns remain visible and seem to move in different than their physical directions. A control experiment, where the nulling patterns where shown without prior adaptation, showed that the effect was larger than would be expected on motion repulsion effects. Conclusion: Nulling the aftereffect of transparent motion is possible with unidirectional motion but not for orthogonal transparent motion nulling patterns. In the latter case the aftereffect seems to add to the physical motions resulting in a different perceived direction.
VerstratenF.A.J.FredericksenR.E.GrindW.A.van de(1994). The aftereffect of bi-vectorial tranparent motion. Vision Research, 34, 349–358
TreueS.HolK.RauberH.J.(2000). Seeing multiple directions of motion-physiology and psychophysics. Nature Neuroscience, 3, 270–276.
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