PubMed · 7079102
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A Bowling, W Lovegrove. 1982. Iconic memory: fallacies persist (?).. https://doi.org/10.3758/bf03206222
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It has been previously reported that prolonged unidirectional smooth pursuit often produces a negative motion aftereffect (MAE). This was believed to be caused by retinal image motion of stationary environmental contours during pursuit which subsequently produced a primary motion aftereffect in the tracking direction. The peripheral MAE then induced motion in the stationary tracking target resulting in illusory movement in the opposite direction. We have found that a negative MAE is also produced when the adapting field is devoid of any contours. Furthermore, the presence of a moving textured background in conjunction with smooth pursuit produced an MAE whose direction was inconsistent with the induced motion hypothesis. Since all examples of motion aftereffects in this study were associated with the pursuit aspect of the experiment rather than any interactions with background contours, it was proposed that the illusory motion had an oculomotor determinant. A scheme was tentatively outlined in which fixation suppression of an unregistered ocular drift following prolonged pursuit adaptation (pursuit after-nystagmus) produced the post-adaptive motion illusions.
Both the tilt illusion and aftereffect exhibit indirect effects under certain conditions: these are negative (assimilation) effects which occur with large (70-90 deg) angular separations between test and inducing gratings. They are opposite in direction to the positive, and much larger, contrast effects which occur at smaller (10-15 deg) separations. Evidence from six experiments shows that stimulus manipulations which reduce direct effects have little or no effect on indirect effects and vice versa, suggesting that the two effects have different determinants. It is proposed that direct effects arise from lateral inhibitory interactions between populations of neurones in striate cortex and that indirect effects occur at a higher level, possibly in areas concerned with stimulus-specific interactions beyond the classic receptive field. The implications of the data for theories of the tilt illusion are considered.
A stationary vertical test grating appears to drift to the left after adaptation to an inducing grating drifting to the right, this being known as the motion aftereffect (MAE). Pattern-specific motion aftereffects (PSMAEs) induced by superimposed pairs of gratings in which the component gratings drift up and down but the observer sees a single coherent plaid drifting to the right have been investigated. Two experiments are reported in which it is demonstrated that the PSMAE is tuned more to the motion of the pattern than to the orientation and direction of motion of the component gratings. However, when subjects adapt to the component gratings in alternation, aftereffect magnitude is dependent upon the individual grating orientations and motion directions. These results can be interpreted in terms of extrastriate contributions to the PSMAE, possibly arising from the middle temporal area, where some cells, unlike those in striate cortex (V1), are tuned to pattern motion rather than to component motion.