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JL Hay, G Hesselmann, M Milders, M Niedeggen, A Sahraie; Effect of Attention on Motion Integration Capabilities: A Psychophysical Approach . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3871.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:Transient deficits in visual motion perception can be obtained in normal observers if temporal selective attention is required in a rapid serial visual presentation (RSVP). This deficit seems to mimic the sustained motion blindness following lesions in area MT. We have aimed to address whether (a) attention affects motion coherence thresholds and (b) the recovery from transient motion blindness depends on the level of motion integration. Methods: Subjects viewed two synchronised RSVP streams, a local stream defined by a fixation point changing colour every 100 ms, and a global stream consisting of random dots, displaced randomly or coherently. The primary task was to detect the onset of a red fixation colour (T1), which cued the subjects to direct attention to the global stream and to detect the onset of a 100 ms coherent motion episode (T2). In order to determine motion coherence thresholds (Exp.1, n=10), T1 and T2 occurred simultaneously (SOA 0ms), and the coherence of the motion target was varied from 4 to 100%. Differences in the recovery from motion blindness - obtained from SOA 0 to 500ms - were measured for three levels of coherence (30, 45, and 60%, Exp.2, n=15). Results: If the target motion T2 was a unique coherent motion in the global stream, the mean motion coherence threshold was approximately 12%. If T1 and T2 were preceded by irrelevant coherent motion distractors, the detectability of T2 was significantly reduced and the motion coherence thresholds increased to 28%. Similarly, detection of the coherent target motion in the second experiment was more attenuated for smaller (30%) than for larger (60%) coherent motion signal strengths. However, the slope of the attentional recovery function (measured as a function of SOA) did not differ between the levels of target coherence. Conclusion: Comparable to the effect of extrastriate brain lesions, attentional demands can increase the threshold for perceiving motion coherence. The attentional effect on motion integration can be described in terms of a top-down regulation which parallels recent neurophysiological findings.
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