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Julien Dubois, Christof Koch, Rufin VanRullen; Visual trails: When perceptual continuity breaks down. Journal of Vision 2011;11(11):771. doi: 10.1167/11.11.771.
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© ARVO (1962-2015); The Authors (2016-present)
“Visual trailing” is a transient but dramatic disturbance of visual motion perception of unknown origin: the subject perceives a series of discrete stationary images trailing in the wake of otherwise normally moving objects. Although this phenomenon is most frequently encountered after ingestion of prescription and/or illicit drugs (i.e. Lysergic Acid Diethylamid or LSD), it has also occasionally been reported following brain damage or neurological disorders. Visual trails, because of their discrete and repetitive nature, may represent the perceptual manifestation of an underlying periodic neural process. This periodicity could arise outside of the visual system altogether (e.g. eye movements, motor tremor), or may be the result of faulty motion computation mechanisms (e.g. motion smear suppression), or finally, may point to a more general oscillatory process that affects, among other things, the motion perception system. However, only qualitative case reports exist in the literature, and a quantitative account of visual trails is currently lacking. We report our attempt to collect both qualitative and quantitative data on this phenomenon by means of an online survey. We simulated visual trails in a short movie and varied the interval between successive persisting images of moving objects (10 intervals between 25 and 250 ms); then we instructed past users of LSD (as assessed via a questionnaire) to report which sequence best corresponded to their experience of visual trails. Although the survey is still ongoing, we present results from more than 200 responses. Participants consistently selected a time interval between images of 60 ms on average, corresponding to an underlying periodicity in the 15–20 Hz (beta) range. This is but a preliminary step, and we suggest key experiments that should help identify the oscillatory underpinnings of this rare disturbance, and eventually lead to important insights into how our brains update conscious visual perception in time.
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