The Perceived Position of Moving Objects: Transcranial Magnetic Stimulation of Area MT+ Reduces the Flash-Lag Effect

Department of Psychology, University of California Berkeley, Berkeley, CA 94720, USA.
Cerebral Cortex (Impact Factor: 8.67). 02/2012; 23(1). DOI: 10.1093/cercor/bhs021
Source: PubMed


How does the visual system assign the perceived position of a moving object? This question is surprisingly complex, since
sluggish responses of photoreceptors and transmission delays along the visual pathway mean that visual cortex does not have
immediate information about a moving object's position. In the flash-lag effect (FLE), a moving object is perceived ahead
of an aligned flash. Psychophysical work on this illusion has inspired models for visual localization of moving objects. However,
little is known about the underlying neural mechanisms. Here, we investigated the role of neural activity in areas MT+ and
V1/V2 in localizing moving objects. Using short trains of repetitive Transcranial Magnetic Stimulation (TMS) or single pulses
at different time points, we measured the influence of TMS on the perceived location of a moving object. We found that TMS
delivered to MT+ significantly reduced the FLE; single pulse timings revealed a broad temporal tuning with maximum effect
for TMS pulses, 200 ms after the flash. Stimulation of V1/V2 did not significantly influence perceived position. Our results
demonstrate that area MT+ contributes to the perceptual localization of moving objects and is involved in the integration
of position information over a long time window.

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Available from: Gerrit W Maus
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    • "The FLE (Maus et al., 2013) and RM (Senior et al., 2002) are disrupted by transcranial magnetic stimulation of area MT. Kimura et al. (2011) suggested visual mismatch negativity might be related to the FLE and to RM. RM activates prefrontal cortex and anterior cingulate cortex (Rao et al., 2004); surprisingly, imaging information on the FLE has not been reported (although see Nijhawan, 2008, for discussion of potentially relevant neural mechanisms). "
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    ABSTRACT: In the flash-lag effect (FLE) and in representational momentum (RM), the represented position of a moving target is displaced in the direction of motion. Effects of numerous variables on the FLE and on RM are briefly considered. In many cases, variables appear to have the same effect on the FLE and on RM, and this is consistent with a hypothesis that displacements in the FLE and in RM result from overlapping or similar mechanisms. In other cases, variables initially appear to have different effects on the FLE and on RM, but accounts reconciling those apparent differences with a hypothesis of overlapping or similar mechanisms are suggested. Given that RM is simpler and accounts for a wider range of findings (i.e., RM involves a single stimulus rather than the relationship between two stimuli, RM accounts for displacement in absolute position of a single stimulus and for differences in relative position of two stimuli), it is suggested that (at least some cases of) the FLE might be a special case of RM in which the position of the target is assessed relative to the position of another stimulus (i.e., the flashed object) rather than relative to the actual position of the target.
    Full-text · Article · May 2013 · Frontiers in Psychology
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    • "At these fine scales, a number of visual phenomena show remarkable dissociations between the perceived position of an object and its retinal or spatial position; for example, motion in the visual field can shift the perceived positions of stationary or moving objects (Frö hlich, 1923; Ramachandran and Anstis, 1990; De Valois and De Valois, 1991; Nijhawan, 1994; Whitney and Cavanagh, 2000; Krekelberg and Lappe, 2001; Whitney, 2002; Eagleman and Sejnowski, 2007). Disrupting activity in area MT+ by transcranial magnetic stimulation (TMS) reduces these motion-induced mislocalization illusions (McGraw et al., 2004; Whitney et al., 2007; Maus et al., 2013). This is strong evidence for an involvement of MT+ in these illusions, yet it does not resolve questions about the underlying spatial representation in area MT+. "
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    ABSTRACT: How is visual space represented in cortical area MT+? At a relatively coarse scale, the organization of MT+ is debated; retinotopic, spatiotopic, or mixed representations have all been proposed. However, none of these representations entirely explain the perceptual localization of objects at a fine spatial scale-a scale relevant for tasks like navigating or manipulating objects. For example, perceived positions of objects are strongly modulated by visual motion; stationary flashes appear shifted in the direction of nearby motion. Does spatial coding in MT+ reflect these shifts in perceived position? We performed an fMRI experiment employing this "flash-drag" effect and found that flashes presented near motion produced patterns of activity similar to physically shifted flashes in the absence of motion. This reveals a motion-dependent change in the neural representation of object position in human MT+, a process that could help compensate for perceptual and motor delays in localizing objects in dynamic scenes.
    Full-text · Article · May 2013 · Neuron
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    ABSTRACT: We employed audiovisual stream/bounce displays, in which two moving objects with crossing trajectories are more likely to be perceived as bouncing off, rather than streaming through, each other when a brief sound is presented at the coincidence of the two objects. However, Kawachi and Gyoba (Perception 35:1289-1294, 2006b) reported that the presence of an additional moving object near the two objects altered the perception of a bouncing event to that of a streaming event. In this study, we extended this finding and examined whether alteration of the event perception could be induced by the visual context, such as by occluded object motion near the stream/bounce display. The results demonstrated that even when the sound was presented, the continuous occluded motion strongly biased observers' percepts toward the streaming percept during a short occlusion interval (approximately 100 ms). In contrast, when the continuous occluded motion was disrupted by introducing a spatiotemporal gap in the motion trajectory or by removing occlusion cues such as deletion/accretion, the bias toward the streaming percept declined. Thus, we suggest that a representation of object motion generated under a limited occlusion interval interferes with audiovisual event perception.
    Full-text · Article · Jan 2013 · Attention Perception & Psychophysics
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