Visual Transients Reveal the Veridical Position of a Moving Object

Abstract

Article (Published Version) http://sro.sussex.ac.uk Kanai, Ryota and Verstraten, Frans A J (2006) Visual transients reveal the veridical position of a moving object. Perception, 35 (4). pp. [453][454][455][456][457][458][459][460] This version is available from Sussex Research Online: http://sro.sussex.ac.uk/43994/ This document is made available in accordance with publisher policies and may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the URL above for details on accessing the published version. Copyright and reuse:Sussex Research Online is a digital repository of the research output of the University.Copyright and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable, the material made available in SRO has been checked for eligibility before being made available.Copies of full text items generally can be reproduced, displayed or performed and given to third parties in any format or medium for personal research or study, educational, or not-for-profit purposes without prior permission or charge, provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. For example, when a flash physically coincides with a continuously moving object, the position of the moving object is perceived to be ahead of the flash. This visual phenomenon is called the flash-lag effectöFLE (Hazelhoff and Wiersma 1924; Metzger 1932, in Mateeff andHohnsbein 1988;MacKay 1961;Nijhawan 1994).At the input level of vision (eg the retina), a moving object and a flash should be aligned as they physically are. (1) Even after the retina, the positional representations in the very early stages should remain veridical. Only after certain stages of visual processing does the neural representation correspond to the perceived and sometimes illusory position, as opposed to physical position. In this hierarchical view of visual processing, there is a transition from a veridical representation to a more perceptual representation as the processing proceeds to a higher stage. Usually, stationary objects are perceived roughly at the veridical location. Therefore, we cannot experimentally dissociate the neural responses from the physical input and the neural representations corresponding to the perceived location. In mislocalisation illusions, however, the perceived position can be dissociated from the physical position on the retina. Thus, mislocalisation illusions such as the FLE offer an opportunity for isolating the neural substrates representing our sense of space in the visual brain.In the present study, we report a new visual phenomenon that illuminates the issue of physical versus perceived (or illusory) position. In the classical FLE stimulus, as shown Abstract. The position of a moving object is often ...

Knowledge-based Correction of Flash-lag Illusion

“…A recent study using face stimuli (Khurana, Carter, Watanabe, & Nijhawan, 2006) obtained results consistent with ours, although their findings could be explained by possibilities other than knowledge, such as a priming effect and a similarity of visual features between the two halves of their nonchimera faces. Taken together with several studies indicating an involvement of high-level neural mechanisms in the FLE (Kanai & Verstraten, 2006;Nieman, Nijhawan, Khurana, & Shimojo, 2006), our study strengthens the view that at least some portions of the flash-lag illusion cannot be attributed to low-level processing in the visual system.…”

Absence of flash-lag when judging global shape from local positions

“…The flash-lag illusion is a robust effect and, to our knowledge, only one study has found a lack of mislocalization between flashes and moving objects (Kanai & Verstraten, 2006). Kanai and Verstraten found that when a ring was flashed surrounding a moving disk, the percept corresponding to the disk split in two: one disc was perceived ahead of the flashed ring which reproduced the flash-lag effect, but the other appeared just centered inside the flashed ring showing no relative spatial mislocalization.…”

Crowding is tuned for perceived (not physical) location

“…While the relatively slow buildup of these positional displacements might argue for some role of feedback (Chung et al, 2007), the physiological data described above do not provide any direct evidence for effects arising within primary visual cortex (McGraw et al, 2004; Whitney et al, 2003). Additionally, behavioral evidence suggests that visual transients can restore the veridical position of moving elements (Kanai & Verstraten, 2006). This suggests that the De Valois effect is a later-stage process in vision, with the veridical signals maintained within the initial processing stages.…”

“…Investigations of the De Valois effect using functional MRI have shown that its magnitude does not correlate with activity in V1 (Whitney et al, 2003) and that it is disrupted only by transcranial magnetic stimulation (TMS) over area MT/V5, with no discernable effects from TMS over V1 (McGraw, Walsh, & Barrett, 2004). Further, visual transients can restore the veridical position of moving elements, suggesting that these veridical signals are maintained within V1 throughout (Kanai & Verstraten, 2006). Positional shifts can nonetheless be induced by crowded motion signals (Whitney, 2005), suggesting that these effects are produced by mid-level mechanisms.…”