Neural correlates of the continuous Wagon Wheel Illusion: A functional MRI study

Abstract

After prolonged viewing of a continuous periodic motion stimulus at frequencies around 10 Hz, observers experience a fleeting impression of reversed motion: the continuous Wagon Wheel Illusion (c-WWI). To account for this phenomenon it has been proposed that attentional mechanisms discretely sample motion information. Alternative accounts argue that the illusion relies on the spurious activation of motion detectors, which under the effect of adaptation could trigger a reversed percept. We investigated the neural correlates of the c-WWI using fMRI (3T). Subjects viewed a vertically bisected ring containing a radial grating unambiguously rotating at 10 Hz; they continuously reported the perceived motion direction within each half of the ring. The two halves always rotated in opposite directions, allowing us to separately explore illusory reversals occurring within each hemifield. Comparing BOLD activity during illusory (c-WWI) or real perceptual periods revealed systematic differences in right parietal regions, in addition to the right motion complex MT+. This activation pattern did not depend on the side on which the illusion occurred, and could not be accounted for by purely perceptual switch-related activity-known to encompass parietal regions during other bistable effects. This first characterization of the fMRI correlates of the c-WWI may have implications for the different theoretical explanations of the phenomenon.

Pivotal role of hMT+ in long‐range disambiguation of interhemispheric bistable surface motion

“…Notably, we found a large and highly significant cluster in the superior parietal lobule (SPL) related to perceptual decisions, which seems to be part of the decision network involving hMT1, either in terms of switch-related or staterelated activity. The enhanced BOLD responses in SPL in response to perceptual decisions has been previously reported in fMRI studies [Knapen et al, 2011;Lumer et al, 1998;Lumer and Rees, 1999;Reddy et al, 2011;Weilnhammer et al, 2013]. Our results seem to agree with recent studies which revealed that switch-related fronto-parietal BOLD activity can be found in relation to perceptual switches irrespective of the role of other brain regions involved in behavioral choice [Brascamp et al, 2015;Intait _ e et al, 2016].…”

Different effects of aging and gender on the temporal resolution in attentional tracking

“…It is distinct from the temporal resolution of vision that underlies our perception of flicker (critical flicker fusion) or the temporal frequency limit of luminance-defined motion, among others (for review, see Holcombe, 2009). The neural basis of the temporal resolution of attention appears to lie in the posterior parietal cortex (Battelli, Pascual-Leone, & Cavanagh, 2007;Howard, Bashir, Chechlacz, & Humphreys, 2016;Reddy, Rémy, Vayssière, & VanRullen, 2011).…”

On the cyclic nature of perception in vision versus audition

“…Third, motion adaptation can be strictly dissociated from the c-WWI: by varying stimulus contrast or eccentricity, it is possible to increase the amount of motion adaptation (as measured by both the static and the dynamic motion aftereffects) while decreasing the c-WWI, and vice versa [27]. Lastly, there is converging evidence that the neural correlates of the c-WWI primarily involve the right parietal lobe [15,28,29]; if the illusion was due to adaptation of low-level motion detectors, then its correlates would probably not be expected in such a high-level hierarchical region.…”