The perception of three-dimensional cast-shadow structure is dependent on visual awareness

Khuu, Sieu K.; Gordon, Jack; Balcomb, Kaleah; Kim, Juno

doi:10.1167/14.3.25

Cited by 12 publications

(9 citation statements)

References 51 publications

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“…Despite the strength of this phenomenon, the underlying neuronal mechanisms are unknown. A recent study has revealed that the motion in depth in the SOC illusion is perceptually comparable with that represented by binocular disparity [24]. Taken together with the observations previously described, this finding strongly suggests that the hMT+ is also involved in the perceptual process of the SOC illusion.…”

Section: Introductionsupporting

confidence: 75%

“…The direct inputs to the hMT+ from subcortical structures on the visual pathway, such as the lateral geniculate nucleus (LGN), superior colliculus (SC), and pulvinar (PL), have been considered the most likely alternative pathway, bypassing V1 and thereby accounting for the residual vision of blindsight patients [42, 43]. It has also been shown that the motion of the square in depth in the SOC illusion can be perceived even when the motion of the cast shadow is masked and processed unconsciously [24]. These observations suggest that there may be different visual pathways for processing monocular depth cues with and without consciousness, and that the hMT+ may be a key area for integrated motion perception in depth produced by those cues.…”

Section: Discussionmentioning

confidence: 99%

“…A moving cast shadow is a powerful monocular depth cue for the perception of motion toward and away from the observer [21–24]. This is effectively demonstrated by the ‘square-over-checkerboard’ (SOC) motion illusion.…”

Section: Introductionmentioning

confidence: 99%

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Activation of the Human MT Complex by Motion in Depth Induced by a Moving Cast Shadow

2016

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A moving cast shadow is a powerful monocular depth cue for motion perception in depth. For example, when a cast shadow moves away from or toward an object in a two-dimensional plane, the object appears to move toward or away from the observer in depth, respectively, whereas the size and position of the object are constant. Although the cortical mechanisms underlying motion perception in depth by cast shadow are unknown, the human MT complex (hMT+) is likely involved in the process, as it is sensitive to motion in depth represented by binocular depth cues. In the present study, we examined this possibility by using a functional magnetic resonance imaging (fMRI) technique. First, we identified the cortical regions sensitive to the motion of a square in depth represented via binocular disparity. Consistent with previous studies, we observed significant activation in the bilateral hMT+, and defined functional regions of interest (ROIs) there. We then investigated the activity of the ROIs during observation of the following stimuli: 1) a central square that appeared to move back and forth via a moving cast shadow (mCS); 2) a segmented and scrambled cast shadow presented beside the square (sCS); and 3) no cast shadow (nCS). Participants perceived motion of the square in depth in the mCS condition only. The activity of the hMT+ was significantly higher in the mCS compared with the sCS and nCS conditions. Moreover, the hMT+ was activated equally in both hemispheres in the mCS condition, despite presentation of the cast shadow in the bottom-right quadrant of the stimulus. Perception of the square moving in depth across visual hemifields may be reflected in the bilateral activation of the hMT+. We concluded that the hMT+ is involved in motion perception in depth induced by moving cast shadow and by binocular disparity.

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Section: Introductionsupporting

confidence: 75%

Section: Discussionmentioning

confidence: 99%

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Activation of the Human MT Complex by Motion in Depth Induced by a Moving Cast Shadow

2016

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“…This seems to be related to the evidence that the shadow of a person's body contributes to the connection between personal and extrapersonal space and triggers an automatic focus of attention toward the body part casting the shadow (Pavani & Galfano, 2015). Khuu, Gordon, Balcomb and Kim (2014) present results indicating that visual awareness is necessary for the perception of illusory motion from changes in cast shadows. The authors suggest that the perception of cast shadows is guided by two processes, one implicit that is responsible for the recognition of objects, and another demanding visual awareness to infer the object's 3D location.…”

Section: Introductionsupporting

confidence: 62%

Perception, cognition and reasoning about shadows

Santos

Casati

Cavanagh

2017

Spatial Cognition & Computation

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“…Note that such motion types are examples of motion informing the global form of the stimulus. This process might very well involve inputs from the ventral form pathway [47] , which might be reliant on conscious awareness for recognition [22] . Accordingly, such ‘motion forms and shapes’ might be susceptible to binocular suppression, indicating a dependency on visual awareness.…”

Section: Discussionmentioning

confidence: 99%

Unconscious Local Motion Alters Global Image Speed

et al. 2014

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Accurate motion perception of self and object speed is crucial for successful interaction in the world. The context in which we make such speed judgments has a profound effect on their accuracy. Misperceptions of motion speed caused by the context can have drastic consequences in real world situations, but they also reveal much about the underlying mechanisms of motion perception. Here we show that motion signals suppressed from awareness can warp simultaneous conscious speed perception. In Experiment 1, we measured global speed discrimination thresholds using an annulus of 8 local Gabor elements. We show that physically removing local elements from the array attenuated global speed discrimination. However, removing awareness of the local elements only had a small effect on speed discrimination. That is, unconscious local motion elements contributed to global conscious speed perception. In Experiment 2 we measured the global speed of the moving Gabor patterns, when half the elements moved at different speeds. We show that global speed averaging occurred regardless of whether local elements were removed from awareness, such that the speed of invisible elements continued to be averaged together with the visible elements to determine the global speed. These data suggest that contextual motion signals outside of awareness can both boost and affect our experience of motion speed, and suggest that such pooling of motion signals occurs before the conscious extraction of the surround motion speed.

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The perception of three-dimensional cast-shadow structure is dependent on visual awareness

Cited by 12 publications

References 51 publications

Activation of the Human MT Complex by Motion in Depth Induced by a Moving Cast Shadow

Activation of the Human MT Complex by Motion in Depth Induced by a Moving Cast Shadow

Perception, cognition and reasoning about shadows

Unconscious Local Motion Alters Global Image Speed

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