1/5/2024 0 Comments Visual capture![]() ![]() ![]() Moreover, stimulation/foveation of a given part significantly raised the likelihood of ‘fragmented visual capture’ of that part in the mirror (e.g., simultaneously perceiving the hand but NOT the forearm in the ‘mirror’ location, when the hands were stroked). Analyses of participants’ perceived positions of their hand and forearm revealed stronger ‘local’ effects of visual capture at the site of stimulation (Experiment 1) or foveation (Experiment 2), as participants were significantly more likely to perceive either part of their hidden arm ‘in the mirror’ when it was the location of stimulation/foveation. In Experiment 2, we manipulated visual input variance by having participants fixate on either their hand or forearm while they were stroked synchronously across both parts. In Experiment 1, we manipulated the degree of cross-modal congruence between the two parts by synchronously stroking either the hands or the forearms, in isolation. Given the tendency to experience the body as a unitary whole composed of connected body parts, what happens when optimal integration of immediate multisensory information leads to ‘disconnected’ positions for connected body parts? We explored this question in two experiments, where participants’ hands were placed at unequal distances on either side of a mirror to create a spatial disparity between the ‘visual’ and ‘proprioceptive’ estimates of the hand and forearm behind the mirror. Previous studies have primarily explored how these factors influence visual capture of a single, stimulated body part (e.g., visual capture of a viewed ‘mirror hand’ during synchronous bimanual movements), with limited investigations into how adjacent, unstimulated body parts are represented. This effect is attributed to two main factors influencing multisensory integration: (1) cross-modal congruence between visual, tactile and/or motor signals, and (2) lower unisensory variance of vision compared to proprioception, weighting the integrated outcome toward the 'visual' input ('mirror hand'). We also observed that the kinesthetic percept depended strongly on identifying the viewed hand as your own, suggesting that visual capture is driven by the visual recognition (or “What”) pathway as well as by the visual spatial location (or “Where/How”) pathway.In the mirror box illusion, synchronous multisensory stimulation of a hidden hand alongside a reflected hand in the mirror can lead to 'visual capture' – where participants experience their hidden hand in the location of the reflected ‘mirror hand’. Consistent with Shimojo's work on visual capture, we observed that shifting the focus of attention influenced both the visual and capture percepts. Subjects reported feeling mildly disturbed but amused by impossible motion. When the hand was positioned so that “anatomically impossible” motion was perceived visually, the kinesthetic percept persisted. Four different canonical hand positions were employed which produced kinesthetic sensations referred to the wrist, elbow, or one of two knuckle joints. Subjects reported the sensation as a non-painful “tingling” which was largely localized to the joint or joints required to produce the motion observed visually. The sensation typically grew with repeated cycling and with additional trials. The kinesthetic sensation typically required several cycles in order to approach full strength. In addition, subjects reported a kinesthetic sensation that their own hand was being moved. At this speed and distance, visual apparent motion was induced within a few cycles. By winking or with the aid of stereo goggles, subjects alternated (1–2 Hz) between left and right eye views of their stationary hand. ![]() At this distance, the two eyes receive disparate views of the hand with different occlusions. Subjects held their hand 6–12 inches in front of their eyes. ![]() Here, we report a kinesthetic form of visual capture. In prior studies, it has been reported that viewing one's own hand through a displacing prism can shift the sense of hand position and cause large reaching errors. “Visual Capture” describes a class of phenomena in which visual perception strongly influences a somatosensory percept. ![]()
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