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Brian Stone, Jessica Tinker; Capture of positive afterimages by the other senses: Extension of the body schema?. Journal of Vision 2013;13(9):1327. doi: 10.1167/13.9.1327.
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© ARVO (1962-2015); The Authors (2016-present)
Previous research utilizing the Rubber Hand Illusion has demonstrated that external objects can be incorporated into the body schema, but only under restricted conditions, such as when using realistic-looking prosthetic limbs in realistic postures. However, some have argued for a much more permissive view of body schema integration using a related multi-sensory interaction effect within an induced afterimage paradigm. In this paradigm, the participant sits in total darkness and then a bright flash briefly illuminates the scene, causing a vivid afterimage of whatever the participant was looking at. If the afterimage is of a body part, then subsequently moving that body part causes the afterimage of the moved part to fade, due to the conflict between proprioceptive feedback (of movement) and illusory visual feedback (a static afterimage). A recent study found that an object held in the hand and then moved or dropped caused the afterimage of the object – not just the body part holding it – to also fade. The authors argued that this represents a rapid assimilation of external objects into the body schema. The present study replicates and extends these results but tests an alternate account that does not rely on body schema extension. Rather, we argue that fading of the afterimage is due to non-visual sensory feedback updating the brain's representation of an external object's spatial position, and – as with the bodily afterimage effect – the multi-sensory conflict leads to over-writing of the illusory visual information, causing the afterimage to fade (i.e. non-visual capture). We found that auditory and somatosensory feedback of object movement were sufficient to evoke the afterimage fading effect, and our data do not fit parsimoniously with a 'body schema extension' account, but are consistent with a 'sensory feedback' account.
Meeting abstract presented at VSS 2013
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