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Harun Karimpur, Filipp Schmidt, Katja Fiehler; How spatial coding is affected by mid-level visual object properties within and outside of peripersonal space.. Journal of Vision 2019;19(10):218-219. https://doi.org/10.1167/19.10.218d.
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We show enhanced behavioral responses to objects in our immediate surround compared to objects outside of reach space. Backed up by many neurophysiological studies this finding established the concept of peripersonal space. Within peripersonal space, we spatially encode objects-for-action based on a combination of egocentric (object-to-self) and allocentric (object-to-object) information. However, it is not clear how the interaction between these reference frames is modulated by the affordance of an object and the distance to the observer. This is in line with the recently proposed action-field theory of peripersonal space. Rather to think of an in-or-out zone, the theory defines peripersonal space as a graded field reflecting the context-dependent relevance of our actions which either aim to avoid or approach objects. Here we tested the role of object-affordance in spatial coding for different distances by using a pointing task in virtual reality. We presented a target object surrounded by task-irrelevant landmarks within and outside the participant’s peripersonal space. After a brief mask and delay, the landmarks shortly reappeared without the target, either at the same position (baseline) or horizontally shifted. After their disappearance, participants were asked to point to the remembered target object within the empty scene. To manipulate the level of object-affordance, we varied mid-level visual object properties of shape and texture (spiky metallic versus soft rubber ball). We found that reaching endpoints deviated in the direction of landmark shifts suggesting the use of allocentric information. This effect was more strongly affected by mid-level visual object properties within compared to outside of peripersonal space. Our findings suggest that spatial coding in our immediate surround is modulated by object-affordance.
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