Non-Retinotopic Reference Frames in Human Vision: A Dynamic Journey from Visual Chaos to Clarity
Noory Meshkate, Babak
MetadataShow full item record
The optics of the eye maps neighboring points in the environment to neighboring retinal photoreceptors, and these neighborhood relations, known as retinotopic organization, are qualitatively preserved in early visual cortical areas. Under normal viewing conditions, due to object and observer movements in the environment, the stimuli impinging on retinotopic representations are highly dynamic and unstable. Thus, understanding ecological vision requires an understanding of how visual processes operate under these dynamic conditions. Retinotopically based theories, however, are not sufficient to explain how clarity of form is achieved in a dynamic environment. Non-retinotopic theories provide an alternative to address dynamic issues associated with purely retinotopic theories. Indeed, recent studies have indicated that many visual attributes of a stimulus are computed according to non-retinotopic reference frames. While those studies show the involvement of non-retinotopic reference frames in visual computation, the nature and spatio-temporal characteristics of these reference frames remain largely unknown. The primary goal of our research was to understand the nature and spatio-temporal properties of reference frames involved in non-retinotopic computations. Our results indicate that the effect of a dynamic non-retinotopic reference frame extends over space, creating a field within which target stimuli are localized and perceived relative to the reference. The fields of neighboring dynamic reference frames interact; static neighbors do not affect the fields of dynamic references; the non-retinotopic field effect is maximized when the target and the reference stimuli are in phase; and the field strength decreases with target-reference phase shift. The results of our visual masking experiments indicate that while masking mechanisms operate in retinotopic domain, masking effect attenuates significantly in the presence of predictable non-retinotopic reference frames. We suggest that the reference frame revealed by our studies can be better described in terms of a “field” rather than an object. Our results also indicate that the interactions between reference frames occur only when they are in motion; suggesting that the fields generated by non-retinotopic reference frames are motion-based. In conclusion, this work reveals that the dynamic nature of our visual experience should be viewed as part of the solution, rather than a problem in ecological vision.