Purchase this article with an account.
David Whitney, Herbert C Goltz, Christopher G Thomas, Melvyn A Goodale; Flexible retinotopy: Motion dependent position coding in visual cortex. Journal of Vision 2003;3(9):111. doi: 10.1167/3.9.111.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
A fundamental characteristic of the visual cortex is that it is organized retinotopically—relative positions on the retina are maintained in the cortex. Although this largely determines our perception of a stable world, there are a number of additional sources of information that contribute to the perceived positions of objects. For example, motion signals that are present in a scene can shift the apparent location of an object. Yet, it is not clear how or where in the brain motion and position signals are integrated. Here we show that the retinotopic representation of an object in visual cortex, as revealed by fMRI, is systematically shifted when there are motion signals present in the scene; strict retinotopy breaks down in the presence of motion. We presented stationary patches filled with moving texture and measured localized activation in visual cortex. Perceptually, the patches appear shifted in the direction of the moving texture. Surprisingly, the representation of the patches in visual cortex is also shifted by a comparable magnitude—but in a direction opposite that of perception (eye movements cannot explain the pattern of results). Peak activation for the patches occurs not where the patches appear, but in positions that correspond to where the patches are not perceived. That is, when a patch filled with moving texture appears shifted in position, there is a region of the visual field (the trailing edge of the moving texture) in which the stimulus is physically present but does not appear to be present. It is this region that produces peak activation. The results show that motion signals are incorporated into the retinotopic representation of an object's position even at early cortical visual areas. Moreover, the activation we observed correlated with what subjects did not perceive.
This PDF is available to Subscribers Only