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Xin Huang, Thomas D. Albright, Gene R. Stoner; Adaptive motion integration and antagonism in visual area MT. Journal of Vision 2005;5(8):81. doi: 10.1167/5.8.81.
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© ARVO (1962-2015); The Authors (2016-present)
Neuronal responses to stimuli within the classical receptive field (CRF) of area MT can be modulated by stimuli in the CRF surround. This modulation is usually characterized as antagonistic. However, we have found that, under some circumstances, motion in the surround is integrated with that in the CRF (Huang et al. 2004, SFN Abs. 935.13). In that experiment, one contour of a moving square (20° across) was centered in the CRF, with the rest of the square in the surround. Squares translated diagonally in one of four directions. Due to the aperture problem, the motion of the contour within the CRF was in one of only two directions. Directional tuning was established by responses to moving gratings within the CRF. We found that MT responses to a given motion in the CRF were stronger when the square (and hence features in the surround) moved in a preferred relative to a less preferred direction. MT responses thus reflected the global motion of the square and this required CRF-surround integration rather than antagonism.
To determine the role of stimulus configuration in surround modulation, we replaced the contour passing through the CRF with a circular patch of dots having the same velocity as the local motion of the contour. We compared the surround modulation observed for these stimuli with that elicited by intact squares. The unambiguously moving features in the surround were identical for the two stimulus types. As before, we found that CRF-surround interactions for intact squares were integrative. However, with moving dots in the CRF, surround modulation became antagonistic: neuronal responses were weaker when surround features moved in a preferred relative to a less preferred direction. Integrative and antagonistic modulations were both delayed relative to RF responses. These results demonstrate that surround modulation in area MT is adaptive and can switch from antagonistic to integrative depending upon visual context.
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