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B.-R. Baltaretu, B. T. Dunkley, J. D. Crawford; Trans-saccadic integration of spatial frequency information in an fMRIa paradigm.. Journal of Vision 2014;14(10):1222. doi: 10.1167/14.10.1222.
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To date, there is no direct evidence showing where and how visual features are stored and integrated across saccades in the human brain. Recently, using an fMRI 'adaptation' paradigm we found two cortical regions that showed greater sensitivity to same vs. different stimulus orientations that were more robust with intervening saccades than fixation: one in the right inferior parietal lobule (supramarginal gyrus; SMG) and one in right extrastriate cortex, likely V4 (Dunkley and Crawford, Society for Neuroscience Abstracts 2012). Here, we used a similar paradigm to test if these trans-saccadic interactions are feature-specific. Eleven participants viewed a vertical grating of a given spatial frequency in the center of the screen whilst fixating to the left or right of the stimulus. Subsequently, a second stimulus was presented with the same spatial frequency (Repeated condition) or with a different spatial frequency (Novel condition). In the intervening period, participants were required to either fixate in the same position (Fixation task) or to make a saccade to the opposite fixation point (Saccade task). Participants were required to indicate if the stimulus changed or stayed the same. The Saccade task data produced significant (p <0.05) adaptation (novel > repeated frequency) in both left and right parietal cortex around SMG, consistent with our results from the previous spatial orientation study. However, we found no significant adaptation or summation effect around V4 (consistent with its known greater sensitivity to orientation vs. frequency). Results from the Fixation task showed significant adaptation in left inferior parietal cortex. Taken together with our previous experiment, this demonstrates that inferior parietal cortex is involved in trans-saccadic integration of both spatial orientation and frequency, whereas V4 is involved in field- and feature-specific integration for orientation. This suggests dual feature-specific and feature-independent mechanisms for trans-saccadic integration of objects in human cortex.
Meeting abstract presented at VSS 2014
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