Braun J, Haynes J D, Heinze H J, 2002, "Imaging contextual modulation in area V1" Perception 31 ECVP Abstract Supplement
Imaging contextual modulation in area V1
J Braun, J D Haynes, H J Heinze
We used event-based fMRI to study the contribution of area V1 to contextual salience. Six subjects viewed Gabor elements arranged in two ellipses (main axis diameter 4 deg) to the left and to the right of fixation. Observers were cued to report ellipse shape (main axis orientation) on either the left, the right, or both sides of fixation. The orientation of Gabor elements assumed one of three configurations: tangential, normal, or random to the ellipse, creating a closed contour, a radial pattern, or a random pattern, respectively. Both the reported side(s) and the Gabor configuration were randomly interleaved and trials were well separated in time (16 s). Gabor con- figuration altered the BOLD response significantly in area V1, and possibly other retinotopic areas, but apparently not in non-retinotopic areas such as area LO. This would appear to contrast with previous studies of visual segmentation, which produced little evidence for functional specialisation among visual cortical areas (eg Mendola et al, 1999 Journal of Neuroscience 19 8560 - 8572). Our results are consistent with the notion that area V1 and its intrinsic connectiviy make a specific and unique contribution to contextual salience. In addition, results obtained with various alternative stimulus configurations tell a cautionary tale about the interpretation of MRI data.
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