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Vanda Nemes, David Whitaker, James Heron, Declan McKeefry; Multiple Spatial Frequency Channels in Human Visual Perceptual Memory. Journal of Vision 2011;11(11):1278. doi: 10.1167/11.11.1278.
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Current models of short-term visual perceptual memory invoke mechanisms that are closely allied to low-level perceptual discrimination processes. The purpose of this study was to investigate the extent to which human visual perceptual memory for spatial frequency is based upon multiple, spatially tuned channels similar to those found in the earliest stages of visual processing. We measured how performance in a delayed spatial frequency discrimination paradigm was affected by the introduction of interfering or ‘memory masking’ stimuli of variable spatial frequencies during the delay period. Masking stimuli induced shifts in the point of subjective equality (PSE) when their spatial frequency was within a bandwidth of 1.2 octaves of the reference spatial frequency. When mask spatial frequencies differed by more than this value, there was no change in the PSEs from baseline levels. This selective pattern of masking was observed for different spatial frequencies and demonstrates the existence of multiple, spatially tuned mechanisms in visual perceptual memory. Masking effects were also found to occur for horizontal separations of up to 6° of visual angle between the masking and test stimuli. These findings add further support to the view that low-level sensory processing mechanisms form the basis for the retention of spatial frequency information in perceptual memory. However, the broad range of transfer of memory masking effects across spatial location indicates more long range, long duration interactions between spatial frequency channels that are likely to rely on contributions from neural processes located in higher visual areas.
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