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Yasuto Tanaka; Orientation-invariant perceptual memory. Journal of Vision 2007;7(9):856. doi: 10.1167/7.9.856.
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© ARVO (1962-2015); The Authors (2016-present)
In investigating temporal cueing effects on contrast discrimination (Tanaka and Sagi, 2006), we found orientation-invariant perceptual memory. A double priming technique was used in which a temporal cueing signals (peripheral crosses to cue timing of prime temporal onset) followed by the presentation of high contrast Gabor primes (C=0.16, above threshold, sigma=lambda=0.25 deg) Onset asynchrony between cue and prime was optimized at 450ms. Memory trace for the prime was tested by the target Gabor that followed the prime with the onset delay of 900ms (Tanaka and Sagi 1998). Cue, prime and target durations were all 100ms. Detection threshold of target was measured by a temporal 2IFC paradigm with the interval between 1st and 2nd displays randomized by 700±500ms. We found detection facilitation with the high-contrast primes by 0.25±0.01 log units when prime and target orientation was identical. Facilitation was found with diagonal (45 deg) as well as orthogonal (90deg shift) primes, by 0.26±0.01, and 0.20±0.01 log units, respectively (2 observers). These results point to orientation invariant memory traces for high-contrast signals. Furthermore, phase dependency was examined by testing prime phase shifting either 45, 90, 135, or 180 degrees. Facilitation was limited within 90 degrees (0.21±0.04 log units, averaged across 0, 45, 90 deg) with estimation of the half-width of half height=0.l9 degrees of visual angle, corresponding to a perceptual receptive field. Taking the size of the RF as well as orientation invariance into account, we suggest high-contrast perceptual memory generated before cortical levels of processing, possibly in LGN.
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