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Pestilli Franco, Cigdem P. Talgar, Marisa Carrasco; Sustained attention enhances letter identification without affecting channel tuning. Journal of Vision 2004;4(8):524. doi: https://doi.org/10.1167/4.8.524.
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Background: Sustained attention has been found to improve contrast sensitivity in high (Lu & Dosher, 2000) and no noise (Ling & Carrasco, 2002) displays. Given that a single spatial frequency channel mediates letter identification (Solomon & Pelli, 1994), the critical-band-masking paradigm has been used to investigate whether transient attention affects the spatial frequency tuning of the channel. Although directing transient attention to the target location increased contrast sensitivity, it did not change the spatial frequency tuning of the channel mediating letter identification (Talgar, Pelli & Carrasco, 2004). Given that sustained attention is conceptually-driven and more flexible than transient attention, here we investigated whether when sustained attention is directed to the target location observers could switch channels to avoid noise and perform at a lower threshold (i.e., channel switching). Method: Observers performed a letter identification task. We manipulated attention using a sustained (a line at fixation indicating the target location) and a neutral (a dot at fixation) cue. Both cues indicated the time of target onset but only the sustained cue was informative regarding target location. The target letter (N, Z, or X; presented for 40 ms in low or high-pass noise with different cutoff frequencies) followed the cue at one of the 8 iso-eccentric locations. Distracter letters (V's) occupied the remaining 7 locations. We measured the energy threshold elevation at each of the low and high-pass cutoff noise frequencies. To derive frequency-dependent power gain of the inferred filter, we estimated the derivative of the threshold energy with respect to the cutoff frequency. Results: Directing sustained attention to the target location doubled observers' sensitivity (comparable to the effect of transient attention). Notwithstanding the presumed flexibility of sustained attention, it did not change the channel's bandwidth or its spatial frequency tuning.
NSF grant# BCS-9910734/HCP
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