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Luis D. Ramirez, Josh J. Foster, Sam Ling; Temporal attention selectively enhances gain only for target features. Journal of Vision 2020;20(11):322. doi: https://doi.org/10.1167/jov.20.11.322.
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Temporal attention – the allocation of attention to a moment in time – improves perception of visual targets at that moment. What mechanisms underlie temporal attention’s effects on perception? Perceptual template models (Lu and Dosher, 1998) highlight several mechanisms by which attention can improve perception. According to these models, attention can improve target perception through signal enhancement (i.e., increasing gain in sensory channels that encode the target stimulus, improving target discrimination even when the target is embedded in noise); stimulus enhancement (increasing gain across all sensory channels, which improves target discrimination solely when noise is low since noise would also be amplified); or noise reduction (reducing gain in channels that encode noise, which improves target discrimination solely when noise is high). To test which mechanism supports temporal attention, we measured contrast thresholds for a target grating embedded in varying levels of broadband noise in an orientation discrimination task. In half of the trials, temporal attention was directed by having the target onset preceded by an auditory pre-cue that allowed subjects to anticipate when the target would appear (cued condition). In the remaining trials, no auditory pre-cue was presented (uncued condition). We tested the mechanism supporting temporal attention by fitting a family of models that included signal enhancement, stimulus enhancement, noise exclusion, and all combinations of these mechanisms. Our modelling approach deviated from traditional perceptual template models in one important way: we incorporated divisive normalization to account for the cross-channel suppression that is known to occur between sensory channels (Baker and Vilidaite, 2014). We found that a temporal cue improved target discrimination across all noise levels, an empirical pattern that was best explained by a signal enhancement model. Thus, temporal attention appears to improve target perception by selectively increasing gain in sensory channels that are tuned solely for the target feature.
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