Abstract
Visual short-term memory (VSTM) load leads to impaired perception during maintenance. Here, we fitted the contrast response function to psychometric orientation discrimination data while also varying attention demand during maintenance to investigate: (1) whether VSTM load effects on perception are mediated by a modulation of the contrast threshold, consistent with contrast gain accounts, or by the function asymptote (1 lapse rate), consistent with response gain accounts; and (2) whether the VSTM load effects on the contrast response function depend on the availability of attentional resources. We manipulated VSTM load via the number of items in the memory set in a color and location VSTM task and assessed the contrast response function for an orientation discrimination task during maintenance. Attention demand was varied through spatial cuing of the orientation stimulus. Higher VSTM load increased the estimated contrast threshold of the contrast response function without affecting the estimated asymptote, but only when the discrimination task demanded attention. When attentional demand was reduced (in the cued conditions), the VSTM load effects on the contrast threshold were eliminated. The results suggest that VSTM load reduces perceptual sensitivity by increasing contrast thresholds, suggestive of a contrast gain modulation mechanism, as long as the perceptual discrimination task demands attention. These findings support recent claims that attentional resources are shared between perception and VSTM maintenance processes.
Highlights
Visual short-term memory (VSTM), termed visual working memory (e.g., Luck & Vogel, 1997), links perception with higher cognitive functions via maintenance of visual information for short periods of time (Fukuda, Awh, & Vogel, 2010; Johnson et al, 2013; Luck & Vogel, 2013)
In contrast to the consistent increase of contrast threshold with higher load observed when the stimulus location was uncertain, these findings demonstrate that the contrast gain effects of VSTM load were eliminated when spatial uncertainty was reduced, as is the case when attention demands on the orientation discrimination task are reduced by cuing the spatial location of the orientation stimulus
The present findings demonstrate that the effects of VSTM load on perception depend on the level of competition for attentional resources between VSTM maintenance and perception
Summary
Visual short-term memory (VSTM), termed visual working memory (e.g., Luck & Vogel, 1997), links perception with higher cognitive functions via maintenance of visual information for short periods of time (Fukuda, Awh, & Vogel, 2010; Johnson et al, 2013; Luck & Vogel, 2013). VSTM load was found to reduce the retinotopic response to a contrast increment presented during the maintenance delay in early visual cortex areas V1 to V3 (Konstantinou, Bahrami, Rees, & Lavie, 2012). These effects are in line with the sensory recruitment hypothesis (e.g., Serences, Ester, Vogel, & Awh, 2009; for more recent formulations, see Gayet, Paffen, & Van der Stigchel, 2018; Scimeca, Kiyonaga, & D’Esposito, 2018), which suggests that the brain network responsible for maintenance of visual information in memory involves the same sensory brain areas as those involved in perceptual encoding. The reduction of the V1 to V3 response to stimuli and accompanied findings of reduced detection sensitivity during the maintenance interval in conditions of higher VSTM load can be taken to reflect that loading VSTM depletes the sensory resources required for perceptual representations of incoming stimuli during maintenance
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