Working Memory Load Effects on the Tilt Aftereffect.

Prolonged exposure to an oriented stimulus causes a subsequent test stimulus to be perceived as tilted in the opposite direction, a phenomenon referred to as the tilt aftereffect (TAE). Previous studies have demonstrated that high-level cognitive functions such as attention can modulate the TAE, which is generally well-known as a low-level perceptual process. However, it is unclear whether working memory load, another high-level cognitive function, could modulate the TAE. To address this issue, here we developed a new paradigm by combining a working memory load task with a TAE task. Participants firstly remembered a stream of digits (Experiment 1) or four color-shape conjunctions (Experiment 2) under high/low load conditions, and then recognized the probe stimuli (digits or a color-shape conjunction), which were presented at the center of an adapting grating. After the recognition task (i.e., the adaptation stage), participants performed an orientation judgment task to measure their TAEs. The result of Experiment 1, where the load stimuli were digits, showed that the magnitude of the TAEs were reduced under the condition of the high working memory load compared to that of the low working memory load. However, we failed to replicate the finding in Experiment 2, where the load stimuli were color-shape conjunctions. Together, our two experiments provided mixed evidence regarding the working memory load effects on the TAE and further replications are needed in future work.

Lower recognition thresholds for sad facial expressions in subthreshold depression: a longitudinal study.

Subthreshold depression (StD) is more prevalent than major depressive disorder (MDD) all over the world. Previous studies have indicated that depression is associated with impaired perception of facial expressions. However, for individuals with StD, whether perceptual sensitivity toward facial expressions could be altered and whether these alterations could stabilize over time remain largely unknown. Using the QUEST psychometric procedure, here we assessed recognition thresholds of five facial expressions (angry, fear, happy, sad and neutral) for individuals with StD and non-depressed controls. These subjects were retested after approximately 2-month time intervals. At the initial assessment, individuals with StD demonstrated lower recognition thresholds (i.e., stronger sensitivity) for only sadness compared to non-depressed controls. At the follow-up assessment, we classified the StD group as two subgroups: the non-remitted and the remitted group. For the former, lower recognition thresholds for only sadness were again found; for the latter, there was no significant difference. More importantly, individuals displaying lower recognition thresholds for sadness at the initial assessment were less likely to improve in depressive symptoms at the follow-up assessment. These results indicate that the alteration of perceptual sensitivity toward the sad expression for individuals with StD is associated with the current clinical state.