Adaptive forgetting speed in working memory.

Working memory is known to be capacity-limited and is therefore selective not only for what it encodes but also what it forgets. Explicit forgetting cues can be used effectively to free up capacity, but it is not clear how working memory adaptively forgets in the absence of explicit cues. An important implicit cue that may tune forgetting in working memory is the passage of time. When information becomes irrelevant more quickly, working memory should also forget information more quickly. In three delayed-estimation experiments, we systematically manipulated how probing probability changed as time passed on after encoding an item (i.e., the "probing hazard"). In some blocks, probing hazard decreased after encoding an item, requiring participants to only briefly retain the memory item. In other blocks, the probing hazard increased or stayed flat, as the retention interval was lengthened. In line with our hypothesis, we found that participants adapted their forgetting rate to the probing dynamics of the working memory task. When the memory item quickly became irrelevant ("decreasing" probing hazard), forgetting rate was higher than in blocks where probing hazard increased or stayed flat. The time course of these adaptations in forgetting implies a fast and flexible mechanism. Interestingly, participants could not explicitly report the order of conditions, suggesting forgetting is implicitly sped up. These findings suggest that implicit adaptations to the temporal structure of our environment tune forgetting speed in working memory, possibly contributing to the flexible allocation of limited working memory resources.

Maintenance of color memoranda in activity-quiescent working memory states: Evidence from impulse perturbation.

In the present study, we used an impulse perturbation method to probe working memory maintenance of colors in neurally active and activity-quiescent states, focusing on a set of pre-registered analyses. We analyzed the electroencephalograph (EEG) data of 30 participants who completed a delayed match-to-sample working memory task, in which one of the two items that were presented was retro-cued as task relevant. The analyses revealed that both cued and uncued colors were decodable from impulse-evoked activity, the latter in contrast to previous reports of working memory for orientation gratings. Decoding of colors from oscillations in the alpha band showed that cued items could be decoded therein whereas uncued items could not. Overall, the outcomes suggest that subtle differences exist between the representation of colors, and that of stimuli with spatial properties, but the present results also demonstrate that regardless of their specific neural state, both are accessible through visual impulse perturbation.

Recovering object-location memories after sleep deprivation-induced amnesia.

It is well established that sleep deprivation after learning impairs hippocampal memory processes and can cause amnesia. It is unknown, however, whether sleep deprivation leads to the loss of information or merely the suboptimal storage of information that is difficult to retrieve. Here, we show that hippocampal object-location memories formed under sleep deprivation conditions can be successfully retrieved multiple days following training, using optogenetic dentate gyrus (DG) memory engram activation or treatment with the clinically approved phosphodiesterase 4 (PDE4) inhibitor roflumilast. Moreover, the combination of optogenetic DG memory engram activation and roflumilast treatment, 2 days following training and sleep deprivation, made the memory more persistently accessible for retrieval even several days later (i.e., without further optogenetic or pharmacological manipulation). Altogether, our studies in mice demonstrate that sleep deprivation does not necessarily cause memory loss but instead leads to the suboptimal storage of information that cannot be retrieved without drug treatment or optogenetic stimulation. Furthermore, our findings suggest that object-location memories, consolidated under sleep deprivation conditions and thought to be lost, can be made accessible again several days after the learning and sleep deprivation episode, using the clinically approved PDE4 inhibitor roflumilast.

Two faces of perceptual awareness during the attentional blink: Gradual and discrete.

In a series of experiments, the nature of perceptual awareness during the attentional blink was investigated. Previous work has considered the attentional blink as a discrete, all-or-none phenomenon, indicative of general access to conscious awareness. Using continuous report measures in combination with mixture modeling, the outcomes showed that perceptual awareness during the attentional blink can be a gradual phenomenon. Awareness was not exclusively discrete, but also exhibited a gradual characteristic whenever the spatial extent of attention induced by the first target spanned more than a single location. Under these circumstances, mental representations of blinked targets were impoverished, but did approach the actual identities of the targets. Conversely, when the focus of attention covered only a single location, there was no evidence for any partial knowledge of blinked targets. These two different faces of awareness during the attentional blink challenge current theories of both awareness and temporal attention, which cannot explain the existence of gradual awareness of targets during the attentional blink. To account for the current outcomes, an adaptive gating model is proposed that casts awareness on a continuum between gradual and discrete, rather than as being of either single kind. (PsycInfo Database Record (c) 2022 APA, all rights reserved).