Biology subjects

DuBrow, S.

Publications and source records attributed to DuBrow, S..

5 recordsLinked to original sources

bioRxiv2024

Benefits of spaced learning are predicted by re-encoding of past experience in ventromedial prefrontal cortex

More than a century of research shows that spaced learning improves long-term memory. Yet, there remains debate concerning why. A major limitation to resolving theoretical debates is the lack of evidence for how neural representations change as a function of spacing. Here, leveraging a massive-scale 7T human fMRI dataset, we tracked neural representations and behavioral expressions of memory as participants viewed thousands of natural scene images that repeated at lags ranging from seconds to many months. We show that spaced learning increases the similarity of human ventromedial prefrontal cortex representations across stimulus encounters and, critically, these increases parallel and predict the behavioral benefits of spacing. Additionally, we show that these spacing benefits critically depend on remembering and, in turn, re-encoding past experience. Collectively, our findings provide fundamental insight into how spaced learning influences neural representations and why spacing is beneficial.

neuroscience↗

bioRxiv2022

Re-expression of CA1 and entorhinal activity patterns preserves temporal context memory at long timescales

Converging, cross-species evidence indicates that memory for time is supported by hippocampal area CA1 and entorhinal cortex. However, limited evidence characterizes how these regions preserve temporal memories over long timescales (e.g., months). At long timescales, memoranda may be encountered in multiple temporal contexts, potentially creating interference. Here, using 7T fMRI, we measured CA1 and entorhinal activity patterns as human participants viewed thousands of natural scene images distributed, and repeated, across many months. We show that memory for an images original temporal context was predicted by the degree to which CA1/entorhinal activity patterns from the first encounter with an image were re-expressed during re-encounters occurring minutes to months later. Critically, temporal memory signals were dissociable from predictors of recognition confidence, which were carried by distinct medial temporal lobe expressions. These findings suggest that CA1 and entorhinal cortex preserve temporal memories across long timescales by coding for and reinstating temporal context information.

neuroscience↗

bioRxiv2022

Agency as a Bridge to Form Associative Memories

The perception of agency occurs when individuals feel their decisions exert control over their environment. While agency can increase memory for items, most real-life situations are more complex. The decisions we make not only affect the item we act upon, but all the other items in direct proximity of our decisions. Here, we examined how an individuals agency to influence a situation affects their ability to learn associations between items that occur prior to and after making a decision. In our paradigm, participants were told they were playing a game show where they had to help a trial unique contestant choose between three doors. On agency trials, participants were allowed to pick any door they wanted. On forced-choice trials, participants were instructed to select a door that was highlighted. They then saw the outcome, a prize that was behind the selected door. Across two studies, participants show enhanced memory for contestants they saw in agency vs forced-choice trials. Memory benefits also extended to contestant - door and door - prize associations in both studies. Study 2 found this effect in the contestant - prize association. Notably, we found that agency also shaped the representation of memories such that they were stored as integrated sequences rather than individual relational pairs. Together, these data suggest agency over a situation leads to enhanced memory for all items in that situation. This enhanced binding for items may be occurring by the formation of causal links when an individual has agency over their learning environment.

neuroscience↗

bioRxiv2021

Mnemonic content and hippocampal patterns shape judgments of time

Our experience of time can feel dilated or compressed, rather than reflecting true "clock time." Although many contextual factors influence the subjective perception of time, it is unclear how memory accessibility plays a role in constructing our experience of and memory for time. Here, we used a combination of behavioral and fMRI measures to ask the question of how memory is incorporated into temporal duration judgments. Behaviorally, we found that event boundaries, which have been shown to disrupt ongoing memory integration processes, result in the temporal compression of duration judgments. Additionally, using a multivoxel pattern similarity analysis of fMRI data, we found that greater temporal pattern change in the left hippocampus within individual trials was associated with longer duration judgments. Together, these data suggest that mnemonic processes play a role in constructing representations of time. Statement of RelevanceOur everyday experiences convey a powerful truth: That our perception of time often diverges from the reality of time. When enjoying an active vacation with family, time moves quickly: hours go by in minutes. When sitting through an unnecessary meeting, time moves slowly: minutes go by in hours. What is the origin of these phenomenologically compelling illusions of time perception? Past research has examined how a range of specific factors, from emotions to blinking, contribute to the distortion of time. Here, in contrast, we evaluate how the content and accessibility of our memories shapes time perception. We show that context shifts, known to disrupt memory processing, also lead to robust contractions of perceived time. We discuss how both effects -- memory disruptions and time distortions -- may be linked via the hippocampus. "An hour, once it lodges in the queer element of the human spirit, may be stretched to fifty or a hundred times its clock length; on the other hand, an hour may be accurately represented on the timepiece of the mind by one second." -- Virginia Woolf

neuroscience↗

bioRxiv2018

Decision-making increases episodic memory via post-encoding consolidation.

The ability for individuals to actively make decisions engages regions within the mesolimbic system and enhances memory for chosen items. In other behavioral contexts, mesolimbic engagement has been shown to enhance episodic memory by supporting consolidation. However, research has yet to investigate how consolidation may support interactions between decision-making and episodic memory. Across two studies, participants encoded items that were occluded by cover screens and could either actively decide which of two items to uncover or were pre-selected by the experimenter. In Study 1, we show that active decision-making reduces forgetting rates across an immediate and 24-hour memory test, a behavioral marker of consolidation. In Study 2, we use functional neuroimaging to characterize putative neural markers of memory consolidation by measuring post-encoding interactions between the hippocampus and perirhinal cortex (PRC). We show that choice-related striatal engagement is associated with increased post-encoding hippocampal-PRC interactions. Finally, we show that a previous reported relationship between choice-related striatal engagement and long-term memory is accounted for by post-encoding hippocampal-PRC interactions. Together these findings support a model by which actively deciding to encode information enhances subsequent consolidation mechanisms to preserve episodic memory for outcomes.

neuroscience↗