Biology subjects

Schechtman, E.

Publications and source records attributed to Schechtman, E..

9 recordsLinked to original sources

bioRxiv2026

Reactivation during sleep segregates the neural representations of episodic memories

Sleep involves the reactivation of recently acquired memories, thereby shaping the neural representations supporting them. An essential feature of episodic memory (i.e., memory for events) is the link between specific elements (e.g., a cake) and the context in which they were embedded (e.g., a birthday party). We investigated how reactivation during sleep impacts item-context binding. Participants (N = 22) formed stories linking together objects in unique contexts. Using functional MRI, we measured the overlap between neural representations for contextually linked objects. During a 90-min nap, some object memories were reactivated by unobtrusively presenting object-specific sounds. Across multiple brain regions, reactivation reduced the overlap between representations of contextually linked memories, promoting object specificity. Furthermore, reactivation reduced the representational overlap between contexts, thereby promoting context specificity. Taken together, data suggest that reactivation during sleep decontextualizes memories. These results inform our understanding of how sleep contributes to interlinked memories embedded in naturalistic contexts and demonstrate that memory reactivation during sleep changes representations of memories within their distinctive contexts.

neuroscience↗

bioRxiv2026

EEG-based classification models reveal differential neural processing of words and images

BackgroundMachine learning methods employing neuroimaging data are useful for monitoring the activation of neural representations. Specifically, they can be used to discern the brain networks engaged in processing specific categories of items. This approach has been employed on neuroimaging data, including functional magnetic resonance imaging data and electroencephalography (EEG) data. New methodHere, we present a task and an analytical pipeline for investigating category representations using EEG. Participants (N = 30) viewed a series of images and words of objects belonging to five categories (Animals, Tools, Food, Scenes, and Vehicles) and responded when items from the same category were presented consecutively. ResultsWe trained support vector machines on EEG data within participants and found that both image trials and word trials yielded significant category classification accuracy, with image trials achieving higher accuracy than word trials. When comparing categories in a pair-wise fashion, all pairs were statistically distinguishable for image trials, whereas only one pair was distinguishable for word trials. Parietal and Left Temporal electrodes contributed more to image classification than Frontal and Right Temporal electrodes. Category-specific activity patterns also generalized across participants for image trials. Comparison with existing methodsOur data and analytic pipeline yielded high classification accuracies, primarily for image trials, providing support for the utility of EEG data for neural decoding. ConclusionsThese methods can be instrumental for exploring the activation and reactivation of neural representations at the category level during wakefulness and, potentially, during offline states.

neuroscience↗

bioRxiv2026

Depression symptoms are associated with affective neural processing during sleep and rest

Sleep supports offline information processing and is essential for cognitive and emotional functioning. Abnormal sleep patterns are a hallmark of affective disorders. We hypothesized that affective symptoms occur with maladaptive neural processing during offline periods. To test this idea, we used multivariate EEG decoding with cross-state classification. A model trained on EEG data acquired while participants (N = 52) viewed emotional images was used to classify stimulus valence. Applying this model to data collected during a nap revealed the re-emergence of affective neural patterns. Critically, offline reinstatement of patterns reflecting negatively valenced processing predicted greater depressive symptoms across participants. These associations reflected both cognitive-affective and somatic-performance depression subscales, and they generalized across sleep stages and wakeful rest. The finding that offline neural information processing is linked with emotional well-being supports a model whereby maladaptive negative biases can be perpetuated during rest, potentially shaping the progression of affective disorders.

neuroscience↗

bioRxiv2026

No evidence for sleep-dependent memory generalization in a large online sample

Memory generalization allows individuals to extract and apply information from prior experiences to novel situations, supporting flexible learning and efficient decision-making. Theoretical models suggest that sleep should facilitate generalization, yet the literature examining its role in promoting generalization is mixed. We recruited 137 participants via Prolific to complete an image-location memory task over two sessions spaced 12 hours apart. Participants were randomly assigned to the Wake group (learning in the morning) or the Sleep group (learning in the evening). In Session 1, participants learned the location of stimuli on the screen and were tested on their memory five minutes later. Twelve hours later, in Session 2, they were tested on their memory again. Stimuli consisted of 160 images from eight semantic categories and were strategically positioned on-screen to test the effects of generalization on retrieval (i.e., category-based memory distortions and biases). After the delay, retrieval was less accurate and demonstrated more generalization. However, these effects were mostly independent of Group, with some evidence for enhanced generalization following a period of wakefulness over sleep. Generalization was also driven by time of day, with more generalization in the evening relative to the morning. Taken together, our results, based on a large online sample, do not support a role for sleep in promoting memory generalization. Significance StatementBehavior is often guided by memories of previous experiences. However, for behavior to be adaptive and flexible (e.g., when encountering never-before-seen stimuli), regularities about the world must be extracted from these memories. This process, termed memory generalization, has been hypothesized to rely on sleep. We used a large online sample to test sleeps role in generalization and found no support for this hypothesis. Our results suggest that sleep and wakefulness contribute to generalization equally, with the latter potentially having a larger contribution.

neuroscience↗

bioRxiv2025

Concurrent presentation of memory-related odors and sounds nullified sleep reactivation benefits

AbstractReactivation of recently acquired memories during sleep supports their longevity. Reactivation can be altered during sleep using odors or sounds through a technique termed targeted memory reactivation (TMR). Here, we attempted to selectively weaken memories by reactivating them together with forgetting instructions. We delivered sounds to reactivate spatial memories and concurrent odors to reactivate instructions. Participants learned about the instructions in a Directed-Forgetting task performed with a list of to-be-remembered and to-be-forgotten words. One odor was linked with instructions to forget, one with instructions to remember, and a third was not assigned any meaning. During a nap, sounds previously linked with object-location learning were simultaneously presented with these odors. Spatial recall was tested after sleep. Sound cues produced a selective recall benefit for weakly encoded memories. However, memory results did not support the prediction that forgetting could be instilled by the concurrent forget odor. An encoding-strength-dependent benefit was largest when sounds were presented together with the odor that lacked assigned meaning, whereas the other two odors both disrupted sound-induced memory reactivation. These two odors were linked with instructions and with multiple learning episodes in the Directed-Forgetting task. Accordingly, we infer that reactivation evoked by the remember and forget odor cues interfered with the reactivation of spatial memories. Odors also induced a prolonged decline in sigma EEG power (12-16 Hz) that continued at least 10 s after odor offset. Overall, these findings highlight the complexity of memory consolidation during sleep when multiple memories and multiple cues are involved.

neuroscience↗

bioRxiv2023

The reach of reactivation: Effects of consciously-triggered versus unconsciously-triggered reactivation of associative memory

Newly formed memories are not passively stored for future retrieval; rather, they are reactivated offline and thereby strengthened and transformed. However, reactivation is not a uniform process: it occurs throughout different states of consciousness, including conscious rehearsal during wakefulness and unconscious processing during both wakefulness and sleep. In this study, we explore the consequences of reactivation during conscious and unconscious awake states. Forty-one participants learned associations consisting of adjective-object-position triads. Objects were clustered into distinct semantic groups (e.g., multiple fruits, vehicles, musical instruments) which allowed us to examine the consequences of reactivation on semantically-related memories. After an extensive learning phase, some triads were reactivated consciously, through cued retrieval, or unconsciously, through subliminal priming. In both conditions, the adjective was used as the cue. Reactivation impacted memory for the most distal association (i.e., the spatial position of associated objects) in a consciousness-dependent and memory-strength-dependent manner. First, conscious reactivation of a triad resulted in a weakening of other semantically related memories, but only those that were initially more accurate (i.e., memories with lower pre-reactivation spatial errors). This is similar to what has been previously demonstrated in studies employing retrieval-induced forgetting designs. Unconscious reactivation, on the other hand, benefited memory selectively for weak cued items. Semantically linked associations were not impaired, but rather integrated with the reactivated memory. Taken together, our results demonstrate that conscious and unconscious reactivation of memories during wakefulness have qualitatively different consequences on memory for distal associations. Effects are memory-strength-dependent, as has been shown for reactivation during sleep. Results support a consciousness-dependent inhibition account, according to which unconscious reactivation involves less inhibitory dynamics than conscious reactivation, thus allowing more liberal spread of activation. Our findings set the stage for additional exploration into the role of consciousness in memory structuring.

neuroscience↗

bioRxiv2022

Context matters: Changes in memory over a period of sleep are driven by encoding context

During sleep, recently acquired episodic memories (i.e., autobiographical memories for specific events) are strengthened and transformed, a process termed consolidation. These memories are contextual in nature, with details of specific features interwoven with more general properties such as the time and place of the event. In this study, we hypothesized that the context in which a memory is embedded would guide the process of consolidation during sleep. To test this idea, we employed a spatial memory task and considered changes in memory over a 10-hour period including either sleep or wake. In both conditions, participants (N = 62) formed stories that contextually bound four objects together, and then encoded the on-screen spatial position of all objects. Results showed that the changes in memory over the sleep period were correlated among contextually linked objects, whereas no such effect was identified for the wake group. These results suggest that contexts binding different memories together play an active role in consolidation during sleep.

neuroscience↗

bioRxiv2022

Made together, replayed together: Context reinstatement during sleep guides memory consolidation

New memories arent quarantined from each other when first encoded; rather, they are interlinked with memories that were encoded in temporal proximity or share semantic features. By selectively biasing memory processing during sleep, here we test whether context influences sleep-consolidation. Participants first formed 18 idiosyncratic narratives, each linking four objects together. Before sleep,they also memorized an on-screen position for each object. During sleep, 12 object-specific sounds were unobtrusively presented, thereby cuing the corresponding spatial memories and impacting spatial recall as a function of initial memory strength. As hypothesized, we find that recall for non-cued objects contextually linked with cued objects also changed. Post-cue electrophysiological responses suggest that activity in the sigma band supports context reinstatement and predicts context-related memory benefits. Concurrently, context-specific electrophysiological activity patterns emerge during sleep. We conclude that reactivation of individual memories during sleep evokes reinstatement of their context, thereby impacting consolidation of associated knowledge.

neuroscience↗

bioRxiv2018

Targeted memory reactivation during sleep to strengthen memory for arbitrary pairings

A powerful way to investigate memory consolidation during sleep utilizes acoustic stimulation to reactivate memories. In multiple studies, Targeted Memory Reactivation (TMR) using sounds associated with prior learning improved later memory, as in recalling locations where objects previously appeared. In the present experiment, we examined whether a variant of the same technique could strengthen memory for the locations of pairs of objects. Each sound was naturally connected to one object from each pair, but we hypothesized that both memories could be improved with TMR. We first asked participants to memorize each of 50 pairs of objects by associating the two objects with each other and with the sound of one of the objects (e.g., cat-meow). Next, objects were presented in unique locations on a grid. Participants learned these locations in an adaptive procedure. During an afternoon nap, 25 of the sounds were quietly presented. In memory tests given twice before and twice after the nap, participants heard the sound for each object pair and were asked to recall the name of the second object and the locations of both objects. Forgetting scores were calculated using the mean difference between pre-nap and post-nap spatial recall errors. We found less forgetting after the nap for cued compared to non-cued objects. Additionally, the extent of forgetting tended to be similar for the two members of each pair, but only for cued pairs. Results thus substantiate the potential for sounds to reactivate spatial memories during sleep and thereby improve subsequent recall performance, even for multiple objects associated with a single sound and when participants must learn a novel sound-object association.\n\nHighlightsO_LIMemories can be improved during sleep using arbitrary sounds\nC_LIO_LIParticipants learned a random screen location for each of 100 objects\nC_LIO_LIObjects were learned in pairs with the characteristic sound of one of the objects\nC_LIO_LIHalf of those sounds were presented during a nap that followed learning\nC_LIO_LIAfter sleep, location recall was more accurate for cued than for non-cued objects\nC_LI

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