Biology subjects

Bavassi, L.

Publications and source records attributed to Bavassi, L..

5 recordsLinked to original sources

bioRxiv2025

Remoteness sensitive theta network dynamics during early autobiographical memory access

AO_SCPLOWBSTRACTC_SCPLOWAutobiographical memory (AM) is a crucial aspect of human cognition that aids in social understanding, decision-making, and future planning. Its inherent diversity provides a valuable framework for exploring the neural dynamics underlying the retrieval of memories of varying ages. This study aimed to determine whether the access phase of AM retrieval contains neural signatures sensitive to the remoteness of these memories. Forty-one participants engaged in an AM retrieval task while their brain activity was recorded using electroencephalography (EEG). We measured spectral power and time-resolved Granger Causality (GC) during the first 1500 ms following the onset of memory recovery. The results showed that remote autobiographical memories led to a significant increase in midline fronto-central theta power (6.5-8 Hz) around 900 ms after retrieval, compared to recent memories. Additionally, GC analyses revealed that both recent and remote memories showed an anterior-to-posterior flow of information, but the remote network present a denser and more efficient connectivity pattern in the theta band between 800 and 1100 milliseconds. These findings suggest that the remoteness of memories influences the early stages of autobiographical memory access. They also highlight theta power and its directed interactions as temporally precise markers of the neural mechanisms that support autobiographical memory retrieval.

animal behavior and cognition↗

bioRxiv2025

The hidden phase of memory: EEG signatures of reactivation during post-retrieval rest

AO_SCPLOWBSTRACTC_SCPLOWMemory retrieval reactivates previously encoded representations, allowing for their modification and strengthening. However, the neural processes that follow reactivation and contribute to long-term retention remain poorly understood. Here, we examined the post-retrieval resting period to identify neural markers of memory reactivation and their relation to subsequent memory performance. Participants learned pairs of nonsense syllables in multisensory contexts and, on the following day, received either a cue-syllable reminder (context + cue syllable; RX) or a context-only reminder (RCTX) while EEG activity was recorded before and after the reminder presentation. Both reminders elicited significant reductions in beta power (25-40 Hz) during the post-reminder rest, consistent with memory reactivation. The magnitude of beta decrement correlated with better long-term performance. Graph-theoretical analyses of phase synchronization networks in the beta band revealed that the RCTX reminder produced higher bilateral frontal betweenness centrality, suggesting greater engagement of frontal regions in mediating global information flow when retrieving only contextual cues. Moreover, frontal centrality and network density were predictive of subsequent memory accuracy. These findings demonstrate that memory reactivation extends beyond cue presentation into post-retrieval rest, leaving identifiable oscillatory and topological signatures that influence memory persistence. Our results underscore the crucial role of frontal network dynamics and beta-band activity in facilitating long-term memory.

neuroscience↗

bioRxiv2025

Reactivating aversive memories in humans: An EEG and Microstates study of post-retrieval processes

Although fear conditioning is one of the most widely used models to study anxiety in humans, much remains to be explored regarding its underlying neural correlates. In this study, we employed a three-day threat-conditioning protocol in which an angry face (conditioned stimulus, CS+) was paired with an aversive sound (unconditioned stimulus, US). Our main objective was to identify neural markers of post-retrieval processes triggered by the presentation of the CS+ alone, 24 hours after acquisition. We recorded resting-state electroencephalographic (EEG) activity before and after memory reactivation in two groups of participants (females and males counterbalanced): a Reactivation group previously exposed to threat conditioning on Day 1 (n=26) and a Control group (n=26) with no prior conditioning, focusing on memory-related patterns in the frequency domain and microstate dynamics. Our results confirmed successful conditioning and memory retention 48 hours later, as evidenced by implicit, declarative, and emotional responses. Regarding neural activity, we found lower beta-band activity (25-30 Hz) in central brain regions after reactivation, which may reflect enhanced post-reactivation processing of the threat conditioning memory, in contrast to participants who viewed the stimulus for the first time. We observed changes in microstates and a potential link between microstate C and conditioned threat memory. These findings provide initial evidence for neural correlates of post-retrieval processes of an implicit threat memory offering potential relevance for understanding mechanisms implicated in anxiety and related disorders.

neuroscience↗

bioRxiv2023

Segregation-to-Integration Transformation (SIT) Model of Memory Evolution

AO_SCPLOWBSTRACTC_SCPLOWMemories are thought to use coding schemes that dynamically adjust their representational structure to maximize both persistence and utility. However, the nature of these coding scheme adjustments and their impact on the temporal evolution of memory after initial encoding is unclear. Here we introduce the Segregation-to-Integration Transformation (SIT) Model, a neural network formalization that offers a unified account of how the representational structure of a memory is transformed over time. SIT Model asserts that memories initially adopt a highly modular or segregated network structure, functioning as an optimal storage buffer by striking a balance between protection from disruptions and accommodating substantial information. Over time, a repeated combination of neural network reactivations, spreading, and synaptic plasticity transforms the initial modular memory structure into an integrated memory form, facilitating intercommunity spreading and fostering generalization. In addition, SIT Model reveals the existence of an optimal window during this transformation where memories are most susceptible to malleability, suggesting a non-linear or inverted U-shaped function in memory evolution. The results of our model integrate a wide range of experimental phenomena along with accounts of memory consolidation and reconsolidation, offering a unique perspective on memory evolution by leveraging simple architectural neural network property rules.

neuroscience↗

bioRxiv2020

A working memory intervention weakens the reconsolidation of a threat memory and its biases processing towards threat.

BACKGROUNDThreat-conditioning (TC) memory plays a central role in anxiety disorders, but not in a simple way. This memory impacts on complex cognitive systems by modifying behavioral responses with a bias to fearful stimuli and overestimating potential threats. In this study we proposed a global approach analyzing the scope of disrupting TC memory reconsolidation in the implicit memory, the declarative contingency and the cognitive biases. METHODSDay 1: Subjects were trained on TC. Day 2: after Threat-memory reactivation, one group performed a high demanding working memory task (HWM) and the other a low demanding working memory task (LWM). The last group, only performed the HWM task. Day 3: TC memory was tested by an extinction session followed by reinstatement. Finally, all subjects completed tasks targeting stimuli representation, valuation and attentional bias towards threat. RESULTSDisrupting reconsolidation of TC memory with a HWM weakened the implicit memory retention and faded the representation and valuation towards threat but it had no effect on attentional bias. Moreover, we revealed that subjects performance during the working memory task was specifically associated in TC memory retention. CONCLUSIONSOur findings reveal a strong impairment of the threat-memory restabilization and associated emotional biases. This may result from the competition between defensive survival and central-executive control networks. Our results fits with Experimental Psychopathology approach, disentangling the relation between the implicit memory, cognitive, valenced systems and the possibility to weaken both the threatening memory and the systems associated with the maintenance of anxiety profile.

neuroscience↗