Biology subjects

Bramao, I.

Publications and source records attributed to Bramao, I..

4 recordsLinked to original sources

bioRxiv2025

Prior knowledge influences the neural mechanisms supporting memory-based inference

Memory allows us to go beyond direct experience by enabling inference across separate events. Yet how prior knowledge shapes the mechanisms supporting such inferences remains unclear. Here, we show that alignment between ongoing experience and existing knowledge determines how the brain constructs cross-event inferences. Behaviorally, inferences across schema-congruent events did not require accurate retrieval of the individual episodes, whereas inferences across schema-incongruent events depended on successful retrieval of those episodes. EEG-based multivariate pattern analysis further showed that schema-congruent inference was supported by schema reinstatement during encoding, consistent with the formation of integrated memory representations. In contrast, schema-incongruent inference relied on context-specific reinstatement at retrieval, reflecting the flexible recombination of distinct memories. Together, these findings demonstrate that prior knowledge dynamically shapes memory toward integration or separation, revealing how the brain constructs inferences to support flexible cognition.

neuroscience↗

bioRxiv2025

Episodic events are flexibility encoded in both integrated and separated neural representations

This study investigates how the brain encodes episodic events to support diverse memory functions. Thirty-six participants viewed movies simulating real-life interactions while EEG was recorded. They first watched movies featuring two characters (AB), followed by scenes where one original character interacted with a new one (BC). Memory was assessed for direct (AB and BC), indirect (AC) associations, and source memory about whether two characters had appeared together. Source memory was more accurate when participants correctly inferred indirect associations. Time-resolved representational similarity analysis (RSA) of EEG data revealed both neural pattern similarities and dissimilarities during AB and BC encoding. Pattern similarities, indicating memory integration across episodes, predicted successful indirect associations. Conversely, dissimilarities predicted accurate source memory, indicating the preservation of distinct memory traces. These findings suggest that episodic events are flexibly encoded through both integrated and segregated neural representations, enabling the brain to support multiple memory functions depending on task demands.

neuroscience↗

bioRxiv2025

Neural dynamics of relational memory retrieval across eye movements

Relational memory retrieval entails a dynamic interplay between eye movements and neural activity, yet the temporal coordination of these processes remains unclear. This study examines the relationship between theta and alpha EEG activity and sequential fixations during relational memory retrieval. Participants completed a two-alternative forced-choice associative memory task while their eye movements and EEG were recorded simultaneously. Results reveal a relational eye-movement effect: correctly remembered target elements were disproportionately fixated during later stages of the retrieval sequence. Time-frequency EEG analyses across the test trial show that successful retrieval was characterized by an early, transient increase in theta power and a sustained decrease in alpha power. Gaze-related analyses linked these effects to distinct retrieval processes. The theta effect emerged after the initial cue fixation and predicted retrieval success independently of whether subsequent saccades were directed to the target or distractor. In contrast, the alpha decrease predicted retrieval success only across continued target fixations. These findings connect the relational eye-movement effect to two distinct neural signatures: a nonspecific theta increase, reflecting recollection that may initiate pattern completion, and a target-selective alpha decrease, reflecting sustained reactivation of goal-relevant associations across fixations. Together, these results clarify the temporal dynamics of relational memory retrieval and underscore the role of sequential eye movements in memory-guided behavior.

neuroscience↗

bioRxiv2022

Episodic memory formation in naturalistic viewing

The brain systems of episodic memory and oculomotor control are tightly linked, suggesting a crucial role of eye movements in memory. But little is known about the neural mechanisms of memory formation across eye movements in unrestricted viewing behavior. Here, we leverage simultaneous eye tracking and EEG recording to examine episodic memory formation in free viewing. Participants memorized multi-element events while their EEG and eye movements were concurrently recorded. Each event comprised elements from three categories (face, object, place), with two exemplars from each category, in different locations on the screen. A subsequent associative memory test assessed participants memory for the between-category associations that specified each event. We used a deconvolution approach to overcome the problem of overlapping EEG responses to sequential saccades in free viewing. Brain activity was time-locked to the fixation onsets, and we examined EEG power in the theta and alpha frequency bands, the putative oscillatory correlates of episodic encoding mechanisms. Three modulations of fixation-related EEG predicted high subsequent memory performance: 1) theta increase at fixations after between-category gaze transitions, 2) theta and alpha increase at fixations after within-element gaze transitions, 3) alpha decrease at fixations after between-exemplar gaze transitions. Thus, event encoding with unrestricted viewing behavior was characterized by three neural mechanisms, manifested in fixation-locked theta and alpha EEG activity that rapidly turned on and off during the unfolding eye movement sequences. These three distinct neural mechanisms may be the essential building blocks that subserve the buildup of coherent episodic memories during unrestricted viewing behavior.

neuroscience↗