Biology subjects

Fuentemilla, L.

Publications and source records attributed to Fuentemilla, L..

16 recordsLinked to original sources

bioRxiv2026

Hippocampal and cortical oscillations support the encoding of event memories during movie watching

Remembering temporally-extended experiences requires integrating information over time into coherent event representations that can be stored and later retrieved. Oscillatory dynamics may provide a flexible mechanism to support these operations by coordinating communication across regions and organizing neural activity in time. Yet most evidence for the oscillatory basis of episodic encoding comes from discrete-stimulus paradigms, leaving unclear whether these mechanisms can help organize memory during continuous experience. Using iEEG recorded while participants watched a 50-min film, we measured how power, synchrony and phase alignment support memory formation at the beginning, middle, and end of the events. At event onset, remembered events showed reduced gamma power with increased hippocampal-frontal synchrony, indicating that successful events begin with transient long-range coordination rather than heightened local processing. Within an event, memory was predicted by the direction of change, with recalled events showing increases in temporal gamma power and hippocampal-temporal gamma synchrony, consistent with the progressive binding of incoming information into a developing event representation. At the end of an event, memory was supported by an increase in hippocampal theta power and phase resetting. Temporal gamma power was likewise elevated and hippocampal-temporal gamma synchrony increased, suggesting that information bound locally over the course of the event might be transmitted to the hippocampus as the event closes. Frontal beta power decreased at the same moment, consistent with disruption of the outgoing event model. Naturalistic memory formation therefore does not rest on a sustained encoding state, but on the appropriate temporal coordination and stability of oscillatory states across brain regions and event phases, in which stable oscillatory states support ongoing representation while transient, boundary-driven reorganization of hippocampal-cortical networks switches the system between consolidating the completed event and encoding the next.

neuroscience↗

bioRxiv2026

Metacognitive Efficiency Reduces Confirmation Bias in Perceptual Decision Making

Humans exhibit a pervasive drive toward self-consistency, often failing to revise previous decisions even when confronted with contradictory evidence. Here, we investigate the computational mechanisms underlying decision revision in perceptual tasks, examining the regulatory role of metacognition. To do so, we capitalize on a novel paradigm in which participants are repeatedly presented with identical sensory information and allowed to revise their choices after each exposure. Our results reveal that repeated exposure to the same stimulus systematically biases subsequent judgments toward prior responses. Using drift-diffusion modeling, we tested competing explanations incorporating different assumptions about how prior choices affect evidence accumulation. Our findings indicate that consistency biases emerge from asymmetric sensory weighting, selectively amplifying information consistent with previous choices--a phenomenon akin to confirmation bias. Crucially, individuals with higher metacognitive skills exhibited weaker confirmatory biases and more flexible integration of repeated sensory information, enabling greater adaptability in decision-making. These findings highlight the continuous nature of perceptual inference and underscore metacognitions pivotal role in mitigating bias and optimizing decision flexibility.

neuroscience↗

bioRxiv2025

Attention and Explicit Knowledge Drive Predictive Sharpening in Early Visual Cortex

Perception is increasingly understood as an inferential process, whereby what we perceive results from the integration of sensory inputs with expectations derived from prior knowledge. Top-down predictions have been shown to alter the encoding of sensory information, from early to late stages of processing. Yet, how such predictions shape neural representations in sensory cortices remains debated. Competing accounts suggest that predictions either sharpen neural representations by enhancing selectivity or dampen activity by broadly suppressing stimulus-driven responses. In a preregistered fMRI study, we tested whether these effects depend on the level of attentional engagement and explicit knowledge of predictive associations. Using a multisensory fMRI paradigm with concurrent but independent visual and auditory probabilistic associations (75% validity) and manipulated attention, we investigated predictive effects in human early visual cortex. Consistent with prior work, expected visual stimuli elicited reduced BOLD activity. Critically, sharpening of expected visual stimuli occurred exclusively when visual inputs were attended and the concurrently presented auditory inputs expected. In addition, the magnitude of the sharpening of visual representations correlated positively with participants explicit knowledge of the visuo-predictive associations. These findings highlight the key roles of attention and explicit knowledge in promoting predictive sharpening and underscore the need to study predictive processing in more ecologically valid, multisensory contexts.

neuroscience↗

bioRxiv2024

Odor-induced persistent neural activity in associativeencoding in humans

This study explored the impact of brief exposure to odor cues on sustained neural activity during a 6-second delay period before memory encoding of a picture image. Combining univariate and multivariate ERP analytical approaches, our results align with nonhuman data, indicating that odor cues induced sustained neural activity in humans, persisting beyond the odor exposure throughout the nearly 6-second delay period. We observed higher amplitude of sustained ERPs for unpleasant compared to pleasant odor cues. Additionally, participants exhibited more confident memory recall for pictures preceded by unpleasant rather than pleasant odor cues during encoding, underscoring the influence of brief odor cues on memory formation for temporally distant events. In conclusion, this study revealed that brief exposure to odor cues induced sustained neural activity in humans, with distinct effects on memory formation along the pleasantness dimension, emphasizing the lasting impact of olfactory stimuli on cognitive processes.

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↗

bioRxiv2023

Neocortico-hippocampal ripple-based coordination during naturalistic encoding

Ripples are fast oscillatory events widely recognized as crucial markers for memory consolidation and neural plasticity. These transient bursts of activity are thought to coordinate information transfer between the hippocampus and neocortical areas, providing a temporal framework that supports the stabilization and integration of new memories. However, their role in human memory encoding during naturalistic scenarios remains unexplored. Here, we recorded intracranial electrophysiological data from ten epilepsy patients watching a movie. Ripples were analyzed in the hippocampus and in neocortical regions (i.e., temporal and frontal cortex). Our results revealed a differential dynamical pattern of ripple occurrence during encoding. Enhanced hippocampal ripple recruitment was observed at event boundaries, reflecting hippocampal involvement in event segmentation, whereas higher ripple rates were seen within an event for cortical electrodes with higher ripple occurrence at the temporal cortex reflecting weather an event was later recalled. These findings shed light on the neural mechanisms underlying memory encoding and provide insights into the potential role of ripples in the encoding of an event, suggesting an impact in the formation of long-term memories of distinct episodes.

neuroscience↗

bioRxiv2023

Measuring phase-amplitude coupling opposition in neurophysiological signals with the Mean Opposition Vector Index (MOVI)

BackgroundThe phase-amplitude coupling (PAC) opposition between distinct neural oscillations is critical to understanding brain functions. Available methods to assess phase-preference differences between conditions rely on density of occurrences. Other methods like the Kullback-Leibler Divergence (DKL) assess the distance between two conditions by transforming neurophysiological data into probabilistic distributions of phase-preference and assessing the distance between them. However, these methods have limitations such as susceptibility to noise and bias. New MethodWe propose the "Mean Opposition Vector Index" (MOVI), a parameter-free, data-driven algorithm for unbiased estimation of PAC opposition. MOVI establishes a unified framework that integrates the strength of PAC to account for reliable unimodal differences in phase-specific amplitude coupling between neurophysiological datasets. ResultsWe found that MOVI accurately detected phase opposition, was resistant to noise and gave consistent results with low or asymmetrical number of trials, therefore in conditions more similar to experimental studies. Comparison with existing methodsMOVI outperformed Jensen-Shannon Divergence (JSD), an adaptation of the DKL, in terms of sensitivity, specificity, and accuracy to detect phase opposition. ConclusionsMOVI provides a novel and useful approach to study of phase-preference opposition in neurophysiological datasets.

neuroscience↗

bioRxiv2022

Distinct encoding and post-encoding representational formats contribute to episodic sequence memory formation

In episodic encoding, an unfolding experience is rapidly transformed into a memory representation that binds separate episodic elements into a memory form to be later recollected. However, it is unclear how brain activity changes over time to accommodate the encoding of incoming information. This study aimed to investigate the dynamics of the representational format that contributed to memory formation of sequential episodes. We combined Representational Similarity Analysis and multivariate decoding approaches on EEG data to compare whether "category-level" or "item-level" representations supported memory formation during the online encoding of a picture triplet sequence and offline, in the period that immediately followed encoding. The findings revealed a gradual integration of category-level representation during the online encoding of the picture sequence and a rapid item-based neural reactivation of the encoded sequence at the episodic offset. However, we found that only memory reinstatement at episodic offset was associated with successful memory retrieval from long term memory. These results suggest that post-encoding memory reinstatement is crucial for the rapid formation of unique memory for episodes that unfold over time. Overall, the study sheds light on the dynamics of representational format changes that take place during the formation of episodic memories.

neuroscience↗

bioRxiv2022

Contextual incongruency triggers memory reinstatement and the disruption of neural stability

Schemas, or internal representation models of the environment, are thought to be central in organising our everyday life behaviour by giving stability and predictiveness to the structure of the world. However, when an element from an unfolding event mismatches the schema-derived expectations, the coherent narrative is interrupted and an update to the current event model representation is required. Here, we asked whether the perceived incongruence of an item from an unfolding event and its impact on memory relied on the disruption of neural stability patterns preceded by the neural reactivation of the memory representations of the just-encoded event. Our study includes data from 3 different experiments whereby participants encoded images of target objects preceded by trial-unique sequences of events depicting daily routine. We found that neural stability patterns gradually increased throughout the ongoing exposure to a schema-consistent episodic narrative and that the brain stability pattern was interrupted when the encoding of an object of the event was lowly congruent within the ongoing schema representation. We found that the decrease in neural stability for low-congruence items was best seen at [~]1000 ms from object encoding onset when compared to high-congruence items and that this effect was preceded by an enhanced N400 ERP and an increased degree of neural reactivation of the just-encoded episode for low-congruence items. Current results offer new insights into the neural mechanisms and their temporal orchestration that are engaged during online encoding of schema-consistent episodic narratives and the detection of incongruencies.

neuroscience↗

bioRxiv2021

Post-encoding reactivation promotes one-shot learning of episodes in humans

Prior animal and human work have shown that post-encoding reinstatement plays an important role in organizing the temporal sequence of unfolding episodes in memory. Here, we investigated whether post-encoding reinstatement serves to promote the encoding of one-shot episodic learning beyond the temporal structure in humans. In experiment 1, participants encoded sequences of pictures depicting unique and meaningful episodic-like events. We used representational similarity analysis on scalp electroencephalography recordings during encoding and found evidence of rapid picture elicited EEG patterns reinstatement at episodic offset (around 500ms post-episode). Memory reinstatement was not observed between successive elements within an episode and the degree of memory reinstatement at episodic offset predicted later recall for that episode. In experiment 2, participants encoded a shuffled version of the picture sequences from experiment 1, rendering each episode meaningless to the participant but temporally structured as in experiment 1, and we found no evidence of memory reinstatement at episodic offset. These results suggest that post-encoding memory reinstatement is akin to the rapid formation of unique and meaningful episodes that unfold over time.

neuroscience↗

bioRxiv2020

Evidence of shifts towards neural states of stability during the retrieval of real-life episodic memories

How does one retrieve real-life episodic memories? Here, we tested the hypothesis, derived from computational models, that successful retrieval relies on neural dynamics patterns that rapidly shift towards stable states. We implemented cross-temporal correlation analysis of electroencephalographic (EEG) recordings while participants retrieved episodic memories cued by pictures collected with a wearable camera depicting real-life episodes taking place at "home" and at "the office". We found that the retrieval of real-life episodic memories is supported by rapid shift towards brain states of stable activity, that the degree of neural stability is associated with the participants ability to recollect the episodic content cued by the picture, and that each individual elicits stable EEG patterns that were not shared with other participants. These results indicate that the retrieval of autobiographical memory episodes is supported by rapid shifts of neural activity towards stable states.

neuroscience↗

bioRxiv2020

Neurophysiological signatures in the retrieval of individual autobiographical memories of real-life episodic events

Autobiographical memory (AM) refers to recollected events that belong to an individuals past. In a classical episodic retrieval experiment in a laboratory, the events to be remembered are words or pictures that have hardly any personal relevance. While such stimuli provide necessary experimental and controlled conditions helping to advance in the understanding of memory, they do not capture the whole complexity of real-world stimuli. Recently, the incorporation of wearable cameras has allowed us to study the cognitive and neural bases of AM retrieval without active participant involvement, and they have been demonstrated to elicit a strong sense of first-person episodic recollection enhancing ecological validity. Here, we provide a new approach to understanding the retrieval of personal events, implementing a convolution network-based algorithm for the selection of the stimuli while monitoring participants memory retrieval with scalp EEG recordings over three periods of time after encoding (1 week, 2 weeks, and 6 to 12 months). We also examined an individual with a condition termed Aphantasia that provided more insights into the sensitivity of our protocol in the investigation of individual AM using real-life sequences.

neuroscience↗

bioRxiv2019

Theta rhythm supports hippocampus-dependent integrative encoding in schematic memory networks

Integrating new information into existing schematic structures of knowledge is the basis of learning in our everyday life activity as it enables structured representation of information and goal-directed behaviour in an ever-changing environment. However, how schematic mnemonic structures aid the integration of novel elements remains poorly understood. Here, we showed that the ability to integrate novel picture information into learn structures of picture associations that overlap by the same picture scene (associative network) or by the conceptually related scene information (schematic network) is hippocampus-dependent, as patients with lesions at the medial temporal lobe (including the hippocampus) were impaired in inferring novel relations between elements within these mnemonic networks but not in retrieving individual pictures in a subsequent memory test. In addition, we observed more persistent and widespread scalp electroencephalographic (EEG) theta oscillatory pattern (3-6Hz) while healthy participants encoded novel pictures related to schematic memory networks, suggesting that theta may reflect distances between elements within a representational network space. Finally, we found high similarity values for neural activity patterns elicited by novel and related events only within associative networks, thereby suggesting that neural reactivation may promote the integration of new information into existing memory networks only when direct associations within the network link their elements. These findings have important implications for our understanding of the neural mechanisms that support the development and organization of structures of knowledge.

neuroscience↗

bioRxiv2019

Rapid memory reactivation at movie event boundaries promotes episodic encoding

Segmentation of continuous experience into discrete events is driven by rapid fluctuations in encoding stability at context shifts (i.e., event boundaries), yet the mechanisms underlying the online formation of event memories are poorly understood. We investigated the neural spatiotemporal similarity patterns of the scalp electrophysiological (EEG) activity of 30 participants watching a 50 min movie and found that event boundaries triggered rapid reinstatement of the just-encoded movie event EEG patterns. We also found that the onset of memory reinstatement at boundary onset (around 1500ms) was preceded by an N400-like ERP component, which likely reflects the detection of a context switch between the current and just-encoded event. A data-driven approach based on Hidden Markov Modeling allowed us to detect event boundaries as shifts between stable patterns of brain EEG activity during encoding and identify their reactivation during a free recall task. These results provide the first neurophysiological underpinnings for how the memory system segments a continuous stream of experience into episodic events.

neuroscience↗

bioRxiv2018

Implicit but not explicit exposure to threat conditioned stimulus prevents spontaneous recovery of threat potentiated startle responses in humans

It has long been posited that threat learning operates and forms under an affective and a cognitive learning system that are supported by different brain circuits. A primary drawback in exposure-based therapies is the high rate of relapse when higher order inhibitory structures failed to inhibit the emotional responses driven by the defensive circuit. It has been shown that implicit exposure of fearful stimuli leads to a long-lasting reduction of avoidance behavior in patients with phobia through the facilitation of fear processing areas in the absence of subjective fear. Despite the potential benefits of this approach in the treatment of phobias and PTSD, implicit exposure to fearful stimuli is still under-investigated. Here, we used unconscious presentation of threat-conditioned stimuli in healthy humans, using a continuous flash suppression technique. We found that implicit exposure of a conditioned stimulus reduced, on the following day, defensive responses to the conditioned stimulus measured by threat-potentiated startle responses but not by the electrodermal activity. Our results suggest that implicit exposure using CFS might facilitate the modulation of the affective component of fearful memories, representing an important therapeutic target to further advance exposure-based psychotherapies.

animal behavior and cognition↗

bioRxiv2018

Age-related impairment of semantic integration into long-term memory is related to theta-alpha and low beta oscillations

Long-term memory can improve when incoming information is congruent with known semantic information. This so-called congruence effect has widely been shown in younger adults but age-related changes and neural mechanisms remain unclear. Here, congruence improved recognition memory in younger and older adults (i.e. congruency effect), but - importantly - this effect decreased with age. Electroencephalography data show that, in both groups, congruence led to widespread differences in event-related potentials (ERPs) and alpha-beta oscillations (8-30 Hz), known to support semantic processing. Importantly, these ERP differences predicted increases in memory performance, especially for congruent items. Finally, age-related differences in memory were accompanied by a positive ERP and later decrease in theta-alpha (5-13 Hz) during encoding, which were greater in the younger group. Together, although semantic congruence generally increases long-term memory, the effect is less pronounced in the elderly. At the neural level, theta-alpha oscillations, previously linked to memory and attentional processes, provide a mechanistic explanation for such an age-related effect.

neuroscience↗