Biology subjects

Cravo, A. M.

Publications and source records attributed to Cravo, A. M..

14 recordsLinked to original sources

bioRxiv2026

Separable Codes for Time and Decision in Human Temporal Perception

Time perception involves estimating physical durations and making categorical judgments relative to reference intervals. However, most studies conflate these processes, limiting insight into how they are encoded in brain activity. Here, we used EEG and multivariate pattern analysis (MVPA) to dissociate neural representations of time and decision during a temporal discrimination task. Thirty participants (humans of any sex) compared variable intervals to block-specific references, with duration and category (shorter, equal, or longer) manipulated orthogonally. Behaviorally, responses were shaped by target duration, category and recent trial history. An Internal Reference Model (IRM) indicated that participants dynamically updated their internal reference over trials. MVPA showed that both physical duration and categorical decision information were encoded throughout the trial, though with distinct temporal profiles. These signals were represented along separable neural dimensions, enabling their differentiation in brain activity. These findings suggest that time perception relies on parallel, functionally distinct processes for tracking duration and making temporal decisions, supporting models that treat them as independent components of temporal evaluation.

neuroscience↗

bioRxiv2025

Connectome Similarity Varies with Global Metastability and Movie Content

IntroductionRecent evidence supports that non-linear segments of brain activity carries most of the individual-specific information which allows unique identification based on functional connectomes (e.g. connectome fingerprints) in MEG. In fMRI, metastability has emerged as a reliable and robust summary measure of brain dynamics. Here, we set out to test the hypothesis that metastability is associated with connectome fingerprinting in naturalistic fMRI. We further examined whether this putative association varies with time scales, across brain functional networks, and depending on the movie content. MethodsWe analyzed fMRI data from 86 participants of the Naturalistic Neuroimaging Database. Data was collected during movie-watching of 10 entire movies of different genres. Global and network-level metastability were calculated using an fMRI-appropriate proxy measure based on the variability of spatial coherence. The within-subject stability (Iself) and between-subjects similarity (Iothers) of individual functional connectomes were also calculated. Linear mixed-effects models and appropriate contrasts were used to test associations between metastability and fingerprinting indices. ResultsAt the whole-brain level and considering data from all movies, an association across windows was found between metastability, Iself, and Iothers, with stronger effects observed for larger windows, such as the 600-second window (Iself: b = -0.13, SE = 0.032, p < 0.001; Iothers: b = -0.23, SE = 0.028, p < 0.001). Associations were also observed with distinct magnitudes within the eight large-scale functional networks, with particularly strong effects in the Motor Network (Iself: b = -0.34, SE = 0.027, p < 0.001; Iothers: b = -0.27, SE = 0.021, p < 0.001). Although no whole-brain differences were observed, movie content exhibited distinct association patterns within networks, notably for the prediction of Iself in the Visual Network for 500 Days of Summer ({Delta} = -0.22, SE = 0.11, p = 0.043). For Iothers, significant between-movie differences were found in the AMN ({Delta} = -0.25, SE = 0.062, p < 0.001), Dorsal Attention ({Delta} = 0.16, SE = 0.08, p = 0.038), Ventral Attention ({Delta} = 0.14, SE = 0.060, p = 0.017), and Visual Networks ({Delta} = -0.17, SE = 0.081, p = 0.031). ConclusionMetastability is systematically related to functional connectome fingerprints. This relationship is time-scale dependent, varies across functional networks, and is sensitive to movie content. Our findings bridge nonlinear brain dynamics and connectome identifiability, highlighting naturalistic paradigms as a powerful framework for individualized precision neuroimaging.

neuroscience↗

bioRxiv2025

Serial dependence during visuomotor integration is robust to the passage of time and interference from intervening tasks

When intercepting a moving target, responses are systematically biased toward the time of impact from the previous trial. This phenomenon, known as serial dependence, relies on a memory mechanism that remains poorly understood. In interceptive tasks, multiple stimulus features -- such as speed, time, or motor responses -- can guide behavior on the current trial and may be stored to influence subsequent trials. Here, we examined how memory decays over short inter-trial intervals (Experiment 1, N = 23) and whether interleaved tasks influence serial dependence (Experiment 2, N = 28). Participants performed either a temporal reproduction task or a speed judgment task, designed to compete for temporal and speed-processing resources, respectively. Our findings reveal that serial dependence persists across all inter-trial durations and remains unaffected by intervening tasks. While serial dependence was neither reduced nor eliminated, variations in responses were partially influenced by prior temporal reproductions from the interfering task. These results suggest that serial dependence in visuomotor tasks is robust to both the passage of time and external interference, though task responses may be subtly modulated by preceding temporal reproductions.

neuroscience↗

bioRxiv2023

Time for What? Dissociating Explicit Timing Tasks Through Electrophysiological Signatures

Estimating durations between hundreds of milliseconds and seconds is essential for several daily tasks. Explicit timing tasks, which require participants to estimate durations to make a comparison (time for perception) or to reproduce them (time for action), are often used to investigate psychological and neural timing mechanisms. Recent studies have proposed that mechanisms may depend on specific task requirements. In this study, we conducted electroencephalogram (EEG) recordings on human participants as they estimated intervals in different task contexts to investigate the extent to which timing mechanisms depend on the nature of the task. We compared the neural processing of identical visual reference stimuli in two different tasks, in which stimulus durations were either perceptually compared or motorically reproduced in separate experimental blocks. Using multivariate pattern analyses, we could successfully decode the duration and the task of reference stimuli. We found evidence for both overlapping timing mechanisms across tasks as well as recruitment of task-dependent processes for comparing intervals for different purposes. Our findings suggest both core and specialised timing functions are recruited to support explicit timing tasks.

neuroscience↗

bioRxiv2022

Temporal learning modulates post-interval ERPs in a categorization task with hidden reference durations.

The investigation of time-related activity in human electrophysiological activity has recently expanded from signals during the estimated interval to post-interval activity. Previous findings show timing-associated event-related potentials (ERPs) in both early ([~]150ms) and late positive components (LPC; [~]300ms) post-interval signals. However, it is still unclear whether and what aspects of temporal information these different patterns of EEG activity are capturing, especially, if these signals are associated with interval duration or other task parameters. In the present work, we designed a modified temporal categorization task to investigate if participants adaptation to a changing decisional context led to changes in post-interval ERPs. Participants had to learn a hidden reference duration on each block to categorize the presented target intervals correctly. We found an early posterior N200 potential correlated to target durations and decisional context. A central LPC, which interacted with duration and learning of the hidden reference, predicted behavioral responses. Our findings add to the current evidence that interval duration modulates post-interval activity in timing categorization tasks and shows that late signals are associated with interval duration and decisional context.

neuroscience↗

bioRxiv2020

Time-Encoding Migrates from Prefrontal Cortex to Dorsal Striatum During Learning of a Self-Timed Response Duration Task

Although time is a fundamental dimension of life, we do not know how the brain encodes the temporal information. Several brain areas underlie the temporal information, such as the hippocampus, prefrontal cortex, and striatum, but evidence of how they cooperate to process temporal information is scarce. Notably, the analysis of neural activity during learning are rare, mainly because timing tasks usually take a long time to train. Here we investigated how the time encoding evolves when animals learn to time a 1.5 s interval. We designed a novel training protocol where rats go from naive- to proficient-level timing performance within a single session, allowing us to investigate neuronal activity from very early learning stages. We used pharmacological experiments and machine-learning algorithms to evaluate the level of time encoding in the medial prefrontal cortex and the dorsal striatum. Our results show a double dissociation between the roles of the medial prefrontal cortex and the dorsal striatum during temporal learning, where the former commits to early learning stages while the latter become more engaged as animals become more proficient in the task.

neuroscience↗

bioRxiv2020

Temporal dynamics of implicit memory underlying serial dependence

Serial dependence is the effect in which the immediately preceding trial influences participants' responses to the current stimulus. But for how long does this bias last in the absence of interference from other stimuli? Here, we had 20 healthy young adult participants (12 women) perform a coincident timing task using different inter-trial intervals to characterize the serial dependence effect as the time between trials increases. Our results show that serial dependence abruptly decreases from 0.1 s to 1 s inter-trial interval, but it remains pronounced after that for up to 8 s. In addition, participants' response variability slightly decreases over longer intervals. We discuss these results in light of recent models suggesting that serial dependence might rely on a short-term memory trace kept through changes in synaptic weights, which might explain its long duration and apparent stability over time.

neuroscience↗

bioRxiv2020

Temporal prediction elicits rhythmic pre-activation of relevant sensory cortices

Being able to anticipate events before they happen facilitates stimulus processing. The anticipation of the contents of events is thought to be implemented by the elicitation of prestimulus templates in sensory cortex. In contrast, the anticipation of the timing of events is typically associated with entrainment of neural oscillations. It is so far unknown whether and in which conditions temporal expectations interact with feature-based expectations, and, consequently, whether entrainment modulates the generation of content-specific sensory templates. In this study, we investigated the role of temporal expectations in a sensory discrimination task. We presented participants with rhythmically interleaved visual and auditory streams of relevant and irrelevant stimuli while measuring neural activity using magnetoencephalography. We found no evidence that rhythmic stimulation induced prestimulus feature templates. However, we did observe clear anticipatory rhythmic pre-activation of the relevant sensory cortices. This oscillatory activity peaked at behaviourally relevant, in-phase, intervals. Our results suggest that temporal expectations about stimulus features do not behave similarly to explicitly cued, non-rhythmic, expectations; yet elicit a distinct form of modality-specific pre-activation. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=165 SRC="FIGDIR/small/347005v3_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@fce8corg.highwire.dtl.DTLVardef@1c16c3corg.highwire.dtl.DTLVardef@1a90d62org.highwire.dtl.DTLVardef@1adaa17_HPS_FORMAT_FIGEXP M_FIG C_FIG The brain extracts temporal regularities from the environment to anticipate upcoming events. Furthermore, with prior knowledge about their contents, the brain is thought to leverage this by instantiating anticipatory sensory templates. We investigated if sensory templates occur in response to a rhythmic stimulus stream with predictable temporal structure. We found that temporal rhythmic predictions did not induce sensory templates, but rather modulated the excitability in early sensory cortices.

neuroscience↗

bioRxiv2020

Task-Dependent Electrophysiological Signatures of Explicit Perceptual Timing

Studies investigating the neural mechanisms of time perception often measure brain activity while participants perform a temporal task. However, several of these studies are based exclusively on tasks in which time is relevant, making it hard to dissociate activity related to decisions about time from other task-related patterns. In the present study, human participants performed a temporal or color discrimination task of visual stimuli. Participants were informed which magnitude they would have to judge before or after presenting the two stimuli (S1 and S2) in different blocks. Our behavioral results showed, as expected, that performance was better when participants knew beforehand which magnitude they would judge. Electrophysiological data (EEG) was analyzed using Linear Discriminant Contrasts (LDC) and a Representational Similarity Analysis (RSA) approach to investigate whether and when information about time and color was encoded. During the presentation of S1, we did not find consistent differences in EEG activity as a function of the task. On the other hand, during S2, we found that temporal and color information was encoded in a task-relevant manner. Taken together, our results suggest that task goals strongly modulate decision-related information in EEG activity.

neuroscience↗

bioRxiv2020

Prestimulus alpha power is related to the strength of stimulus representation

Spatial attention can modulate behavioural performance and is associated with several electrophysiological markers. In this study, we used multivariate pattern analysis in electrophysiology data to investigate the effects of covert spatial attention on the quality of stimulus processing and underlying mechanisms. Our results show that covert spatial attention led to (i) an anticipatory alpha power desynchronization; (ii) enhanced stimuli identity information. Moreover, we found that alpha power fluctuations in anticipation of the relevant stimuli boosted and prolonged the coding of stimulus identity.

neuroscience↗

bioRxiv2019

Temporal regularity and stimulus control in multiple fixed interval schedules

In multiple fixed interval schedules of reinforcement, different time intervals are signaled by different environmental stimuli which acquire control over behavior. Previous work has shown that temporal performance is controlled not only by external stimuli but also by temporal aspects of the task, depending on the order in which the different intervals are trained - intermixed across trials or in blocks of several trials. The aim of this study was to further describe the training conditions under which the stimuli acquire control over temporal performance. We manipulated the number of consecutive trials of each fixed interval (FI) per training block (Experiment I) and the number of FIs trained (Experiment II). The results suggest that when trained in blocks of several consecutive trials of the same FI, temporal performance is controlled by temporal regularities across trials and not by the visual stimuli that signal the FIs. One possible account for those data is that the temporal cues overshadow the visual stimuli for the control of temporal performance. Similar results have also been observed with humans, which suggest that temporal regularity overcomes the stimuli in the control of behavior in temporal tasks across species.

animal behavior and cognition↗

bioRxiv2019

Dissociating decisional and temporal information in interval categorisation

Interval timing is fundamental for humans and non-human animals to interact with their environment. Several studies that investigate temporal processing combine behavioural tasks with neurophysiological methods, such as electrophysiological recordings (EEG). However, in the majority of these studies, it is hard to dissociate whether EEG activity reflects temporal or decisional information. In the present study, we investigated how time and decision is encoded in the EEG signal while human participants performed a temporal categorisation task with two different temporal references. Using a combination of evoked potentials and multivariate pattern analysis, we show that: (1) During the interval to-be-timed, both temporal and decisional information are encoded; (2) Activity evoked by the end of the interval encodes almost exclusively decisional information. These results suggest that decisional aspects of the task better explain EEG activity commonly related to temporal processing. The interplay between the encoding of time and decision is consistent with recent proposals that approximate temporal processing with decisional models.

neuroscience↗

bioRxiv2017

A common representation of time across visual andauditory modalities

Humans and non-human animals ability to process time on the scale of milliseconds and seconds is essential for adaptive behaviour. A central question of how brains keep track of time is how specific temporal information across different sensory modalities is. In the present study, we show that encoding of temporal intervals in auditory and visual modalities are qualitatively similar. Human participants were instructed to reproduce intervals in the range from 750 ms to 1500 ms marked by auditory or visual stimuli. Our behavioural results suggest that, although participants were more accurate in reproducing intervals marked by auditory stimuli, there was a strong correlation in performance between modalities. Using multivariate pattern analysis in scalp EEG, we show that activity during late periods of the intervals was similar within and between modalities. Critically, we show that a multivariate pattern classifier was able to accurately predict the elapsed interval, even when trained on an interval marked by a stimulus of a different sensory modality. Taken together, our results suggest that, while there are differences in the processing of intervals marked by auditory and visual stimuli, they also share a common neural representation.

neuroscience↗

bioRxiv2016

Temporal anticipation based on memory

The fundamental role that our long-term memories play in guiding perception is increasingly recognised, but the functional and neural mechanisms are just beginning to be explored. Though experimental approaches are being developed to investigate the influence of long-term memories on perception, these remain mostly static and neglect their temporal and dynamic nature. Here we show we show that our long-term memories can guide attention proactively and dynamically based on learned temporal associations. Across two experiments we found that detection and discrimination of targets appearing within previously learned contexts are enhanced when the timing of target appearance matches the learned temporal contingency. Neural markers of temporal preparation revealed that the learned temporal associations trigger specific temporal predictions. Our findings emphasize the ecological role that memories play in predicting and preparing perception of anticipated events, calling for revision of the usual conceptualisation of contextual associative memory as a reflective and retroactive function.

neuroscience↗