Biology subjects

Romei, V.

Publications and source records attributed to Romei, V..

15 recordsLinked to original sources

bioRxiv2026

The aging rhythm: spatio-temporal dynamics of resting alpha oscillations in young and older brains

Aging is associated with substantial alterations in brain oscillatory activity, particularly within the alpha band (8-12 Hz). Yet, little is known about how aging affects the spatial propagation of alpha oscillations across cortical networks. In addition, although previous EEG studies have consistently reported age-related slowing of alpha peak frequency and changes in alpha power, the interpretation of these findings remains debated because oscillatory measures are influenced by age-related modifications in the aperiodic component of the power spectrum. Here, we investigated age-related changes in both the spectral and spatiotemporal properties of alpha activity using resting-state EEG data from a large cohort of younger (N = 326) and older adults (N = 108). To address the debate in the literature, analyses explicitly accounted for the aperiodic component of the EEG power spectrum. Consistent with previous literature, older adults exhibited a robust slowing of the individual alpha peak frequency, along with reductions in the aperiodic exponent and offset. Importantly, alpha-band power was also significantly reduced in older adults even after correcting for aperiodic activity, indicating that age-related alpha alterations cannot be fully explained by non-oscillatory spectral changes alone. Beyond conventional spectral measures, we characterized alpha-band traveling waves and identified age-related alterations in their propagation dynamics, particularly within frontal regions. Older adults showed enhanced medial-to-lateral and interhemispheric propagation patterns, suggesting reduced hemispheric segregation and increased bilateral coordination of rhythmic activity. These findings extend current models of cognitive aging by demonstrating that aging affects not only the spectral characteristics of alpha oscillations but also their large-scale spatiotemporal organization. Together, the results support the view that aging involves a functional reorganization of cortical communication dynamics, potentially reflecting compensatory mechanisms within distributed neural networks.

neuroscience↗

bioRxiv2026

Reduced Backward Alpha Propagation at Rest Marks the Autism Continuum

Autism spectrum disorder and subclinical variation along the autism continuum are characterized by in sensory processing and cognitive integration, phenomena increasingly linked to atypical large-scale communication across cortical hierarchies. While structural and functional connectivity differences have been extensively documented, whether autistic traits are associated with a reorganization of the directional properties of ongoing cortical activity remains less understood. Here, we recorded resting-state EEG from 201 young adults selected from the lower and upper terciles of the Autism Quotient distribution and analyzed traveling-wave dynamics over parieto-frontal lines. Individuals with higher autistic traits showed a selective shift in left-hemisphere alpha-band traveling-wave directionality, driven primarily by reduced backward-dominant propagation and accompanied by a reciprocal shift toward forward dominance. This effect was anatomically specific, absent in an occipito-central control line set, and not accompanied by a matching pattern of group differences in oscillatory power, aperiodic spectral parameters, or peak alpha frequency. These findings identify resting-state alpha traveling waves as a candidate physiological signature of altered directional organization across the autism continuum, with potential relevance as a trait-sensitive neural marker.

neuroscience↗

bioRxiv2026

The confidence code: parietal alpha oscillations turn expectations into beliefs

Metacognition, the ability to evaluate whether ones decisions are correct, is crucial for adaptive behavior. However, confidence judgments are not bias-free: they can be systematically modulated by predictive cues and beliefs, favoring expectation-consistent judgments, while leaving metacognitive precision unchanged. Here, we identify parietal alpha activity as the causal mechanism linking expectations to metacognitive bias. In Study 1, EEG was recorded while 75 participants performed a visual detection task with symbolic cues signaling target probability. Cues induced a metacognitive bias in confidence without altering metacognitive sensitivity, and cue-driven alpha modulation over the right parietal cortex predicted the magnitude of this bias. In Study 2 (N = 88), continuous theta-burst stimulation (cTBS) over the right parietal cortex abolished cue-induced alpha modulation, thereby selectively reducing metacognitive bias, while sham stimulation had no effect. Together, these findings demonstrate that parietal alpha-mediated gain control causally shapes metacognitive judgments, revealing an oscillatory code for predictive metacognition.

neuroscience↗

bioRxiv2026

Autistic Traits are Associated with Suboptimal Decision Bias Strategies in Subsecond Timing

Time perception difficulties are frequently reported in Autism Spectrum Disorder, yet empirical findings remain inconsistent. A key methodological limitation is the failure to separate perceptual sensitivity from decision-making strategies. We applied Signal Detection Theory (SDT) to a subsecond duration discrimination task (100 and 500 ms) in 65 non-clinical adults varying in autistic traits, assessed via the Autism-Spectrum Quotient (AQ) and a Principal Component Analysis (PCA) of its subscales. Autistic traits did not predict reduced perceptual sensitivity (d'): temporal discrimination remained intact across the full autism-trait continuum, with Bayesian analyses providing converging evidence against a perceptual deficit. Instead, a PCA-derived cognitive component -- combining heightened Attention to Detail with reduced Imagination -- was systematically associated with a shift in decision bias (c). Individuals with this profile showed a graded attenuation of standard-based anchoring, with ordinal position progressively filling the gap. This shift operated consistently across both temporal scales, as confirmed by trial-level generalized linear mixed modelling, and reflects a quantitative redistribution of anchoring weight rather than a categorical switch in strategy. These findings reframe temporal "rigidity" in ASD not as a perceptual deficit, but as a suboptimal yet internally consistent decision-making style favouring within-trial information over accumulated representational knowledge. Lay AbstractMany autistic people report difficulties with time in daily life, but scientists have long disagreed on whether this reflects a genuine perceptual problem. This study found that autistic traits do not impair the basic ability to judge duration. Instead, people with more autistic traits tend to rely on which event came first, rather than accumulating experience across trials to refine their judgments -- a less effective but internally consistent strategy.

developmental biology↗

bioRxiv2026

Aging redirects prior expectations from perception to action

Aging profoundly reshapes how the brain integrates sensory evidence with prior expectations during perceptual decision-making. Combin ing behavioural modelling with high-density EEG, we show that older adults assign greater weight on prior information, resulting in stronger decisional bias and reduced sensory precision under probabilistic cues. Neural dynamics revealed a breakdown of anticipatory tuning in visual alpha rhythms, supporting sensory preparation in youth, alongside enhanced central beta activity, indicating a shift toward pre-emptive motor engagement aligned with expected responses. A data-driven decomposition further showed that, whereas prior-driven behaviour in younger adults emerges from a flexible interplay between sensory and executive oscillatory systems, it becomes dominated in aging by a rigid, response-centred mode. Together, these findings uncover a large-scale reconfiguration of predictive computations with age, marking a transition from adaptive sensory-executive coordination to a more automatized, action-oriented predictive strategy.

neuroscience↗

bioRxiv2025

Targeted Neuromodulation of Perceptual Decision-Making Networks Causally Dissociates Sensory and Metacognitive performance

Perceptual judgements and their subjective evaluation (i.e., metacognition) are considered tightly coupled aspects of decision-making. Yet, emerging evidence suggests that distinct neural mechanisms underlie these processes. In motion perception, studies have identified a neural network involving visual and associative parietal areas supporting these abilities. Whilst early (V1/V2) and specialized (V5/MT+) visual areas are associated with motion discrimination accuracy, the intraparietal sulcus (IPS/LIP) plays a critical role in the formation of subjective confidence for sensory decision, given its functionally coupling with the V5/MT+-V1/V2 network. Previous studies have consistently reported that increasing connectivity in the human V5/MT+-to-V1/V2 pathway by means of cortico-cortical paired associative stimulation (ccPAS) - a neurostimulation protocol inducing Hebbian-like changes in neuronal pathways - improves our perceptual ability to discriminate motion. Notably, we recently demonstrated that strengthening V5/MT+ influence over V1/V2 also leads to overconfidence - altering metacognitive bias for motion discrimination, suggesting that the manipulation of V5/MT+-V1/V2 network might functionally affect IPS/LIP activity. Here, we directly investigated this possibility by first strengthening the V5/MT+-V1 pathway with ccPAS, and subsequently interfering with IPS/LIP activity by means of continuous theta-burst stimulation (cTBS). In line with previous evidence, our results corroborate that enhancing V5/MT+-V1/V2 connectivity affects both motion discrimination and metacognitive bias. Crucially, IPS/LIP disruption through cTBS selectively affects metacognitive performance while leaving motion discrimination unaltered. These findings highlight distinct neural substrates for perceptual sensitivity and visual metacognition linked to V5/MT+ and IPS/LIP, respectively, opening to potential tailored applications of non-invasive brain stimulation (NIBS) to functionally improve sensory and metacognitive decision-making processes.

neuroscience↗

bioRxiv2025

Predictive inference alterations in psychosis proneness are context-dependent

BackgroundPerception depends on the dynamic integration of sensory inputs and prior expectations, shaped by recent experience. While disruptions in this inferential process have been proposed as core features of psychosis, whether such alterations can be observed in subclinical psychosis-like experiences (PLEs), and how they manifest across different forms of perceptual inference remains unclear. MethodsTwo independent samples of healthy adults participated in the study: 80 completed a visual detection task, and 62 performed a motion discrimination task. Data were analysed using mixed-effects models with a continuous PLE measure and supplemented by categorical comparisons between the lowest- and highest-PLEs terciles. ResultsPLEs predicted reduced sensitivity to sensory evidence and increased reliance on probabilistic cues across both tasks. Critically, history biases diverged across contexts. In the detection task, a repulsive bias from the previous stimulus was observed in the overall sample, but this effect was attenuated in high-PLEs. In contrast, in the discrimination task, high-PLEs exhibited a repulsive bias away from their previous choice, reversing the typical repetition tendency seen in low-PLEs. ConclusionsOur results suggest that psychosis-like traits alter how prior expectations interact with sensory input and recent perceptual history. High-PLEs showed reduced influence of recent sensory input in detection task, consistent with altered low-level adaptation. In contrast, in the discrimination task, they showed a shift away from previous choices, suggesting disruption of decision-level integration of past choices. This points to a task-dependent instability in the use of past information, reflecting a broader inferential vulnerability linked to the psychosis spectrum.

neuroscience↗

bioRxiv2025

Backward alpha oscillations shape perceptual bias under probabilistic cues

Predictive coding theory suggests that prior knowledge is crucial for optimizing human decision-making, with recent studies emphasizing the role of alpha-band oscillations in this process. Here, we employed a traveling waves approach to investigate how alpha oscillations integrate prior expectations during a perceptual decision-making task. Our findings demonstrated that expectation-based knowledge triggers the propagation of alpha traveling waves from frontal to occipital areas, with this increase associated with enhanced modulation of brain regions involved in stimulus processing and directly linked to prior-driven bias at the behavioral level. Moreover, participants who relied more on prior expectations exhibited stronger top-down signaling, whereas those who focused on sensory input showed a contrasting forward signaling pattern. These results highlight the role of alpha-band traveling waves in predictive mechanisms, suggesting that rhythmic interactions across brain regions facilitate this process and contribute to inter-individual differences in its implementation.

neuroscience↗

bioRxiv2024

Preparing to act follows Bayesian inference rules

Predictive brain theories suggest that human brain sets-up predictive models to anticipate incoming sensory evidence. Recent studies demonstrated these models to be integrated already in sensory areas, shaping even perceptual outcomes. Here, we hypothesized that this integration process informs the entire functional hierarchy, thus scaling all the way down to the motor system. Operationally, we propose that cue-oriented cortico-spinal excitability (CSE) modulation serves the pre-activation of motor representations aligned to prior-congruent decisions. To this end, 62 participants completed a probabilistic discrimination task while we delivered bilateral single-pulse TMS over the two primary motor cortices (M1s) and recorded motor-evoked potentials (MEPs) to assess motor excitability associated to prior-congruent vs. incongruent actions separately encoded by the two hands. Our findings revealed that prior expectations shaped CSE well before action execution, predominantly by inhibiting the M1 cortex coding for the prior-incongruent action. Importantly, this physiological modulation underpinned the prior-induced bias in participants choices, highlighting the link between motor preparatory modulation and actual decision-making. Furthermore, we observed significant interindividual variability in prior-driven CSE modulations, revealing two distinct predictive strategies: the believers style, who heavily rely on prior, and the empiricists one, who downplay its role, maintaining CSE level mostly unbiased. Crucially, autistic and schizotypal traits drove these differences in prior-driven motor strategy, with believers characterized by schizotypal traits, whereas empiricists displaying autistic-like features. These results demonstrate how predictive models are integrated into action representations and highlight the role of prior-driven CSE modulations as a potential marker able to intercept interindividual differences in predictive styles.

neuroscience↗

bioRxiv2024

Excitation/Inhibition imbalance impairs multisensory causal inference by increasing the proneness to experience the sound-induced flash illusion in the schizophrenia spectrum

The spectrum of schizophrenia is characterised by an altered sense of self with known impairments in tactile sensitivity, proprioception, body-self boundaries, and self-recognition. These are thought to be produced by failures in multisensory integration mechanisms, commonly observed as enlarged temporal binding windows during audiovisual illusion tasks. To our knowledge, there is an absence of computational explanations for multisensory integration deficits in patients with schizophrenia and individuals with high schizotypy, particularly at the neurobiological level. We implemented a multisensory causal inference network to reproduce the responses of individuals who scored low in schizotypy in a simulated double flash illusion task. Next, we explored the effects of recurrent excitation, cross-modal and feedback weights, and synaptic density on the visual illusory responses of the network. Using quantitative fitting to empirical data, we found that an increase in the weights of the recurrent excitatory connectivity in the network enlarges the temporal binding window and increases the overall proneness to experience the illusion, matching the responses of individuals scoring high in schizotypy. Moreover, we found that an increase in excitation increases the probability of inferring a common cause from the stimuli. We propose an E/I imbalance account of reduced temporal discrimination in the SCZ spectrum and discuss possible links with Bayesian theories of schizophrenia. We highlight the importance of adopting a multisensory causal inference perspective to address body-related symptomatology of schizophrenia.

neuroscience↗

bioRxiv2024

Top-down and bottom-up interactions rely on nested brain oscillations.

Adaptive visual processing is enabled through the dynamic interplay between top-down and bottom-up (feedback/feedforward) information exchange, presumably propagated through brain oscillations. Here we causally tested for the oscillatory mechanisms governing this interaction in the visual system. Using concurrent TMS-EEG, we emulated top-down signals by a single TMS-pulse over the Frontal Eye Field (right-FEF), while manipulating the strength of sensory input through the presentation of moving concentric gratings (compared to a control-TMS site). FEF-TMS without sensory input led to a top-down controlled occipital phase-realignment, alongside higher fronto-occipital phase-connectivity, in the alpha/beta-band. Sensory input in the absence of FEF-TMS increased occipital gamma activity. Crucially, testing the interaction between top-down and bottom-up processes (FEF-TMS during sensory input) revealed an increased nesting of the bottom-up gamma activity in the alpha/beta-band cycles. This establishes a causal link between phase-to-power coupling and top-down modulation of feedforward signals, providing novel mechanistic insights into how attention interacts with sensory input at the neural level, shaping rhythmic sampling.

neuroscience↗

bioRxiv2023

Alpha-band frequency and temporal windows in perception: A review andmeta-analysis of 25 experiments

Temporal windows in perception refer to windows of time within which distinct stimuli interact to influence perception. A simple example is two temporally proximal stimuli fusing into a single percept. It has long been hypothesized that the human alpha rhythm (an 8-13 Hz neural oscillation maximal over posterior cortex) is linked to temporal windows, with higher frequencies corresponding to shorter windows and finer-grained temporal resolution. This hypothesis has garnered support from studies demonstrating a correlation between individual differences in alpha frequency (IAF) and behavioral measures of temporal processing. However, non-significant effects have also been reported. Here, we review and meta-analyze 27 experiments correlating IAF with measures of visual and audio-visual temporal processing. Our results estimate the true correlation in the population to be between 0.39 to 0.53, a medium-to-large effect. The effect held when considering visual or audio-visual experiments separately, when examining different IAF estimation protocols (i.e., eyes-open and eyes-closed), and when using analysis choices that favor a null result. Our review shows that 1) effects have been internally and independently replicated 2) several positive effects are based on larger sample sizes than the null effects and 3) many reported null effects are actually in the direction predicted by the hypothesis. A free interactive web-app was developed to allow users to replicate our meta-analysis and change or update the study selection at will, making this a "living" meta-analysis (https://randfxmeta.streamlit.app). We discuss possible factors underlying null reports, design recommendations, and open questions for future research

neuroscience↗

bioRxiv2023

Strengthening connectivity between premotor and motor cortex increases inter-areal communication in the human brain

The ventral premotor cortex (PMv) is an important component of cortico-cortical pathways mediating prefrontal control over primary motor cortex (M1) function. Paired associative stimulation (ccPAS) is known to change PMv influence over M1 in humans, which manifests differently depending on the behavioural context. Here we show that these changes in influence are functionally linked to PMv-M1 phase synchrony changes induced by repeated paired stimulation of the two areas. PMv-to-M1 ccPAS leads to increased phase synchrony in alpha and beta bands while reversed order M1-to-PMv ccPAS leads to decreased theta phase synchrony. These changes are visible at rest but they are predictive of changes in oscillatory power in the same frequencies during movement execution and inhibition, respectively. The results unveil a link between the physiology of the motor network and the resonant frequencies mediating its interactions, and provide a putative mechanism underpinning the relationship between synaptic efficacy and brain oscillations.

neuroscience↗

bioRxiv2019

Assessing the specificity of the relationship between brain alpha oscillations and tonic pain

Recent research has pointed to alpha brain oscillations as a potential clinical biomarker for sensitivity to pain. In particular, researchers claimed that the slowing of individual alpha frequency (IAF) could be an objective marker of pain during prolonged nociceptive stimulation. However, prolonged pain has been also associated with increased IAF. To date, there is insufficient evidence to conclude that IAF can be a neural marker of pain.\n\nThe current study aimed at elucidating the conflicting findings by assessing the specificity of the relationship between brain alpha oscillations and tonic pain. We recorded electroencephalography (EEG) on healthy volunteers during exposure to consecutive 5-minute sessions of painful hot water immersion, innocuous warm water immersion and an aversive, non-painful auditory stimulus, matched by unpleasantness to the painful condition. Participants rated stimulus unpleasantness throughout each condition. We also asked participants to sit still with eyes closed and eyes open right before and after the three experimental conditions in order to obtain a robust estimate of baseline alpha. Our findings revealed both increased and decreased IAF during tonic hot stimulation depending on the alpha range targeted (7-13 Hz vs. 8-10 Hz). In addition, they provide mild evidence for a negative relationship between IAF and the unpleasantness of the experience. Finally, we could not identify a difference between IAF during tonic hot temperature and during tonic auditory experience. Altogether, these findings emphasize a twofold frequency pattern (increase vs. decrease) for IAF during tonic thermal pain, thus indicating the need for robust methodological scrutiny of IAF as a neural marker of pain.

neuroscience↗

bioRxiv2018

Spatial frequency tuning of perceptual learning and transfer in global motion

Perceptual learning is typically highly specific to the stimuli and task used during training. However, recently it has been shown that training on global motion can transfer to untrained tasks, reflecting the generalising properties of mechanisms at this level of processing. We investigated a) if feedback was required for learning when using an equivalent noise global motion coherence task, and b) the transfer across spatial frequency of training on a global motion coherence task, and the transfer of this training to a measure of contrast sensitivity. For our first experiment two groups, with and without feedback, trained for ten days on a broadband global motion coherence task. Results indicated that feedback was a requirement for learning. For the second experiment training consisted of five days of direction discrimination on one of three global motion tasks (broadband, low or high frequency random-dot Gabors), with trial-by-trial auditory feedback. A pre- and post-training assessment was also conducted, consisting of all three types of global motion stimuli (without feedback) and high and low spatial frequency contrast sensitivity. We predicted that if learning and transfer is cortically localised, then transfer would show specificity to the area processing the task (global motion). In this case, we would predict a broad transfer between spatial frequency conditions of global motion only. However, if transfer occurred as a result of backward generalisation, a more selective transfer would occur matching the low-pass broadband tuning of the area processing global motion. Our training paradigm was successful at eliciting improvement in the trained tasks over the five days. However, post-training transfer to trained or untrained tasks was only reported for the low spatial frequency trained group. This group exhibited increased sensitivity to low spatial frequency contrast, and an improvement for the broadband global motion condition. Our findings suggest that the feedback projections from global to local stages of processing play a role in transfer.

neuroscience↗