Biology subjects

Tarasi, L.

Publications and source records attributed to Tarasi, L..

10 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

Strengthening interhemispheric connectivity increases interregional information transfer between human primary motor areas

Communication between brain regions is thought to be supported by the temporal alignment of their oscillatory activity creating rhythmic windows of opportunity for efficient information transfer. We examined this possibility by manipulating the strength of coupling between the left primary motor cortex (lM1) and the right primary motor cortex (rM1) and examined the impact on activity transfer between the two areas measurable in the electroencephalogram (EEG) in 60 right-handed individuals. In three experiments we manipulated the strength of the pathway connecting the lM1 and rM1 by applying paired associative stimulation (ccPAS) using three different patterns, two of which increase interregional coupling strength. We measured the impact on EEG communication transfer in the alpha, beta, and theta bands at rest. Augmenting the strength of the lM1-to-rM1 pathway enhanced the interregional communication volume in the high-theta/low alpha band, and both volume and speed in the beta band, respectively. These changes, visible at rest, are related to changes in the transcallosal inhibitory influence of the lM1 over rM1 cortical excitability following ccPAS. By contrast, augmenting the rM1-to-lM1 route failed to modulate communication transfer in right-handed individuals. The results provide direct evidence of oscillatory intra-areal information transfer, demonstrating a link between motor network physiology and the resonant frequencies mediating its interactions.

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↗