Biology subjects

Bola, M.

Publications and source records attributed to Bola, M..

4 recordsLinked to original sources

bioRxiv2026

When the psychedelic state's over: limited evidence for persistent neurophysiological changes in naturalistic psychedelic users

BackgroundContemporary research indicates that psychedelics induce notable neurophysiological changes, some lasting weeks to months after a single dose. However, most evidence derives from acute administration studies and limited post-acute follow-ups. Long-term naturalistic psychedelic users remain critically underexamined, yet may exhibit distinct neurobiological profiles informing our understanding of persistent alterations following repeated exposure. MethodsWe recorded resting-state EEG in 57 long-term psychedelic users (abstinent [≥]30 days) and 49 matched non-users across two independent sites under eyes-open and eyes-closed conditions. We analyzed oscillatory power, signal complexity, and source-localized effective connectivity, focusing on five canonical frequency bands and regions of the Default Mode, Salience, and Central Executive Networks. Analyses included linear mixed-effects modeling for power spectra and complexity results and a rank-based approach combining ordinary least squares regression with randomization inference for effective connectivity. ResultsWe observed predominantly null findings. No significant between-group differences emerged for oscillatory power. Complexity comparison yielded results contrary to our hypothesis: psychedelic users exhibited lower complexity values in the eyes-open condition. Effective connectivity revealed no within- or between-network differences that would survive statistical corrections. Additionally, we report a few small-magnitude effects uncovered by exploratory analyses. Conclusions Long-term naturalistic psychedelic users showed largely non-significant differences in oscillatory power, complexity, and network connectivity compared to non-users -- across several measures commonly reported as altered in acute administration studies. These findings raise the question of whether psychedelics neurophysiological signatures persist during abstinence despite repeated prior use, or whether they reflect homeostatic receptor adaptation, individual variability, or contextual factors. Null, incongruous, or subtle effects contribute to the existing evidence base, yet underscore the need for replication in larger, more ecologically valid populations to advance the emerging field of psychedelic neuroscience.

neuroscience↗

bioRxiv2020

Complex naturalistic stimuli capture attention automatically when maintained in working memory

Recent studies suggest that a stimulus actively maintained in working memory (WM) automatically captures visual attention when subsequently perceived. Such a WM-guidance effect has been consistently observed for stimuli defined by simple features, such as colour or orientation, but studies using more complex stimuli provide inconclusive results. Therefore, we investigated whether the WM-guidance effect occurs also for naturalistic stimuli, whose identity is defined by multiple features and relations among them, specifically for faces and houses. The experiment consisted of multiple blocks in which participants (N = 28) either memorized or merely saw (WM or exposure condition, respectively) a template stimulus and then performed several dot-probe trials, with pairs of stimuli (template and control) presented laterally as distractors and followed by a target-asterisk. Evidence for attentional prioritization of the memorized stimuli was found in the reaction-times (RT) analysis, but not in the analysis of the N2pc ERP component, which raises questions concerning the attentional mechanism involved. Further, in an exploratory ERP analysis we found evidence for a very early (100-200 ms post-stimulus) prioritization specific to the memorized faces, which is in line with the sensory recruitment theory of WM.

neuroscience↗

bioRxiv2020

The self-face automatically captures attention without consciousness

It is well established that stimuli representing or associated with ourselves, like our own name or an image of our own face, benefit from preferential processing. However, two key questions concerning the self-prioritization mechanism remain to be addressed. First, does it operate in an automatic manner during the early processing, or rather in a more controlled fashion at later processing stages? Second, is it specific to the self-related stimuli, or can it be activated also by other stimuli that are familiar or salient? We conducted a dot-probe experiment to investigate the mechanism behind attentional prioritization of the selfface image and to tackle both questions. The former, by employing a backwards masking procedure to isolate the early and preconscious processing stages. The latter, by investigating whether a face that becomes visually familiar due to repeated presentations is able to capture attention in a similar manner as the self-face. Analysis of the N2pc ERP component revealed that the self-face image automatically captures attention, both when processed consciously and unconsciously. In contrast, the visually familiar face did not attract attention, neither in the conscious, nor in the unconscious condition. We conclude that the selfprioritization mechanism is early and automatic, and is not triggered by a mere visual familiarity. More generally, our results provide further evidence for efficient unconscious processing of faces, and for a dissociation between attention and consciousness.

neuroscience↗

bioRxiv2018

EEG signal diversity reflects capability for behavioral responsiveness during propofol sedation

Transitions between wakefulness and anesthesia are accompanied by profound changes in brain functioning. A key challenge is thus to disentangle neuronal mechanisms specific to loss and recovery of consciousness, from more general effects that are not directly related to the capacity for conscious experience. Measures of neuronal diversity have been recently proposed to constitute a robust correlate of the global states of consciousness. In the present study we investigated whether EEG signal diversity is indeed related to behavioral responsiveness during propofol sedation, or rather to the general drug-related effects. To this end, we reanalyzed data collected from 20 subjects sedated with propofol. Based on the responsiveness to auditory stimuli all subjects were subdivided into two subgroups - responsive (n = 13), who remains awake throughout the experiment, and drowsy (n = 7), who becomes unresponsive during moderate sedation. Resting state EEG recorded during wakefulness and sedation was characterized by the Mean Information Gain (MIG) and Fluctuation complexity (FC) - information-theory measures estimating signal diversity or complexity, respectively. The main finding is that the drowsy group exhibited a decrease in diversity during sedation but, unexpectedly, the responsive group exhibited a robust increase in diversity (ANOVA group x state interaction: F(3) = 7.81, p < 0.001; BF10 > 197). However, signal complexity neither differentiated the subgroups, nor decreased reliably during sedation (t-test wake vs. moderate sedation: t(19) = 2.57, p = 0.092; BF10 = 3.08). Further, we show that a change in signal diversity is negatively correlated with a delta power change (r = -0.62, p = 0.002), and positively correlated with a beta power change (r = 0.84, p < 0.001). Finally, we show that MIG behaves in a qualitatively similar manner to Lempel-Ziv - another diversity measures used in several recent studies. Overall, we revealed that propofol sedation is initially related to an increase in EEG signal diversity, and that only upon loss of responsiveness EEG diversity decreases. The qualitatively different pattern of changes in the responsive and drowsy groups makes EEG diversity a robust indirect index of responsiveness and, presumably, consciousness.

neuroscience↗