Biology subjects

Sacchet, M. D.

Publications and source records attributed to Sacchet, M. D..

10 recordsLinked to original sources

bioRxiv2026

EEG brain reconfiguration during meditation-induced extended cessation of consciousness: A dense-sampling multi-participant microstate study

Extended cessation (EC) is a rare, non-ordinary meditative endpoint characterized by a temporary absence of reportable phenomenal experience, followed by an extraordinary perceptual vividness, openness, equanimity and affective balance. EC thus offers a unique, non-pharmacological window into the brain dynamics underlying suspension of conscious experience and the subsequent psychological transformations. The present study investigated whole-brain electrophysiological changes induced by EC using a dense-sampling electroencephalographic microstate analysis, in five highly trained meditators. Temporal parameters and transition probabilities of canonical microstates during EC were compared with two control conditions (counting and memory tasks) across six frequency bands (broadband, delta, theta, alpha, beta, gamma). EC was characterized by alterations in global explained variance and coverage of microstates B and C, both associated with self-referential processing. Specifically, EC involved less frequent and shorter occurrences of microstate B, and more frequent and longer occurrences of microstate C. Transition probabilities also reconfigured: transitions from A and B to C increased, whereas transitions from A to B decreased. These broadband effects were distributed across delta, theta, and beta frequency sub-bands. Additional band-specific changes emerged for microstate A and D. Delta band showed longer microstate A and increased B-to-A transitions during EC, while beta band showed less frequent and shorter D and decreased bidirectional B-to-D transitions. These scalp-level findings support a precision re-weighting account of EC, reflecting self-referential reconfigurations with enhanced sensory-anchored inflow. This study provides initial evidence for the neurophysiological correlates of EC, with potential implications for human wellbeing. SIGNIFICANCE STATEMENTExtended cessation is a rare meditative state involving a voluntarily, temporary suspension of conscious experience, offering an exceptional opportunity to study how the brain supports and disrupts conscious awareness without pharmacological intervention. By applying EEG microstate analysis, this study identifies distinct large-scale neural reconfigurations during EC, particularly within microstates linked to self-referential processing. These findings suggest that EC involves a dynamic redistribution of precision and sensory-anchored processing, providing initial neurophysiological evidence for how advanced meditation may reshape conscious experience. This work advances the scientific understanding of non-ordinary states of consciousness and highlights their potential relevance for human well-being.

neuroscience↗

bioRxiv2025

The neuroscience of highly stable, positive, and refined states of consciousness during jhana-type advanced concentration absorption meditation (ACAM-J)

Humans can experience a rich array of conscious experience, including highly stable, positive, and refined states of non-ordinary perception that can be elicited through advanced meditation. Here, we present the first group-level, ultra-high-field (7T) fMRI study of jhana advanced concentration absorption meditation (ACAM-J). We combined local (regional homogeneity), mesoscale (connectivity gradients), and global (geometric eigenmodes) human brain mapping with diverse and detailed phenomenology, meditative traits, behaviorally assessed cognitive functions, and extensive publicly available psychobehavioral affinity maps. Across eight successive states of ACAM-J, we observed reproducible neural trajectories marked by anterior-to-posterior reorganization, flattening of cortical hierarchies, nonlinear reconfiguration of global harmonics, and tight coupling between brain metrics and equanimity, attentional stability, and behavior. Neurosynth decoding further associate ACAM-J with reduced suffering-related processes and more with attentional monitoring. These findings suggest ACAM-J is a distinct, structured mode of awareness that persists despite radically reduced narrative thought and sensory content. Our findings also inform boundary conditions for current models of consciousness. More broadly, this research indicates that advanced meditation is a powerful framework for understanding psychological transformation, and for potential new opportunities for supporting human well-being and flourishing.

neuroscience↗

bioRxiv2025

Whole-Brain Models of Minimal Phenomenal Experience: Approaching Criticality through Jhana Meditation

Advanced meditation offers a powerful lens for investigating consciousness and for understanding how sustained training may contribute to human flourishing. In the spirit of neurophenomenology, we combine first-person reports with model-free empirical analyses and formal whole-brain modeling to investigate the mechanisms underlying advanced meditative states and minimal phenomenal experience (MPE). Specifically, we focus on jh[a]na meditation, a type of advanced concentrative absorption meditation (ACAM-J). Advanced practitioners accessed the eight ACAM-J states during ultra-high-field 7T functional magnetic resonance imaging. For each state, we first characterize empirical functional connectivity and then build a mechanistic whole-brain model that reproduces brain activity by modeling the dynamical regimes of different brain networks. We found that the later ACAM-J states, taken here as candidates for MPE, show increased large-scale functional integration and a shift of functional network dynamics toward near-critical working points. The default mode network (DMN) exhibits the largest shift, from a distant noise-driven regime during the control condition to near-critical dynamics during ACAM-J. We also observed that the trajectory of ACAM-J states is non-linear, with prominent reconfigurations at key meditative milestones. Our results suggest that MPE, as instantiated in later ACAM-J states, corresponds to a globally susceptible state where near-critical dynamics dominate. We interpret this near-critical regime as a form of "openness", in which constrained and differentiated patterns of brain activity give way to greater flexibility. In particular, increased DMN susceptibility is correlated with broader attention and reduced narrative thought, consistent with a more flexible mode of self-related processing. In this context, advanced meditation provides a powerful model for studying how sustained contemplative practice can profoundly shape brain dynamics and provide a window into core aspects of consciousness.

neuroscience↗

bioRxiv2025

Neuroelectrophysiological correlates of extended cessation of consciousness in advanced meditators: A multimodal EEG and MEG study

In some contemplative traditions, "extended cessation" (EC) refers to a state of advanced meditation in which the meditator intentionally suppresses their own consciousness and re-emerges with a profound sense of clarity and equanimity. Here, we present the first electrophysiological study of EC, in which five meditators underwent concurrent electroencephalography (EEG) and magnetoencephalography (MEG) recording. EC significantly reduced alpha power. EC also tended to increase neural complexity, unlike other states in which consciousness is absent (e.g., sleep, anesthesia, disorders of consciousness). Our results indicate that the neural correlates of EC are distinct from other states that induce loss of consciousness and that complexity is not a sufficient condition for consciousness, while also providing new insights into the implications of advanced meditation for human flourishing.

neuroscience↗

bioRxiv2025

Endogenous suspension and reset of consciousness: 7T fMRI brain mapping of the extended cessation meditative endpoint

Extended cessation (EC), an advanced meditative state in which consciousness is volitionally suspended and later reset with immense mental clarity, equanimity, and peace, offers an endogenous model for investigating the mechanisms of consciousness. Using ultra-high-resolution 7T fMRI with dense within-subject sampling (N=3), we quantified whole-brain activity, functional and effective connectivity, cortical gradients, and eigenmodes, and related them to chemoarchitecture and cognitive maps. EC is marked by increased activity in unimodal regions, down-regulation in transmodal regions, subcortex, and brainstem, an expansion of the principal gradient, and decrease in low-order global eigenmodes. Cognitive decoding linked EC to heightened perceptual clarity and attention, least with mental suffering, and co-varied with histaminergic H receptors topology. These findings challenge predictions of Global Neuronal Workspace and Integrated Information Theory, while supporting the Active Inference Framework. More broadly, EC demonstrates that consciousness can cease without global suppression, suggesting a potential "reset" mechanism that fosters equanimity and the potential for flourishing.

neuroscience↗

bioRxiv2024

Integrated phenomenology and brain connectivity demonstrate changes in nonlinear processing in jhana advanced meditation

We present a neurophenomenological case study investigating distinct neural connectivity regimes during an advanced concentrative absorption meditation called jhana (ACAM-J),characterized by highly-stable attention and mental absorption. Using EEG recordings and phenomenological ratings (29 sessions) from a meditator with +20,000 hours of practice, we evaluated connectivity metrics tracking distinct large-scale neural interactions: nonlinear (WSMI and Directed Information), capturing non-oscillatory dynamics; and linear (WPLI) connectivity metrics, capturing oscillatory synchrony. Results demonstrate ACAM-J are better distinguished by non-oscillatory compared to oscillatory dynamics across multiple frequency ranges. Furthermore, combining attention-related phenomenological ratings with WSMI improves Bayesian decoding of ACAM-J compared to neural metrics alone. Crucially, deeper ACAM-J indicate an equalization of feedback and feedforward processes, suggesting a balance of internally- and externally-driven information processing. The results from this intensively sampled case study are a promising initial step in revealing the distinct neural dynamics during ACAM-J, offering insights into refined conscious states and highlighting the value of nonlinear neurophenomenological approaches to studying attentional states.

neuroscience↗

bioRxiv2024

High-precision neurofeedback-guided meditation training optimises real-world self-guided meditation practice for well-being

Meditation can benefit well-being and mental health, but novices often struggle to effectively recognize and disengage from mental processes during meditation due to limited awareness, potentially diminishing meditations benefits. We investigated whether personalised high-precision neurofeedback (NF) can improve disengagement from mental activity during meditation and enhance meditations outcomes. In a single-blind, controlled, longitudinal paradigm, 40 novice meditators underwent two consecutive days of meditation training with intermittent visual feedback from either their own (N=20) or a matched participants (N=20; control group) posterior cingulate cortex (PCC) activity measured using 7 Tesla functional magnetic resonance imaging. During training, the experimental group showed stronger functional decoupling of PCC from dorsolateral prefrontal cortex, indicating better control over disengagement from mental processes during meditation. This led to greater improvements in emotional well-being and mindful awareness of mental processes during a week of real-world self-guided meditation. We provide compelling evidence supporting the utility of high-precision NF-guided meditation training to optimise real-world meditation practice for well-being.

neuroscience↗

bioRxiv2021

High frequency rTMS modulates functional connectivity nodes and boundaries differently in the human brain

Repetitive transcranial magnetic stimulation (rTMS) has gained considerable importance in the treatment of neuropsychiatric disorders, including major depression. However, it is not yet understood how rTMS alters brains functional connectivity. Here we report changes in functional connectivity captured by resting state functional magnetic resonance imaging (rsfMRI) within the first hour after 10Hz rTMS. We apply subject-specific parcellation schemes to detect changes (1) in network nodes, where the strongest functional connectivity of regions is observed, and (2) in network boundaries, where functional transitions between regions occur. We use support vector machines (SVM), a widely used machine learning algorithm that is robust and effective for the classification and characterization of time intervals of changes in node and boundary maps. Our results reveal that changes in connectivity at the boundaries are slower and more complex than in those observed in the nodes, but of similar magnitude according to accuracy confidence intervals. These results were strongest in the posterior cingulate cortex and precuneus. As network boundaries are indeed under-investigated in comparison to nodes in connectomics research, our results highlight their contribution to functional adjustments to rTMS.

neuroscience↗

bioRxiv2019

Decoupling of Dopamine Release and Neural Activity in Major Depressive Disorder during Reward Processing Assessed by Simultaneous fPET-fMRI

The interaction of the midbrain dopaminergic system and the striatum is implicated in reward processing; it is still unknown, however, how this interaction is altered in Major Depressive Disorder (MDD). In the current study, we related the dopamine release/binding inferred by [11C] Raclopride functional Positron Emission Tomography (fPET) to neural activity monitored by blood-oxygen-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) in adults diagnosed with MDD and healthy controls (CTL). Participants completed a monetary incentive delay (MID) task during simultaneous [11C] Raclopride fPET and fMRI. Instead of the usual kinetic modeling method for analyzing dynamic PET time activity curves (TACs), we used a simpler general linear model (GLM) approach, which includes introducing a fPET dopamine activation response function to model changes in the TAC associated with the MID task. In addition, using simulations, we show that the GLM approach has several advantages over kinetic modeling. This is achieved without invoking erroneous steady-state assumptions or selecting a suitable reference region. Our results include the observation of both decreased fMRI activation and dopamine release/binding in the striatum in the MDD cohort, implying a reduced reward processing capacity in MDD. Furthermore, in the MDD group, individuals with lower fMRI activations in the right middle putamen and ventral medial prefrontal cortex (vmPFC) had higher reflection rumination scores, and individuals with lower dopamine release/binding in the left putamen and the right nucleus accumbens (NAcc) also had higher reflection rumination scores. Significant cross-modal inter-subject and intra-subject correlations of dopamine release/binding and fMRI activation were observed in the CTL group, but not in the MDD group. The intra-subject correlation of the two modalities was negatively associated with reflection rumination scores in the CTL group, indicating that decoupling of the dopaminergic system and striatum may be important in the pathophysiology of MDD.

neuroscience↗

bioRxiv2019

Subcortical Shape Alterations in Major Depressive Disorder: Findings from the ENIGMA Major Depressive Disorder Working Group

Alterations in regional subcortical brain volumes have been widely investigated as part of the efforts of an international consortium, ENIGMA, to determine reliable structural brain signatures for Major Depressive Disorder (MDD). Given that subcortical structures are comprised of distinct subfields, we sought to build significantly from prior work to precisely map localized MDD-related differences in subcortical regions using shape analysis. In this meta-analysis of subcortical shape from the ENIGMA-MDD working group, we compared 1,781 patients with MDD and 2,953 healthy controls (CTL) on individual measures of shape metrics (thickness and surface area) on the surface of seven bilateral subcortical structures: nucleus accumbens, amygdala, caudate, hippocampus, pallidum, putamen, and thalamus. Harmonized data processing and statistical analyses were conducted locally at each site, and findings were aggregated by meta-analysis. Relative to CTL, patients with MDD had lower surface area in the subiculum of the hippocampus, the basolateral amygdala, and the nucleus accumbens shell. Relative to CTL, patients with adolescent-onset MDD ([≤] 21 years) had lower thickness and surface area of the subiculum of the hippocampus and the basolateral amygdala. Relative to first-episode MDD, recurrent MDD patients had lower thickness and surface area in the CA1 of the hippocampus and the basolateral amygdala. Our results suggest that previously reported MDD-associated volumetric differences may be localized to specific subfields of these structures that have been shown to be sensitive to the effects of stress, with important implications for mapping treatments to patients based on specific neural targets and key clinical features.

neuroscience↗