Biology subjects

Buch, V.

Publications and source records attributed to Buch, V..

7 recordsLinked to original sources

bioRxiv2025

Distinct neural temporal architectures encode rapid social expressions and sustained internal mood states

Affective processing operates across multiple temporal scales, from rapid social signaling through facial expressions to sustained internal mood states, yet the neural computational principles governing these different timescales remain unclear. Understanding how the brain implements distinct temporal architectures for momentary versus persistent affective phenomena is important to comprehending emotional processing and developing objective biomarkers for psychiatric conditions. Here, we introduced a multimodal approach combining automated facial expression monitoring and continuous intracranial electroencephalography in 2,037 electrode contacts across 16 epilepsy patients, over multiple days. Of these, 15 and 12 patients met criteria for facial expression and for mood analysis, respectively. Among patients meeting criteria, we captured 1,396 naturalistic smiles, and 3,746 neutral expressions - separated by at least 10 seconds, alongside 336 periodic mood assessments. This paradigm revealed distinct behavioral and neural computational architectures. Aperiodic neural activity in the lateral temporal cortex (79.5% accuracy) encoded facial expressions with high cross-participant generalizability. Mood states, however, showed different encoding patterns. Facial expressions provided no consistent mood indicators across participants. Critically, low-gamma power dynamics in limbic regions encoded mood states in only a subset of individuals (5 of 12 participants) with expression-mood behavioral correlations, suggesting a distinct encoding phenotype. Cross-domain analysis confirmed computational independence: neural features optimized for facial expression decoding failed to predict sustained mood states, and vice versa. These findings suggest that multiple neural mechanisms may influence underlying affective processing, with variations in their contributions between individuals. The results provide a framework for understanding individual differences in neural mood representation and establish methodological approaches for objective measurement of naturalistic affective behaviors.

neuroscience↗

bioRxiv2025

Experience-Dependent Plasticity of Thalamoprefrontal Circuitry Characterizes Learning Across Species

Learning is an adaptive process which is thought to require precise coordination among multiple brain regions over time. Thalamoprefrontal circuitry is central to multiple domains of cognitive control and executive function, yet its evolution during learning is not characterized. In this study, we explored thalamoprefrontal circuit signaling in mice and connectivity dynamics in humans over the course of learning a homologous psychomotor task. In mice, we targeted a genetically encoded Ca2+indicator to the mediodorsal-prefrontal (MdT-dmPFC) projection and used fiber photometry to record synaptic dorsomedial PFC (dmPFC) activity. As learning sessions progressed, all mice demonstrated a decrease in reaction time (RT) performance on successful trials (p<0.001). In concomitant synaptic MdT-dmPFC circuit activity across sessions, we observed a significant increase in activity during the anticipatory (p<0.01) and reward retrieval (p<0.01) periods, and a non-significant trend towards an increase in preparatory activity (p<0.15). However, following the learning period, during task re-exposure, we observed a significant shift in circuit activity, away from anticipatory (p<0.001) and towards the preparatory period (p<0.001) over the course of re-exposure sessions. Furthermore, we observed an emergence of a learner (decrease in RT) and a non-learner group (increase in RT) during the task re-exposure period. Over the course of a single analogous task session in humans, we also observed a learner and a non-learner group. When analyzing the thalamoprefrontal regional connectivity dynamics of early and late trials for learners, we observed a significant increase in low frequency and decrease in high frequency synchrony (connectivity tilt) in thalamoprefrontal pathways during preparatory and anticipatory periods. Interestingly, pairwise interactions specifically between the anterior corona radiata (ACR) and superior frontal gyrus (SFG), the human homolog to the genetically targeted MdT-dmPFC circuitry in mice, in fact demonstrated a robustly opposite connectivity tilt effect distinguishing learners from non-learners (Cohens d > 2). Overall, these findings may provide cross-species evidence of novel, conserved thalamoprefrontal circuit mechanisms of adaptive learning.

neuroscience↗

bioRxiv2025

Electrophysiological Brain Connectivity and Subjective States Evoked by Electrical Stimulation of the Human Mediodorsal Thalamus

Recent advances in human intracranial EEG (iEEG) have enabled new investigations into the role of the thalamus in human brain functions. In this study, we applied direct intracranial electrical stimulation (iES) to the mediodorsal (MD) subregion of the thalamus using both high-frequency (50 Hz, iESHF) and low-frequency (0.5 Hz, iESLF) procedures to examine its impact on conscious experience and causal brain connectivity in 30 patients with focal refractory epilepsy (128 electrode contacts; 4 {+/-} 1 MD sites per patient). iESHF of the MD elicited reportable changes in conscious experience in 11 of 12 patients (39 sites; 83 stimulations across 27 unique pairs) - predominantly in the visceral, emotional, or somatosensory domains and often described as unpleasant without any lateralization effect. Our connectivity analyses based on iESLF revealed that the cingulate and insular cortices produced stronger electrophysiological responses in the MD (inflow connectivity) than did the sites in the prefrontal cortex (PFC) within the same individuals. Moreover, MD stimulation showed its strongest outflow connectivity to the cingulate, insular, and PFC regions, all significantly stronger than to medial temporal lobe (MTL) structures. Notably, inflow from both MTL and insula sites to the MD were significantly stronger than their reverse directions, indicating clear asymmetry in connectivity. These findings provide direct evidence that stimulation of the human thalamus can modulate conscious experience. They also highlight the extensive bidirectional connectivity between the MD and cingulate and insular cortices along with asymmetric connectivity between the MD and MTL and insula sites in the human brain. SIGNIFICANCE STATEMENTOur findings provide a functional and causal map of the mediodorsal thalamus (MD) in the human brain. We provide direct evidence that stimulation of the human thalamus can modulate conscious experience. This study also holds clinical and translational value for identifying thalamic pathways involved in the propagation and generalization of seizures, especially seizures involving the medial temporal lobe, as well as for neuromodulation in epilepsy and other neuropsychiatric disorders, as MD stimulation may not be well-tolerated in human subjects.

neuroscience↗

bioRxiv2024

Causal Cortical and Thalamic Connections in the Human Brain

The brains functional architecture is intricately shaped by causal connections between its cortical and subcortical structures. Here, we studied 27 participants with 4864 electrodes implanted across the anterior, mediodorsal, and pulvinar thalamic regions, and the cortex. Using data from electrical stimulation procedures and a data-driven approach informed by neurophysiological standards, we dissociated three unique spectral patterns generated by the perturbation of a given brain area. Among these, a novel waveform emerged, marked by delayed-onset slow oscillations in both ipsilateral and contralateral cortices following thalamic stimulations, suggesting a mechanism by which a thalamic site can influence bilateral cortical activity. Moreover, cortical stimulations evoked earlier signals in the thalamus than in other connected cortical areas suggesting that the thalamus receives a copy of signals before they are exchanged across the cortex. Our causal connectivity data can be used to inform biologically-inspired computational models of the functional architecture of the brain.

neuroscience↗

bioRxiv2023

Cross regional coordination of neural activity in the human brain during autobiographical self-referential processing

For the human mind to operate, populations of neurons across remote regions of the brain need to coordinate their activity in the subsecond temporal scale. To date, our knowledge of such fast interactions involving cortical and subcortical structures in large brains, such as the human brain, remains limited. Here, we used stereo-electroencephalography (sEEG) recordings across four brain regions that are known, from decades of work, to be important for autobiographical memory processing. Our recordings involved 31 human participants implanted with intracranial electrodes in the hippocampus (HPC), posteromedial cortex (PMC), and ventromedial, as well as orbital subregions of the prefrontal cortex (OFC). In 14 subjects, we also recorded simultaneously in the anterior thalamus (ANT) across various experimental conditions and with direct electrical stimulations. Our observations provide new lines of correlative and causal evidence about the spatiotemporal profile of oscillatory coordination of cortical and subcortical activity during self-referential memory-based processing.

neuroscience↗

bioRxiv2022

Multisite Thalamic Recordings to Characterize Seizure Propagation in the Human Brain

Neuromodulation of the anterior nuclei of the thalamus (ANT) has shown to be efficacious in patients with refractory focal epilepsy, but it is not uniformly effective. One important uncertainty is to what extent thalamic subregions other than the ANT are recruited earlier and more prominently in the propagation of seizures in patients with presumed temporal lobe epilepsy (TLE). To address this unknown, we studied 11 patients with clinical manifestations of TLE planned to undergo invasive stereo-encephalography (sEEG) monitoring. We extended cortical electrodes to reach thalamic nuclear subdivisions in the anterior (ANT), middle (mediodorsal) and or posterior (pulvinar) sites. This multisite thalamic sampling was without any adverse events. Intracranial EEG (iEEG) recordings confirmed seizure-onset in medial temporal lobe, insula, orbitofrontal and temporal neocortical sites - highlighting the importance of iEEG for more accurate localization of seizure foci. Visual review of EEGs documented early and prominent involvement of specific thalamic sites. Seizures originating from the same brain origin produced a stereotyped thalamic EEG signature. Visual review of EEGs, validated with singlepulse corticothalamic evoked potentials, documented early and prominent involvement of thalamic sites that would have not been predicted given the anatomy of seizure onset zones. Pulvinar was involved earlier and more prominently than other sampled nuclear subgroups in 60% of patients, even though all patients had a presumed diagnosis of TLE prior to invasive monitoring. Our findings document the feasibility and safety of multisite sampling from the human thalamus and suggest that the anatomy of thalamic involvement may not be entirely predictable on the basis of clinical information or lobar localization of seizures. Future clinical trials can establish whether offering more personalized targets for thalamic neuromodulation will lead to greater meaningful improvements in outcome.

neuroscience↗

bioRxiv2022

Anticipatory influences on simple sensory-motor behaviors are encoded by rapidly fluctuating neural dynamics across the human brain

Human behavior can be highly sensitive to anticipation, but the mechanisms underlying this sensitivity are poorly understood. We obtained intracranial electrocephalography (iEEG) measurements in neurosurgical patients as they performed a simple sensory-motor task with variable (short or long) foreperiod delays that affected anticipation of the cue to respond. Participants showed two forms of anticipatory response biases, distinguished by more premature false alarms (FAs) or faster response times (RTs) on long-delay trials. These biases had distinct neural signatures in prestimulus neural activity modulations that were distributed and intermixed across the brain: the FA bias was most evident in preparatory motor activity immediately prior to response-cue presentation, whereas the RT bias was most evident in visuospatial activity at the beginning of the foreperiod. These results suggest that human anticipatory behavior emerges from a combination of motor-preparatory and attention-like modulations of neural activity, implemented by anatomically widespread and intermixed, but functionally identifiable, brain networks. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=190 HEIGHT=200 SRC="FIGDIR/small/496029v2_ufig1.gif" ALT="Figure 1"> View larger version (52K): org.highwire.dtl.DTLVardef@1ca47corg.highwire.dtl.DTLVardef@72d43borg.highwire.dtl.DTLVardef@cb875dorg.highwire.dtl.DTLVardef@23f348_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗