Search bioRxiv⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.64898/2026.01.26.700604

Driving theta-gamma oscillations modulates extrasynaptic GABAergic tone: a tACS-TMS study

Lasbareilles, C.·Mancini, V.·Pogosyan, A.·Zhang, H.·Austin, C.·Tan, H.·Stagg, C.
View original source ↗Export metadata ↓

Abstract

BACKGROUNDTheta-gamma phase-amplitude coupled ({theta}{gamma}-PAC) oscillations in primary motor cortex (M1) have been shown to support motor skill acquisition. Past research has shown that driving gamma activity at the theta peak (TGP), but not the theta trough (TGT) using transcranial alternating current stimulation (tACS) enhances motor learning (Akkad et al., 2021). However, the neurophysiological mechanisms underlying this phase-specific effect remain unclear. METHODSIn a double-blind, sham-controlled, cross-over study, twenty-two healthy participants received 20 minutes of 75Hz/6Hz TGP-tACS, TGT-tACS, or sham stimulation over M1. We used paired-pulse transcranial magnetic stimulation (TMS) to assess GABAergic and NMDAR-mediated activity before, during, and after tACS. Outcome measures included short-interval intracortical inhibition at 1ms (SICI1ms; extrasynaptic GABAergic tone) and 2.5ms (SICI2.5ms; synaptic GABAA activity), intracortical facilitation at 12ms (ICF12ms; NMDAR activity), and motor evoked potential (MEP) amplitude (corticospinal excitability). RESULTSTGP-tACS selectively decreased SICI1ms, a putative marker of extrasynaptic GABAergic tone (main effect of Stimulation: p=.021), with significant differences between TGP and TGT during late stimulation (p=.047). No significant effects were observed on corticospinal excitability, synaptic GABAergic activity (SICI2.5ms), or NMDAR signalling (ICF12ms). CONCLUSIONSDriving theta-gamma oscillations at the theta peak using tACS specifically modulates extrasynaptic GABAergic tone in M1 without affecting corticospinal excitability or synaptic inhibition. Given that reductions in GABAergic signalling supports motor learning, these findings provide a neurophysiological mechanism for the phase-specific behavioural effects of {theta}{gamma}-PAC tACS and suggest a potential therapeutic approach for facilitating motor recovery after stroke. HighlightsO_LITheta-gamma peak tACS selectively reduces extrasynaptic GABA in human motor cortex C_LIO_LIOnly gamma at the peak, not trough, of theta stimulation modulates GABA C_LIO_LINo effects on corticospinal excitability, synaptic GABA, or NMDAR signalling C_LIO_LItACS-TMS reveals mechanism for phase-dependent motor learning effects C_LI

Explore related subjects

neurosciencePreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Lasbareilles, C., Mancini, V., Pogosyan, A., Zhang, H., Austin, C., Tan, H., Stagg, C.. 2026-01-27. Driving theta-gamma oscillations modulates extrasynaptic GABAergic tone: a tACS-TMS study. https://doi.org/10.64898/2026.01.26.700604

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

The Unreasonable Effectiveness of Cell Types in Describing Neuronal Physiological Features

Single-cell RNA sequencing (scRNA-seq) captures detailed gene expression profiles at scale, while patch-clamp recordings measure intrinsic neuronal electrophysiological properties. Modeling the relations between these two modalities remains a challenge. Here, we compare how well electrophysiological features can be predicted by traditional transcriptomic cell type classification, representations derived from a foundational model (scGPT) pretrained on large-scale scRNA-seq datasets, ion channel-coding genes, and highly variable genes. Using paired transcriptomic and electrophysiological patch-sequencing data from 495 human neurons from neurosurgical tissue, we find that cluster-level cell type representations consistently outperform highly variable gene selection, ion channel gene selection, and context-enriched scGPT embeddings. Notably, performance varies across model architectures and initializations, and the best results are obtained by combining the outputs of separate cell type and scGPT-based models. Together, these findings suggest that traditional discrete cellular classification is highly effective in predicting physiological features. For maximum performance it can be complemented by pretrained transformer models.

neuroscience↗
bioRxiv2026

A nonlinear inhibition pathway underlying cortical responses to tuned holographic optogenetic perturbations

Optogenetics enables causal manipulation of cortical activity. Perturbation responses can be counterintuitive due to network interactions, making theory essential for predicting them. Existing approaches often rely on linear approximations, which fail for many biologically relevant perturbations. Here we develop a nonlinear theory of responses to holographic perturbations in cell-type-specific recurrent networks with structured connectivity. We fit a nonlinear model to mouse V1 data, which shows cotuned-ensemble suppression: perturbing spatially clustered neurons with similar preferred orientations yields markedly stronger short-range suppression than perturbing untuned ensembles. We show that cotuned-ensemble suppression arises from a feature-tuned, nonlinear inhibition pathway implicating somatostatin-positive (SST) interneurons. The theory predicts that cotuned ensembles suppress parvalbumin-positive (PV) neurons but facilitate SST neurons, and links the degree of cotuned-ensemble suppression or facilitation to the variance of the SST response. This framework identifies mechanisms by which nonlinear inhibition sculpts cortical dynamics and establishes a predictive basis for targeted optogenetic interventions.

neuroscience↗
bioRxiv2026

Proteomic signatures of APOE ε4 across human tissues and cell types in Alzheimers disease

The apolipoprotein E {varepsilon}4 (APOE {varepsilon}4) allele is the strongest genetic risk factor for late-onset Alzheimers disease (AD). However, the underlying molecular mechanisms remain unclear. This study included 1691 participants from the Religious Orders Study and Rush Memory and Aging Project (ROSMAP), 1226 participants from the Accelerating Medicines Partnership - Alzheimers Disease (AMP-AD) Diverse Cohorts Study, and 735 participants from the Alzheimers Disease Neuroimaging Initiative (ADNI). To characterise APOE {varepsilon}4 molecular effects, we analysed proteomic data from plasma, cerebrospinal fluid (CSF), and induced pluripotent stem cell (iPSC)-derived astrocytes and neurons, as well as transcriptomic and proteomic data from multiple brain regions. The association of APOE {varepsilon}4 with AD neuropathology was also examined. APOE {varepsilon}4 carriers shared a plasma proteomic signature enriched for immune processes, irrespective of AD diagnosis. A machine learning classifier trained on this signature discriminated APOE {varepsilon}4 carriers from non-carriers in an independent cohort using CSF proteomics. APOE {varepsilon}4 carriage was associated with higher Braak stages and Consortium to Establish a Registry for Alzheimers Disease (CERAD) score. However, only limited APOE {varepsilon}4-associated transcriptomic and proteomic changes were observed in bulk brain tissue, with poor cross-layer concordance. Proteomic analyses of iPSC-derived astrocytes and neurons further revealed cell-type-specific APOE {varepsilon}4-associated changes. APOE {varepsilon}4 is associated with a consistent proteomic signature across plasma and CSF. Its molecular effects in the brain differ across cell types, brain regions and molecular layers. These findings support the need for cell-type-resolved multi-omic studies to elucidate how APOE {varepsilon}4 confers AD risk.

neuroscience↗