Biology subjects

Stagg, C. J.

Publications and source records attributed to Stagg, C. J..

At least 19 recordsLinked to original sources

bioRxiv2026

Longitudinal neurochemical profiling after experimental stroke using edited MR spectroscopy

Background: Alterations in excitatory and inhibitory neurotransmission contribute to stroke pathology and recovery, yet longitudinal assessment of these changes in vivo remains limited. We investigated the feasibility of longitudinal edited proton magnetic resonance spectroscopy (1H-MRS) to quantify {gamma}-aminobutyric acid (GABA) and glutamate following experimental focal cerebral ischaemia. Methods: Male rats underwent endothelin-1-induced striatal ischaemia or sham surgery. Longitudinal edited 1H-MRS was performed at baseline and 2-, 7- and 30-days post-stroke at 7-tesla with a MEGA-sLASER sequence. A voxel was positioned within the ipsilesional motor cortex adjacent to the lesion. Behavioural outcomes (grip strength, adhesive removal and CatWalk gait analysis) were assessed alongside spectroscopy, and immunohistochemistry for Iba1, GFAP and ICAM-1 was performed at 30 days. Results: Stroke induced a transient reduction in GABA+/tCr within the ipsilesional motor cortex, with significantly lower concentrations than sham animals at 7 days (p<0.05), returning to baseline by 30 days. Glutamate/tCr and GABA/glutamate ratio were unchanged throughout the study. Behavioural deficits were mild, with significant effects on motor outcomes such as grip strength, gait swing speed and paw placement, while sensory areas of the brain seemed largely unaffected. Histological analysis revealed no persistent differences in cortical Iba1, GFAP or ICAM-1 immunoreactivity at 30 days. Conclusions: Longitudinal 1H-MRS is a feasible approach for monitoring dynamic changes in inhibitory neurochemistry following experimental stroke. The transient reduction in peri-lesional GABA, despite minimal behavioural impairment and an absence of persistent cortical inflammation, supports the use of edited spectroscopy as a translational tool to investigate neurochemical mechanisms underlying network dynamics in post-stroke recovery.

neuroscience↗

bioRxiv2026

Effects of cholinergic potentiation on resting-state functional connectivity in healthy adults

Acetylcholine is a key attentional neuromodulator, yet its effects on large-scale organisation of resting-state networks remain poorly understood. Here, we investigated whether acute cholinergic potentiation with the acetylcholinesterase inhibitor donepezil modulates functional connectivity within and between resting-state networks involved in attention. Nineteen healthy young adults completed a double-blind, placebo-controlled crossover study using 7T resting-state functional MRI (rs-fMRI), with imaging performed before and after administration of donepezil or placebo. We tested whether donepezil altered functional connectivity within and between the dorsal attention, ventral attention, default mode, and frontoparietal networks and whether it improved attentional orienting in the same volunteers. Voxel-wise analysis revealed a significant donepezil-related increase in dorsal attention network connectivity within the left inferior parietal cortex. We did not observe donepezil-related changes within the ventral attention, default mode, or frontoparietal networks. Network-level analyses did not identify significant global changes in network strength. Exploratory analyses indicated reduced coupling between the dorsal attention and default mode networks following donepezil relative to placebo, although this result did not survive correction for multiple comparisons. Donepezil did not significantly improve attentional orienting at the group level. However, exploratory analyses suggested that greater donepezil-related enhancement of functional connectivity within the identified left inferior parietal cluster was associated with greater improvement in attentional orienting. These findings suggest that acute cholinergic potentiation does not globally enhance resting-state connectivity across attentional networks in healthy young adults. Instead, donepezil may selectively modulate localised dorsal attention network circuitry, particularly within left inferior parietal cortex, a region implicated in sensory integration and externally oriented cognition.

neuroscience↗

bioRxiv2026

Distinct In Vivo Electrophysiological Profiles of Mediodorsal Thalamus Subdivisions

The mediodorsal nucleus of the thalamus (MD) plays a key role in complex cognitive processes, and its dysfunction is linked to various neurological and psychiatric conditions. The MD is divided into three parts that vary in anatomical connectivity, molecular expression, and ex vivo electrophysiology. Here, we describe in vivo single-neuron electrophysiological recordings across the three MD subdivisions in head-fixed, behaving, adult, wildtype mice. We report large differences in extracellular waveforms, spiking activity, and burst firing characteristics across MD subdivisions. Specifically, central MD subdivision (MDc) neurons showed markedly increased waveform amplitude, higher spontaneous firing rate, and increased burst firing compared to medial (MDm) and lateral (MDl) subdivision neurons. Single-neuron electrophysiology features were sufficient to classify neurons into respective anatomical subdivisions. Hierarchical clustering revealed MDc is distinct from MDl and MDm and more akin to other, non-MD thalamic nuclei. Together, these data suggest distinct in vivo electrophysiological profiles of MD subdivisions, posing implications for investigating MD thalamus in health and disease.

neuroscience↗

bioRxiv2026

A hippocampal neuroimaging signature of neurovascular insulin signalling links metabolism to mood

Depression is a leading cause of global disability and is increasingly linked to systemic metabolic dysfunctions, including insulin resistance. However, the biological pathways connecting metabolic state to affective symptoms are unresolved. A growing body of evidence indicates that insulin, beyond its role in systemic glucose homeostasis, supports brain metabolism, synaptic function and cognition, yet its contribution to mood regulation remains unclear. Here, we identify a human hippocampal metabolic signature associated with glycaemic variation in individuals with depression. Using multimodal neuroimaging, we show that hippocampal concentrations of GABA and lactate correlate with HbA1c and with mood severity, while functional connectivity between the hippocampus and the default mode network tracks affective symptoms independently of adiposity. To causally probe these relationships, we generated a mouse model of hippocampus-specific insulin receptor depletion. Unexpectedly, reducing insulin signalling at the blood brain barrier enhanced neuronal metabolism and attenuated anxiety-like behaviour. Notably, hippocampal lactate and GABA levels similarly tracked anxiety-related behaviour in mice, mirroring their association with symptom severity in humans. Together, these findings identify a conserved neurometabolic signature linking hippocampal insulin signalling to affective state, and reveal that brain insulin resistance exerts context- and cell-type-specific effects on behaviour. This work establishes a mechanistic basis for brain insulin resistance in depression and highlights the hippocampus as a critical hub for metabolic modulation of mood.

neuroscience↗

bioRxiv2026

Non-invasive measurement of neurotransmitter-specific glucose metabolism in the human brain using proton-observed proton-edited 13C-MRS (POPE13C-MRS)

Non-invasive measurement of neurotransmitter-specific glucose metabolism in the human brain remains a major challenge, limiting mechanistic insight into excitatory-inhibitory imbalance across neurological and psychiatric disorders. Existing approaches either lack neurotransmitter specificity or require specialised hardware that constrains clinical applicability. Here, we introduce proton-observed proton-edited 13C magnetic resonance spectroscopy (POPE13C-MRS), an approach that enables non-invasive detection of glutamate, GABA, and lactate metabolism using standard proton MRI hardware. The method combines administration of 13C-labelled glucose with targeted proton editing to detect 1H-13C satellite resonances. Using a cross-species proof-of-concept approach, we demonstrate consistent detection of neurotransmitter-specific 13C labelling in mice and feasibility in the human brain at ultra-high field. POPE13C-MRS provides a readout of glutamatergic and GABAergic metabolism, enabling in vivo assessment of excitatory-inhibitory metabolic balance. This establishes a means for probing neurometabolic coupling with potential applications in translational and clinical neuroscience.

neuroscience↗

bioRxiv2026

Higher-Order Thalamus is Pivotal in Schizophrenia-Associated Pathophysiology

Synaptic dysfunction has been proposed as cellular pathophysiology underlying schizophrenia, yet the brain-wide distribution of dysfunctional circuits at single-neuron resolution has remained unknown. Here, we perform comprehensive multi-probe electrophysiological investigations in vivo in the Grin2a+/- preclinical model for schizophrenia and control animals, recording across [~]45 brain regions spanning cortex, striatum, hippocampus, and thalamus. Mutants displayed distributed and graded alterations across regions, with prominent activity reductions in higher-order thalamus and cross-parameter alterations across prefrontal cortices, striatum, and hippocampus. Restoration of higher-order thalamic activity in mutants was sufficient to normalize alterations in connected prefrontal cortices and striatum and unexpectedly cascaded to hippocampus and sensory cortices. Thus, higher-order thalamus plays a pivotal role in schizophrenia pathophysiology and restoration of a single informed locus could present a potent therapeutic strategy.

neuroscience↗

bioRxiv2025

Closed-loop beta stimulation enhances beta activity and motor behaviour

Movement-related beta event-related synchronization (ERS) has been linked to motor control and learning, showing potential as a therapeutic target for those with movement deficits, such as stroke survivors. However, whether directly modulating beta ERS can causally influence motor performance remains unclear, largely due to the lack of methods designed to specifically target this neural activity. To address this gap, we developed a novel behaviourally-driven, closed-loop transcranial alternating current stimulation (tACS) approach to target movement-related beta ERS during a visuomotor adaptation task. We found that the behaviourally-driven, closed-loop beta-tACS specifically enhances beta ERS without affecting beta event-related desynchronization (ERD). Critically, this targeted enhancement significantly improves retention of motor adaptation. These findings establish a causal relationship between beta ERS and motor behaviour and highlight the potential of behaviourally-driven beta-tACS as a therapeutic approach for improving motor function in clinical populations characterized by impaired beta activity.

neuroscience↗

bioRxiv2025

Modulation of motor cortical theta and gamma oscillations using phase-targeted, closed-loop optogenetic stimulation of local excitatory and inhibitory neurons

Theta and gamma oscillations are prominent features of cortical local field potentials (LFPs) and stimulation of the motor cortex at these frequencies can enhance motor learning. Phase-targeted closed-loop stimulation could provide a more precise and effective method to modulate these oscillations, particularly if stimulation parameters could harness the dynamics of the specific circuit mechanisms underpinning the generation of these activities. To address this question, we defined the response of theta-and gamma-frequency oscillations in the motor cortex to closed-loop optogenetic stimulation of excitatory pyramidal neurons and inhibitory interneurons transfected with Channelrhodopsin-2 in awake, head-fixed RBP4-Cre (retinol-binding-protein-4) and PV-Cre (parvalbumin) mice, respectively. Phase-targeted blue-light pulses were delivered using the OscillTrack algorithm to track theta phase in the cortical LFP in real time and trigger stimulation at one of four target theta phases. Stimulation was delivered over a quarter of the target theta cycle, either as a single continuous pulse ("continuous" protocol) or three short pulses at gamma (75Hz) frequency ("gamma" protocol). Stimulation of both neuron types, using either stimulation protocol, modulated theta power in a phase-dependent manner, with continuous stimulation of excitatory cells leading to stronger modulation. Phase-dependent amplification during stimulation of excitatory vs inhibitory neurons was offset by 90{degrees}, in line with predictions from computational models. Open-loop replay of previously recorded closed-loop stimulation patterns did not elicit the same phase-specific effects, demonstrating the necessity of the closed-loop interaction to produce these effects. Stimulation of pyramidal neurons using the gamma protocol amplified gamma power, independently of target theta phase. These findings reveal phase-dependent amplification of cortical theta power can be induced by stimulation of local excitatory or inhibitory neurons, with a phase-offset likely resulting from circuit interactions. This approach can be used to inform the development of brain stimulation methods to modulate these activities more effectively in humans.

neuroscience↗

bioRxiv2025

Dual-site beta transcranial alternating current stimulation during a bimanual coordination task modulates functional connectivity between motor areas

BackgroundCommunication within brain networks depends on functional connectivity. One promising approach to modulate such connectivity between cortical areas is dual-site transcranial alternating current stimulation (tACS), which non-invasively applies weak alternating currents to two brain areas. Objectives/HypothesesIn the current study, we aimed to modulate inter-regional functional connectivity with dual-site tACS to bilateral primary motor cortices (M1s) during bimanual coordination and, in turn, alter behaviour. MethodsUsing functional magnetic resonance imaging (fMRI), we recorded participants brain responses during a bimanual coordination task in a concurrent tACS-fMRI design. While performing a slow and fast version of the task, participants received one of three types of beta (20 Hz) dual-site tACS over both M1s: in-phase, jittered-phase or sham, in a within-subject, repeated measures design. ResultsWhile we did not observe any significant tACS effects on behaviour, the study revealed a disruptive effect of in-phase tACS on interhemispheric connectivity. Additionally, the two active types of tACS (in-phase and jittered-phase) differed in the task-related M1 connectivity with other motor cortical regions, such as premotor cortex and supplementary motor area. Furthermore, individual E-field strengths were related to functional connectivity in the in-phase condition. ConclusionsDual-site beta tACS over both M1s altered functional connectivity between motor areas. However, this effect did not translate to the behavioural level, possibly due to compensatory mechanisms. HighlightsO_LIInterhemispheric connectivity between the primary motor cortices was targeted with dual-site beta tACS during bimanual coordination. C_LIO_LIIn-phase as compared to sham tACS disrupted interhemispheric connectivity during task performance. C_LIO_LIIn-phase and jittered-phase tACS led to different task-related functional connectivity patterns within the motor network. C_LIO_LIThe relationship between individual in-phase E-field strengths and interhemispheric connectivity depended on task demand. C_LIO_LIThere were no significant tACS effects on behavioural performance of bimanual coordination, possibly due to compensatory mechanisms. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=143 SRC="FIGDIR/small/647211v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@17ecdd8org.highwire.dtl.DTLVardef@1fc5b25org.highwire.dtl.DTLVardef@c3df42org.highwire.dtl.DTLVardef@17671bb_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2025

Baclofen, a GABAB receptor agonist, impairs motor learning in healthy people and changes inhibitory dynamics in motor areas

Inhibition mediated by {gamma}-aminobutyric acid (GABA) is implicated in motor plasticity and learning, with [GABA] in the motor cortex decreasing during motor learning. However, the causal relationship between [GABA] and learning has yet to be determined. Here, we conducted a within-subject, double-blind, placebo-controlled, crossover study to investigate the effect of increased GABAergic inhibition via GABAB-receptor agonist baclofen on motor learning and Magnetic Resonance Spectroscopic Imaging (MRSI) metrics. Increasing GABA-mediated inhibition with baclofen did not change response times, but significantly impaired motor sequence learning. In parallel, we demonstrated a blunting of the expected decrease in [GABA] during motor learning. These results highlight a causal role for GABAergic inhibition in motor learning and may have clinical implications: baclofen is commonly used to treat post brain-injury spasticity, but may impair motor learning during rehabilitation.

neuroscience↗

bioRxiv2024

Default mode and motor networks facilitate early learning of implicit motor sequences: a multimodal MR spectroscopy and fMRI study

Learning new motor skills is a fundamental process that involves the sequencing of actions. Skill develops with practice and time, and manifests as performance that is fast and accurate. Although we know that learning can occur through an implicit process in the absence of conscious awareness, and across multiple temporal scales, the precise neural mechanisms mediating implicit motor sequence learning remain poorly understood. Similarly, the capacity for interventions with known influence on learning and memory, such as cardiovascular exercise, to facilitate implicit learning is yet to be clearly established. Here, we investigated the neuroplasticity of implicit motor sequence learning and the effect of acute exercise priming. Healthy adults (39.5% female) aged 22.55 {+/-} 2.69 years were allocated to either a high-intensity exercise (HIIT) group (n = 16) or to a very low-intensity control group (n = 17). Following exercise, participants performed a serial reaction time task. MR spectroscopy estimates of sensorimotor gamma-aminobutyric acid (GABA) were acquired before and after exercise, and during task performance, and resting-state fMRI was acquired at the end of the protocol. We show that early stages of learning are linked to default mode network connectivity, while the overall degree of learning following sustained practice is associated with motor network connectivity. Sensorimotor GABA concentration was linked to the early stages of learning, and GABA concentration was modulated following HIIT, although the two were not related. Overall, via integration of multiple neuroimaging modalities we demonstrate that interactions between hippocampal and motor networks underlie implicit motor sequence learning. Key points summary- Motor learning occurs across different temporal scales and can arise implicitly in the absence of conscious awareness. - Explicit motor learning is linked to the brains primary inhibitory neurotransmitter, GABA, and interactions across motor and hippocampal networks. - Whether these same neural mechanisms are implicated in implicit learning is unclear. Similarly, the capacity to influence learning via priming with cardiovascular exercise is yet to be clearly established. - We show that early implicit learning is underpinned by default mode network connectivity and sensorimotor GABA concentration, while total learning following sustained practice is linked to motor network connectivity. We also found that HIIT exercise elevated sensorimotor GABA concentration, but not the magnitude of implicit learning. - Overall, our results highlight shared involvement of default mode and motor networks in implicit motor sequence learning.

neuroscience↗

bioRxiv2024

The effects of varying intensities of unilateral handgrip fatigue on bilateral movement

The human ability to maintain adequate movement quality despite muscle fatigue is of critical importance to master physically demanding activities of daily life and for retaining independence following motor impairments. Many real-life situations call for asymmetrical activation of extremity muscles leading to unilateral manifestations of muscle fatigue. Repeated unilateral handgrip contractions at submaximal force have been shown to be associated with neural dynamics in both contralateral and ipsilateral cortical motor areas and improved response times of the contralateral, unfatigued homologue in a button-press task. However, it remains unclear whether the observed improvement in contralateral response latency translates into higher-level benefits in movement quality. To investigate this, 30 healthy participants underwent unilateral handgrip fatiguing tasks at 5%, 50%, and 75% of maximum voluntary contraction (MVC) force. Subsequently, bimanual movement quality was assessed in an object-hit task using a Kinarm robot. The protocol at 50% and 75% of MVC elicited clear signs of muscle fatigue compared to the control condition (5%) measured by a decline in force, post-exercise deterioration in MVC, characteristic changes in surface electromyography magnitudes, and increases in ratings of perceived exertion. No change was observed on kinematic measures in the object-hit task for both arms indicating that unilateral handgrip fatigue did not elicit measurable effects on higher-level movement quality on the ipsilateral or contralateral homologue. Previously reported improvements on contralateral response latency were not found to translate into advanced movement quality benefits.

neuroscience↗

bioRxiv2024

Differential beta and gamma activity modulation during unimanual and bimanual motor learning

Movement-related dynamics in the beta and gamma bands have been studied in relation to motor execution and learning during unimanual movements, but their roles in complex bimanual tasks remain largely unexplored. This study aimed to investigate how beta and gamma activity differs between unimanual and bimanual movements, and how these neural signatures evolve during the learning process. Our motor task incorporated varying levels of bimanual interaction: unimanual, bimanual-equal, and bimanual-unequal. Magnetoencephalography data were recorded during task performance, and beta and gamma dynamics were quantified. As expected, increasing task complexity from unimanual to bimanual-equal, and then to bimanual-unequal movements resulted in slower and less accurate performance. Across all conditions, significant beta event-related desynchronization (ERD) and gamma event-related synchronization (ERS) were observed during movement, as well as beta ERS after movement. Bimanual movements exhibited greater beta ERD, beta ERS, and gamma ERS compared to unimanual movements. With practice, participants demonstrated faster and more accurate movements, accompanied by enhanced beta ERS responses. Furthermore, learning-related reductions in errors correlated with increases in beta ERS. These findings suggest the distinct behavioural and neural demands of unimanual versus bimanual movements and highlight the important role of beta dynamics in motor performance and learning.

physiology↗

bioRxiv2024

Brain-wide population activity during reaching integrates action-mediated goal expectation

Anticipating the outcomes of actions is central to goal-directed behaviour, but how such expectations are encoded across the brain during ongoing movement remains unclear. To address this, we recorded spiking activity from cortical and subcortical regions using multiple Neuropixels probes simultaneously in head-fixed mice performing a water-reaching task. We found that distributed neural population dynamics were strongly modulated by the availability of reward beyond their encoding of forelimb kinematics. Principal component analysis revealed conserved population dynamics across brain regions and sessions that depended on reach amplitude and reward availability. Generalized linear models revealed outcome-related encoding within region-specific population dynamics, in addition to kinematic encoding, with the strongest outcome signals expressed in frontal cortico-thalamic regions. Unsupervised cluster analysis further identified outcome-encoding subpopulations that were enriched in frontal cortices and disproportionally contributed to the shared global latent dynamics. Together, these findings demonstrate that action-mediated outcome expectations are encoded in movement-related population dynamics that are shaped by functional clusters of neurons across the brain.

neuroscience↗

bioRxiv2024

7 Tesla MRS estimates of GABA concentration relate to physiological measures of tonic inhibition in the human motor cortex

GABAergic neurotransmission within the cortex plays a key role in learning and is altered in several brain diseases. Quantification of bulk GABA in the human brain is typically obtained by Magnetic Resonance Spectroscopy (MRS). However, the interpretation of MRS-GABA is still debated. A recent mathematical simulation contends that MRS detects extrasynaptic GABA, mediating tonic inhibition. Nevertheless, no empirical data have yet confirmed this hypothesis. Here we collected ultra-high field 7 Tesla MRS and Transcranial Magnetic Stimulation coupled with high-density Electroencephalography (TMS-hdEEG) from the motor cortex of twenty healthy participants (age 23.95{+/-}6.4), while they were at rest. We first applied a Neural Mass Model to TMS-evoked potentials to disentangle the contribution of different GABAergic pools. We then assessed to which of these different pools MRS-GABA was related to by means of Parametric Empirical Bayesian (PEB) analysis. We found that MRS-GABA was mostly positively related to the NMM-derived measures of tonic inhibition and overall functionality of the GABAergic synapse. This relationship was reliable enough to predict MRS-GABA from NMM-GABA. These findings clarify the mesoscopic underpinnings of GABA levels measured by MRS and will contribute to the concretization of MRS-GABA promises to improve our understanding of human behaviour, brain physiology and pathophysiology. Key pointsO_LIGABA neurotransmission is essential for synaptic plasticity and learning (especially motor learning) and is altered in several brain disorders, such as epilepsy and stroke. C_LIO_LIQuantification of GABA in the human brain is typically obtained by Magnetic Resonance Spectroscopy (MRS). However, the interpretation of MRS-GABA is still debated. C_LIO_LIBy using a biophysical Neural Mass Model, here we show that MRS-GABA relates to physiological measures of tonic inhibition in the human cortex. C_LI

neuroscience↗

bioRxiv2024

Ultrasound system for precise neuromodulation of human deep brain circuits

Transcranial ultrasound stimulation (TUS) has emerged as a promising technique for non-invasive neuromodulation, but current systems lack the precision to target deep brain structures effectively. Here, we introduce an advanced TUS system that achieves unprecedented precision in deep brain neuromodulation. The system features a 256-element, helmet-shaped transducer array operating at 555 kHz, coupled with a stereotactic positioning system, individualised treatment planning, and real-time monitoring using functional MRI. In a series of experiments, we demonstrate the systems ability to selectively modulate the activity of the lateral geniculate nucleus (LGN) and its functionally connected regions in the visual cortex. Participants exhibited significantly increased visual cortex activity during concurrent TUS and visual stimulation, with high reproducibility across individuals. Moreover, a theta-burst TUS protocol induced robust neuromodulatory effects, with decreased visual cortex activity observed for at least 40 minutes post-stimulation. These neuromodulatory effects were specific to the targeted LGN, as confirmed by control experiments. Our findings highlight the potential of this advanced TUS system to non-invasively modulate deep brain circuits with high precision and specificity, offering new avenues for studying brain function and developing targeted therapies for neurological and psychiatric disorders. The unprecedented spatial resolution and prolonged neuromodulatory effects demonstrate the transformative potential of this technology for both research and clinical applications, paving the way for a new era of non-invasive deep brain neuromodulation.

neuroscience↗

bioRxiv2023

Tuning the brakes: Modulatory role of transcranial random noise stimulation on inhibition

BackgroundEveryday decision-making requires the ability to flexibly modify and sometimes terminate our actions, such as avoiding a tempting slice of cake to hitting the brakes in an emergency. Neural oscillations, such as beta-band rhythms observed over the medial prefrontal cortex(mPFC), help regulate these context-dependent behaviours. However, how random noise stimulation would modulate neural rhythms and corresponding inhibitory behaviors remain understudied. ObjectivesTo target the mPFC using random noise stimulation and modulate neural activity underlying inhibitory behaviours. MethodsUsing a single-blinded within-subject design, fifteen participants received random noise or sham stimulation in a pseudo-randomized order while performing a Go/Conflict/No-Go task. We measured neural activity and behavior before and after stimulation. ResultsWe show that random noise stimulation significantly improved inhibitory behaviors (4.6{+/-}4.42percent) by reducing the number of errors in No-Go trials. This improvement was a function of participants impulsivity-levels and baseline performance, i.e., impulsive individuals who made more baseline errors improved more after receiving stimulation. At the neural level, we show that random noise stimulation increases low-beta power at stimulation site, mediated by an increase in the duration of intermittent beta-bursts. ConclusionWe show for the first time that random noise stimulation improves the ability to withhold response to unexpected inhibitory cues as a function of an individuals impulsivity level. This improvement could be attributed to increased low-beta band power and intermittent-burst duration. These results suggest that random noise stimulation of the mPFC could potentially be used as a neuromodulatory intervention to target maladaptive behaviors in impulse control disorders.

neuroscience↗

bioRxiv2023

Cortical high gamma power relates to movement speed and is disproportionately reduced after stroke

Motor cortical high-gamma oscillations (60 to 90 Hz) occur at the onset of movement and are spatially focused over the contralateral primary motor cortex. Although high-gamma oscillations are widely recognized for their significance in human motor control, their precise function on a cortical level remains elusive. Importantly, their relevance in human stroke pathophysiology is unknown. Understanding the neurophysiological processes of motor coding could be an important step in improving motor recovery after stroke. We recorded magnetoencephalography data during a thumb movement speed task in 14 chronic stroke survivors, 15 age-matched control participants and 29 healthy young participants. Motor cortical high-gamma oscillations showed a strong relation with movement speed as trials with higher movement speed were associated with greater high-gamma power. Stroke survivors showed reduced cortical high-gamma power, surpassing the effect attributable to decreased movement speed in these participants. Even though motor skill acquisition was evident in all groups, it was not linked to high-gamma power. Our study is, to our knowledge, the first to quantify high-gamma oscillations after stroke, revealing a reduction in movement-related high-gamma power. Moreover, we provide strong evidence for a pivotal role of motor cortical high-gamma oscillations in encoding movement speed.

neuroscience↗