Biology subjects

Güth, M. R.

Publications and source records attributed to Güth, M. R..

5 recordsLinked to original sources

bioRxiv2026

Precision phase targeting of event-related oscillations using real-time closed-loop TMS-EEG

ObjectiveCurrent closed-loop TMS-EEG systems rely on phase prediction algorithms that require highly periodic signals, limiting their ability to target brief, event-related activity. We developed a real-time closed-loop (RT-CL) TMS-EEG system that directly detects oscillatory phase without prediction, enabling phase-locked stimulation within microseconds. MethodsWe validated the system against a prediction-based approach using simulated sine waves and human EEG data (N=18), without active TMS delivery. ResultsAcross frequency-modulated sweeps and spontaneous occipital alpha oscillations (eyes-open vs. closed), the RT-CL system achieved higher triggering probability (11-24%) and reduced the phase error variability (2-10{degrees}). Importantly, when targeting event-related theta oscillations during two spatial navigation tasks, RT-CL produced [~]20% higher triggering probabilities and [~]17{degrees} lower phase error variability than phase prediction. ConclusionThese findings validate the RT-CL system for probing phase-dependent mechanisms during active cognition and pathological brain states. SignificanceBy precisely targeting brief, variable neural signals, RT-CL could be used for the development of personalized TMS interventions for neuropsychiatric disorders during symptom provocation.

neuroscience↗

bioRxiv2026

Right posterior theta facilitates memory encoding and recall during virtual navigation

Despite decades of animal and human intracranial work highlighting the critical role theta oscillations (4-12 Hz) play in memory encoding and recall stage during navigation, the link between scalp recorded human theta oscillations and spatial encoding and recall is lacking. In the present study, we used right posterior theta (RPT) - a scalp-level theta signal believed to be generated in the medial temporal cortex - to examine spatial encoding and recall during virtual spatial navigation. In particular, we recorded EEG from 27 healthy subjects performing a novel virtual Linear Track Memory (LTM) task. During the encoding stage of the task, a reward cue was presented at one of five pillar locations along a linear track. During the recall stage, subjects were presented with images of the five pillars and five new pillars, and were asked to press a button when the rewarded target pillar location appeared. If correct, subjects received 5 cents for that trial. Memory performance was assessed using reaction time, d-prime (d), and response bias ({beta}), and RPT was measured following the onset of the reward cue at bilateral scalp electrodes P7 and P8. Consistent with previous work, RPT peaked approximately 170-300 ms over the right hemisphere (P8) after cue onset, which was significantly increased for reward cues during the encoding stage and for the target pillar during the recall stage. Importantly, general linear model regressions revealed that peak RPT power during the encoding stage significantly predicted higher d and {beta} scores during recall, supporting the relationship between RPT peak power and memory performance. Together, these findings support the proposal that RPT activity reflects the encoding of salient information for the purpose of spatial navigation and a promising candidate biomarker for memory-related functioning in health and disease (e.g., Alzheimers disease).

neuroscience↗

bioRxiv2026

Dose-dependent power and connectivity modulation of low frequency oscillations through transcranial magnetic stimulation in non-human primates.

Transcranial magnetic stimulation (TMS) is a powerful non-invasive tool for safely modulating neural activity in humans. In particular, the left dorsolateral prefrontal cortex (DLPFC) is a common target site for clinical interventions in disorders such as treatment-resistant depression. Yet, clinical trials investigating the efficacy of TMS often lack neural markers of target engagement of the DLPFC. Local field potentials (LFPs), such as prefrontal theta oscillations, have been implicated in the clinical symptoms of these disorders. However, non-invasive electroencephalography (EEG) recordings in humans are limited by their spatial resolution and challenges of interpreting EEG signals. In this study, we investigate the effects of single-pulse TMS applied to the left prefrontal cortex in non-human primates on LFPs recorded through intracranial EEG. Compared to sham TMS, the intensity of active TMS pulses scaled with LFP power changes in a 1-13 Hz range at contacts close to the stimulation site in the prefrontal cortex (e.g., caudate nucleus, anterior cingulate cortex, insular cortex) as well as contacts that were more distal (e.g., posterior cingulate cortex, temporal lobe). To test how TMS modulates connectivity between these regions, we conducted a phase-based connectivity analysis. TMS pulses initially enhanced and then disrupted connectivity at 1-13 Hz between the stimulation site and other contacts. Connectivity rebounded approximately 1500 ms post-stimulation. Only the initial enhancement in connectivity scaled with TMS intensity. Our results demonstrate a dose-dependent power modulation of low frequency LFPs across prefrontal, parietal and temporal cortical regions by single pulses. Furthermore, they show that TMS applied over the left prefrontal cortex can enhance and interrupt short- and long-range connectivity. Our study advances the understanding of the effects of TMS on brain oscillations and connectivity with direct relevance for clinical applications in neuromodulation therapies.

neuroscience↗

bioRxiv2024

Right posterior theta reflects human parahippocampal phase resetting by salient cues during goal-directed navigation

Animal and computational work indicate that phase resetting of theta oscillations (4-12 Hz) in the parahippocampal gyrus (PHG) by salient events (e.g., reward, landmarks) facilitates the encoding of goal-oriented information during navigation. Although well-studied in animals, this mechanism has not been empirically substantiated in humans. In the present article, we present data from two studies (Study 1: asynchronous EEG-MEG | Study 2: simultaneous EEG-fMRI) to investigate theta phase resetting and its relationship to PHG BOLD activation in healthy adults (aged 18-34 years old) navigating a virtual T-maze to find rewards. In the first experiment, both EEG and MEG data revealed a burst of theta power over right-posterior scalp locations following feedback onset (termed right-posterior theta, RPT), and RPT power and measures of phase resetting were sensitive to the subjects spatial trajectory. In Experiment 2, we used probabilistic tractography data from the human connectome project to segment the anterior and posterior PHG based on differential connectivity profiles to other brain regions. This analysis resulted in a PHG subdivision consisting of four distinct anterior and two posterior PHG clusters. Next, a series of linear mixed effects models based on simultaneous EEG-fMRI data revealed that single-trial RPT peak power significantly predicted single-trial hemodynamic responses in two clusters within the posterior PHG and one in the anterior PHG. This coupling between RPT power and PHG BOLD was exclusive to trials performed during maze navigation, and not during a similar task devoid of the spatial context of the maze. These findings highlight a role of PHG theta phase resetting for the purpose of encoding salient information during goal-directed spatial navigation. Taken together, RPT during virtual navigation integrates experimental, computational, and theoretical research of PHG function in animals with human cognitive electrophysiology studies and clinical research on memory-related disorders such as Alzheimers disease.

neuroscience↗

bioRxiv2023

Neurocognitive Dynamics of Preparatory and Adaptive Cognitive Control: Insights from Mass-Univariate and Multivariate Pattern Analysis of EEG data

Cognitive control encompasses a set of basic perceptual and reasoning processes that help us align thoughts and actions with goals. While a growing body of research indicates that these processes can be independently engaged and tuned to fit different tasks (e.g., behavioural preparation vs behavioural adaptation), the dynamic interplay of these processes and their functional timing within the information stream, remains elusive. In this study, we used a combination of mass-univariate and multivariate pattern analysis to examine electroencephalography data from 52 participants, recorded during performance of the Dot Pattern Expectancy Task (DPX), a task designed to assess both preparatory and adaptive cognitive control. Contrary to the notion of isolated neural signatures for either cognitive control mode, our data indicates that cognitive control engages a sequence of distinct yet partially overlapping brain activation patterns. Preparatory cue-stimuli evoked early transient occipital-parietal amplitude responses that were followed by enhanced sustained central-parietal and fronto-central amplitude responses. Similarly, adaptive probe-stimuli evoked enhanced early transient occipital-parietal amplitude responses, but these were followed by enhanced transient, fronto-central and central parietal amplitude responses. Moreover, we found significant relationships between the magnitude of the central-parietal and fronto-central amplitude response pattern and behavioural performance in the DPX. This research not only extends prior work but also offers valuable insights into the functional timing and organisation of the neurocognitive processes underpinning both preparatory and adaptive cognitive control.

neuroscience↗