Biology subjects

Schuhmann, T.

Publications and source records attributed to Schuhmann, T..

8 recordsLinked to original sources

bioRxiv2025

Alpha Oscillatory Imbalance Predicts Attention Deficits in Visuospatial Neglect

Background and ObjectivesVisuospatial neglect (VSN) is a common consequence of unilateral stroke, characterized by reduced awareness on the contralesional side of space. This study examines resting-state electrophysiological mechanisms underlying VSN, with a focus on interhemispheric differences in alpha-band oscillations and their association with deficits in visual perception and attention. MethodsResting-state EEG was recorded during three-minute eyes-closed and eyes-open periods in VSN patients. Participants also completed a battery of perceptual and attentional assessments, including the Star Cancellation Task, the Computerized Visual Detection Task, and the Line Bisection Task. Measures of alpha activity, specifically amplitude, peak frequency, and fronto-parietal connectivity,were compared between VSN patients and age- and gender-matched healthy controls. Within the VSN group, alpha activity in the lesioned and non-lesioned hemispheres was used to predict task performance. ResultsCompared to healthy controls, VSN patients displayed a distinct resting-state alpha profile, characterized by slower and less synchronized alpha oscillations and reduced fronto-parietal alpha connectivity in the lesioned hemisphere. In contrast, controls showed symmetrical alpha activity across hemispheres. Crucially, the degree of interhemispheric alpha asymmetry in VSN patients consistently predicted attentional impairments across all behavioral tasks. DiscussionVSN is linked to disrupted alpha oscillatory dynamics and interhemispheric imbalance. The extent of alpha desynchronization between hemispheres predicts symptom severity, supporting the interhemispheric competition model of attention. These findings suggest that hyperactive alpha activity in the non-lesioned hemisphere may suppress the lesioned hemisphere, contributing to attentional bias away from the contralesional space.

neuroscience↗

bioRxiv2024

The cardiac, respiratory and gastric rhythms independently modulate corticospinal excitability

Interoception refers to the brains sensing of internal body state and encompasses various bodily systems, notably the cardiac, respiratory and gastric rhythms. Beyond their roles in physiological regulation and emotional states, each of these visceral rhythms has been shown to influence brain activity and cognition, prompting for the development of various interpretative functional frameworks. However, both experimental data and functional hypothesis leave it unclear whether and how each visceral rhythm acts simultaneously and independently on brain activity. Here we address this question by measuring in human participants how the corticospinal excitability of the motor system varies with the phase of each of the three visceral rhythms. We applied single pulse Transcranial Magnetic Stimulation (TMS) over the hand region in primary motor cortex to elicit Motor Evoked Potentials (MEP), whose amplitude reflects corticospinal excitability, and tested whether MEP amplitude depends on the phase of the simultaneously measured cardiac, respiratory and gastric rhythms. All three visceral rhythms were coupled to motor excitability with similar effect sizes at the group level. However, we found no relation between coupling strengths: participants displaying high coupling with one organ did not necessarily display high coupling to the other organs. These results indicate that independent mechanisms could underly the coupling between the cardiac, respiratory and gastric rhythm and motor excitability. We further introduce the concept of individual interoceptive profiles, and show that such interoceptive profiles obtained from objective coupling strength measures were not explained by self-reported awareness of the organ. Altogether our results call for refined specifications of the frameworks offering a functional or clinical interpretation of viscera-brain coupling taking into account both independent mechanisms and individual interoceptive profiles.

neuroscience↗

bioRxiv2022

Assessing TMS-evoked cognitive network responses depending on neurocognitive and oscillatory brain state: A simultaneous TMS-EEG-fMRI project

Human cognition arises from information exchange within and between functionally connected brain networks. Alterations in such signal propagation across networks are linked to numerous disorders. Brain-wide signal propagation can be experimentally studied with simultaneous transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI), where TMS pulses introduce a signal at a certain network node and fMRI charts its propagation through the network. Yet, this approach ignores the fact that the (network) impact of a TMS pulse depends on brain state, where brain state fluctuates spontaneously from moment to moment (e.g. oscillatory state) as well as depending on what a participant does (neurocognitive state). Here, we assessed TMS-evoked fMRI activations as a function of neurocognitive state (eyes open versus eyes closed in complete darkness) and oscillatory state (low versus high pre-TMS alpha power, as measured with simultaneous electroencephalography (EEG)). We applied supra-versus sub-threshold triple-pulse TMS to the right posterior parietal cortex in eight participants, while simultaneously recording EEG and fMRI during two different ocular states. In this first application of the multimodal TMS-EEG-fMRI paradigm to a cognitive network hub, we did not find evidence for a brain state modulation of TMS-induced signal propagation. Instead, we found state-independent TMS-evoked fMRI responses mostly in sensory areas such as the insula, superior temporal gyrus, anterior cingulate cortex, and thalamus, but also in the frontal eye fields. Interestingly, neurocognitive state did seem to modulate the fMRI response to indirect TMS effects such as sensory stimulation. These results lead to several important insights for future cognitive multimodal TMS experiments.

neuroscience↗

bioRxiv2020

Reduced risk-taking behavior during frontal oscillatory theta band neurostimulation

BackgroundMost of our decisions involve a certain degree of risk regarding the outcomes of our choices. People vary in the way they make decisions, resulting in different levels of risk-taking behavior. These differences have been linked to prefrontal theta band activity. However, a direct functional relationship between prefrontal theta band activity and risk-taking has not yet been demonstrated. ObjectiveWe used noninvasive brain stimulation to test the functional relevance of prefrontal oscillatory theta activity for the regulatory control of risk-taking behavior. MethodsIn a within-subject experiment, 32 healthy participants received theta [4-8 Hertz (Hz)], gamma (30-50 Hz), and sham transcranial alternating current stimulation (tACS) over the left prefrontal cortex (lPFC). During stimulation, participants completed a task assessing their risk-taking behavior as well as response times and sensitivity to value and outcome probabilities. Electroencephalography (EEG) was recorded before and immediately after stimulation. ResultsTheta-band, but not gamma-band or sham, tACS led to a significant reduction in risk-taking behavior, indicating a frequency-specific effect of prefrontal brain stimulation on the modulation of risk-taking behavior. Moreover, theta-band stimulation led to increased response times and decreased sensitivity to reward values. EEG data analyses did not show an increase in power in the stimulated frequencies. ConclusionThese findings provide direct empirical evidence for the effects of prefrontal theta-band stimulation on behavioral risk-taking regulation.

neuroscience↗

bioRxiv2020

Transcranial Magnetic stimulation (TMS) modulates functional activity of SH-SY5Y cells: An in vitro model provides support for assumed excitability changes

Repetitive Transcranial Magnetic Stimulation (rTMS) is an established neuromodulation technique, using electromagnetic pulses that, depending on the precise parameters, are assumed to lead to lasting neural excitability changes. rTMS has widespread applications in both research and therapy, where it has been FDA approved and is considered a first-line treatment for depression, according to recent North American and European guidelines. However, these assumed excitability effects are often difficult to replicate, and highly unreliable on the single subject/patient level. Given the increasing application of rTMS, especially in clinical practice, the absence of a method to unequivocally determine effects of rTMS on human neuronal excitability is problematic. We have taken a first step in addressing this bottleneck, by administering excitatory and inhibitory rTMS protocols, iTBS and cTBS, to a human in vitro neuron model; differentiated SH-SY5Y cells. We use live calcium imaging to assess changes in neural activity following stimulation, through quantifying fluorescence response to chemical depolarization. We found that iTBS and cTBS have opposite effects on fluorescence response; with iTBS increasing and cTBS decreasing response to chemical depolarization. Our results are promising, as they provide a clear demonstration of rTMS after-effects in a living human neuron model. We here present an in-vitro live calcium imaging setup that can be further applied to more complex human neuron models, for developing and evaluating subject/patient-specific brain stimulation protocols.

neuroscience↗

bioRxiv2020

Frequency-specific transcranial neuromodulation of oscillatory alpha power alters and predicts human visuospatial attention performance

Unilateral transcranial alternating current stimulation (tACS) at alpha frequency modulates the locus of spatial attention. However, the neural mechanisms by which tACS influences spatial attention remain poorly understood. Here, we applied high-definition tACS at the individual alpha frequency (IAF), two control frequencies (IAF+/-2Hz) and sham to the left posterior parietal cortex and measured its effects on visuospatial attention performance as well as alpha power (using electroencephalography, EEG). Our results revealed a leftward lateralization of alpha power relative to sham. At a high value of leftward alpha lateralization, we also observed a leftward attention bias, which differed from sham. Moreover, the magnitude of the alpha lateralization effect predicted the attention bias. These effects occurred for tACS at IAF but not for the control frequencies. This suggests that tACS operates through oscillatory interactions with ongoing brain rhythms in line with the synchronization theory. Our results also highlight the importance of personalized stimulation protocols, especially in potential clinical settings.

neuroscience↗

bioRxiv2020

Cheminformatics Analysis of Natural Product Scaffolds: Comparison of Scaffolds Produced by Animals, Plants, Fungi and Bacteria

Natural products (NPs) have evolved over a very long natural selection process to form optimal interactions with biologically relevant macromolecules. NPs are therefore an extremely useful source of inspiration for the design of new drugs. In the present study we report the results of a cheminformatics analysis of a large database of NP structures focusing on their scaffolds. First, general differences between NP scaffolds and scaffolds from synthetic molecules are discussed, followed by a comparison of the properties of scaffolds produced by different types of organisms. Scaffolds produced by plants are the most complex and those produced by bacteria differ in many structural features from scaffolds produced by other organisms. The results presented here may be used as a guidance in selection of scaffolds for the design of novel NP-like bioactive structures or NP-inspired libraries.

bioinformatics↗

bioRxiv2019

Left parietal tACS at alpha frequency induces a shift of visuospatial attention

BackgroundVoluntary shifts of visuospatial attention are associated with a lateralization of occipitoparietal alpha power (7-13Hz), i.e. higher power in the hemisphere ipsilateral and lower power contralateral to the locus of attention. Recent noninvasive neuromodulation studies demonstrated that alpha power can be experimentally increased using transcranial alternating current stimulation (tACS).\n\nObjective/HypothesisWe hypothesized that tACS at alpha frequency over the left parietal cortex induces shifts of attention to the left hemifield. However, spatial attention shifts not only occur voluntarily (endogenous), but also stimulus-driven (exogenous). In order to study the task-specificity of the potential effects of tACS on attentional processes, we administered three conceptually different spatial attention tasks.\n\nMethods36 healthy volunteers were recruited from an academic environment. In two seperate sessions, we applied either high-density tACS at 10Hz, or sham tACS, for 35-40 minutes to their left parietal cortex. We systematically compared performance on endogenous attention, exogenous attention, and stimulus detection tasks.\n\nResultsIn the Endogenous attention task, we found a greater leftward bias in reaction times during left parietal 10Hz tACS as compared to sham. There were no stimulation effects in the exogenous attention or stimulus detection task.\n\nConclusionThe study shows that high-density tACS at 10Hz can be used to modulate visuospatial attention performance. The tACS effect is task-specific, indicating that not all forms of attention are equally susceptible to the stimulation.

neuroscience↗