Author name cluster

Markus Butz

Possible papers associated with this exact author name in Arrow. This page groups case-insensitive exact name matches and is not a full identity disambiguation profile.

7 papers

1 author row

YNICL Journal 2025 Journal Article

Modulations of thalamo-cortical coupling during voluntary movement in patients with essential tremor

Alexandra Steina
Sarah Sure
Markus Butz
Jan Vesper
Alfons Schnitzler
Jan Hirschmann

The ventral intermediate nucleus of the thalamus (VIM) is the main thalamic hub for cerebellar inputs and the primary deep brain stimulation target in essential tremor (ET). As such, it presumably plays a critical role in motor control. However, this structure is rarely studied in humans, and existing studies mostly focus on tremor. Here, we studied neural oscillations in the VIM and their coupling to cortical oscillations during voluntary movement. We investigated thalamo-cortical coupling, combining recordings of thalamic local field potentials and magnetoencephalography, in 10 ET patients with externalized deep brain stimulation electrodes. During the recording, patients repeatedly pressed a button in response to a visual cue. In a whole-brain analysis of VIM-cortex coherence, we contrasted activity during pre-movement baseline and button pressing. Button pressing was associated with a bilateral decrease of thalamic alpha (8-12 Hz) and beta (13-21 Hz) power and a contralateral gamma (35-90 Hz) power increase. Alpha/low-beta (8-20 Hz) coherence decreased during movement. This effect localized to the supplementary motor area and premotor cortex. A high-beta (21-35 Hz) coherence increase occurred in the same region but was more focal than the suppression. Pre-movement levels of thalamo-cortex low-beta coherence correlated with reaction time. Our results demonstrate that voluntary movement is associated with modulations of behaviourally relevant thalamic coupling, primarily to premotor areas. We observed a clear distinction between low- and high-beta frequencies and our results suggest that the concept of "antikinetic" beta oscillations, originating from research on Parkinson's disease, is transferable to ET.

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YNICL Journal 2019 Journal Article

Chemical exchange saturation transfer imaging in hepatic encephalopathy

Helge Jörn Zöllner
Markus Butz
Markus Jördens
Nur-Deniz Füllenbach
Dieter Häussinger
Benjamin Schmitt
Hans-Jörg Wittsack
Alfons Schnitzler

Hepatic encephalopathy (HE) is a common complication in liver cirrhosis and associated with an invasion of ammonia into the brain through the blood-brain barrier. Resulting higher ammonia concentrations in the brain are suggested to lead to a dose-dependent gradual increase of HE severity and an associated impairment of brain function. Amide proton transfer-weighted (APTw) chemical exchange saturation transfer (CEST) imaging has been found to be sensitive to ammonia concentration. The aim of this work was to study APTw CEST imaging in patients with HE and to investigate the relationship between disease severity, critical flicker frequency (CFF), psychometric test scores, blood ammonia, and APTw signals in different brain regions. Whole-brain APTw CEST images were acquired in 34 participants (14 controls, 20 patients (10 minimal HE, 10 manifest HE)) on a 3 T clinical MRI system accompanied by T1 mapping and structural images. T1 normalized magnetization transfer ratio asymmetry analysis was performed around 3 ppm after B0 and B1 correction to create APTw images. All APTw images were spatially normalized into a cohort space to allow direct comparison. APTw images in 6 brain regions (cerebellum, occipital cortex, putamen, thalamus, caudate, white matter) were tested for group differences as well as the link to CFF, psychometric test scores, and blood ammonia. A decrease in APTw intensities was found in the cerebellum and the occipital cortex of manifest HE patients. In addition, APTw intensities in the cerebellum correlated positively with several psychometric scores, such as the fine motor performance scores MLS1 for hand steadiness / tremor (r = 0. 466; p =. 044) and WRT2 for motor reaction time (r = 0. 523; p =. 022). Moreover, a negative correlation between APTw intensities and blood ammonia was found for the cerebellum (r = −0. 615; p =. 007) and the occipital cortex (r = −0. 478; p =. 045). An increase of APTw intensities was observed in the putamen of patients with minimal HE and correlated negatively with the CFF (r = −0. 423; p =. 013). Our findings demonstrate that HE is associated with regional differential alterations in APTw signals. These variations are most likely a consequence of hyperammonemia or hepatocerebral degeneration processes, and develop in parallel with disease severity.

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YNICL Journal 2018 Journal Article

Connecting occipital alpha band peak frequency, visual temporal resolution, and occipital GABA levels in healthy participants and hepatic encephalopathy patients

Thomas J. Baumgarten
Julia Neugebauer
Georg Oeltzschner
Nur-Deniz Füllenbach
Gerald Kircheis
Dieter Häussinger
Joachim Lange
Hans-Jörg Wittsack

Recent studies have proposed a connection between the individual alpha band peak frequency and the temporal resolution of visual perception in healthy human participants. This connection rests on animal studies describing oscillations in the alpha band as a mode of phasic thalamocortical information transfer for low-level visual stimuli, which critically relies on GABAergic interneurons. Here, we investigated the interplay of these parameters by measuring occipital alpha band peak frequency by means of magnetoencephalography, visual temporal resolution by means of behavioral testing, and occipital GABA levels by means of magnetic resonance spectroscopy. Importantly, we investigated a sample of healthy participants and patients with varying grades of hepatic encephalopathy, which are known to exhibit decreases in the investigated parameters, thus providing an increased parameter space. We found that occipital alpha band peak frequency and visual temporal resolution were positively correlated, i.e., higher occipital alpha band peak frequencies were on average related to a higher temporal resolution. Likewise, occipital alpha band peak frequency correlated positively with occipital GABA levels. However, correlations were significant only when both healthy participants and patients were included in the analysis, thereby indicating a connection of the measures on group level (instead of the individual level). These findings provide new insights into neurophysiological and neurochemical underpinnings of visual perception.

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YNIMG Journal 2018 Journal Article

Unilateral deep brain stimulation suppresses alpha and beta oscillations in sensorimotor cortices

Omid Abbasi
Jan Hirschmann
Lena Storzer
Tolga Esat Özkurt
Saskia Elben
Jan Vesper
Lars Wojtecki
Georg Schmitz

Deep brain stimulation (DBS) is an established therapy to treat motor symptoms in movement disorders such as Parkinson's disease (PD). The mechanisms leading to the high therapeutic effectiveness of DBS are poorly understood so far, but modulation of oscillatory activity is likely to play an important role. Thus, investigating the effect of DBS on cortical oscillatory activity can help clarifying the neurophysiological mechanisms of DBS. Here, we aimed at scrutinizing changes of cortical oscillatory activity by DBS at different frequencies using magnetoencephalography (MEG). MEG data from 17 PD patients were acquired during DBS of the subthalamic nucleus (STN) the day after electrode implantation and before implanting the pulse generator. We stimulated the STN unilaterally at two different stimulation frequencies, 130 Hz and 340 Hz using an external stimulator. Data from six patients had to be discarded due to strong artefacts and two other datasets were excluded since these patients were not able to finalize the paradigm. After DBS artefact removal, power spectral density (PSD) values of MEG were calculated for each individual patient and averaged over the group. DBS at both 130 Hz and 340 Hz led to a widespread suppression of cortical alpha/beta band activity (8–22 Hz) specifically over bilateral sensorimotor cortices. No significant differences were observed between the two stimulation frequencies. Our finding of a widespread suppression of cortical alpha/beta band activity is particularly interesting as PD is associated with pathologically increased levels of beta band activity in the basal ganglia-thalamo-cortical circuit. Therefore, suppression of such oscillatory activity might be an essential effect of DBS for relieving motor symptoms in PD and can be achieved at different stimulation frequencies above 100 Hz.

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YNIMG Journal 2012 Journal Article

Lowered frequency and impaired modulation of gamma band oscillations in a bimodal attention task are associated with reduced critical flicker frequency

Nina Kahlbrock
Markus Butz
Elisabeth S. May
Meike Brenner
Gerald Kircheis
Dieter Häussinger
Alfons Schnitzler

Visual attention is associated with occipital gamma band activity. While gamma band power can be modulated by attention, the frequency of gamma band activity is known to decrease with age. The present study tested the hypothesis that reduced visual attention is associated with a change in induced gamma band activity. To this end, 26 patients with liver cirrhosis and 8 healthy controls were tested. A subset of patients showed symptoms of hepatic encephalopathy (HE), a frequent neuropsychiatric complication in liver disease, which comprises a gradual increase of cognitive dysfunction including attention deficits. All participants completed a behavioral task requiring shifts of attention between simultaneously presented visual and auditory stimuli. Brain activity was recorded using magnetoencephalography (MEG). The individual critical flicker frequency (CFF) was assessed as it is known to reliably reflect the severity of HE. Results showed correlations of behavioral data and HE severity, as indexed by CFF. Individual visual gamma band peak frequencies correlated positively with the CFF (r=0. 41). Only participants with normal, but not with pathological CFF values showed a modulation of gamma band power with attention. The present results suggest that CFF and attentional performance are related. Moreover, a tight relation between the CFF and occipital gamma band activity both in frequency and power is shown. Thus, the present study provides evidence that a reduced CFF in HE, a disease associated with attention deficits, is closely linked to a slowing of gamma band activity and impaired modulation of gamma band power in a bimodal attention task.

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YNIMG Journal 2012 Journal Article

Pre- and post-stimulus alpha activity shows differential modulation with spatial attention during the processing of pain

Elisabeth S. May
Markus Butz
Nina Kahlbrock
Nienke Hoogenboom
Meike Brenner
Alfons Schnitzler

Extensive work using magneto- and electroencephalography (M/EEG) suggests that cortical alpha activity represents a top-down controlled gating mechanism employed by processes like attention across different modalities. However, it is not yet clear to what extent this presumed gating function of alpha activity also applies to the processing of pain. In the current study, a spatial attention paradigm was employed requiring subjects to attend to painful laser stimuli on one hand while ignoring stimuli on the other hand. Simultaneously, brain activity was recorded with MEG. In order to disentangle pre- and post-stimulus effects of attention, alpha activity was analyzed during time windows in anticipation of and in response to painful laser stimulation. Painful laser stimuli led to a suppression of alpha activity over both ipsi- and contralateral primary somatosensory areas irrespective if they were attended or ignored. Spatial attention was associated with a lateralization of anticipatory pre-stimulus alpha activity. Alpha activity was lower over primary somatosensory areas when the contralateral hand was attended compared to when the ipsilateral hand was attended, in line with the notion that oscillatory alpha activity regulates the flow of incoming information by engaging and/or disengaging early sensory areas. On the contrary, post-stimulus alpha activity, for stimuli on either hand, was consistently decreased with attention over contralateral areas. Most likely, this finding reflects an increased cortical activation and enhanced alerting if a painful stimulus is attended. The present results show that spatial attention results in a modulation of both pre- and post-stimulus alpha activity associated with pain. This flexible regulation of alpha activity matches findings from other modalities. We conclude that the assumed functional role of alpha activity as a top-down controlled gating mechanism includes pain processing and most likely represents a unified mechanism used throughout the brain.

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YNIMG Journal 2012 Journal Article

Sustained gamma band synchronization in early visual areas reflects the level of selective attention

Nina Kahlbrock
Markus Butz
Elisabeth S. May
Alfons Schnitzler

Cortical gamma band synchronization is associated with attention. Accordingly, directing attention to certain visual stimuli modulates gamma band activity in visual cortical areas. However, gradual effects of attention and behavior on gamma band activity in early visual areas have not yet been reported. In the present study, the degree of selective visual attention was gradually varied in a cued bimodal reaction time paradigm using audio-visual stimuli. Brain activity was recorded with magnetoencephalography (MEG) and analyzed with respect to time, frequency, and location of strongest response. Reaction times to visual and auditory stimuli reflected three presumed graded levels of visual attention (high, medium, and low). MEG data showed sustained gamma band synchronization in all three conditions in early visual areas (V1 and V2), while the intensity of gamma band synchronization increased with the level of visual attention (from low to high). Differences between conditions were seen for up to 1600ms. The current results show that in early visual areas the level of gamma band synchronization is related to the level of attention directed to a visual stimulus. These gradual and long-lasting effects highlight the key role of gamma band synchronization in early visual areas for selective attention.

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