Author name cluster

Susanne Karch

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.

5 papers

1 author row

YNICL Journal 2023 Journal Article

Neurofunctional differences and similarities between persistent postural-perceptual dizziness and anxiety disorder

Maximilian Maywald
Oliver Pogarell
Susanne Levai
Marco Paolini
Nadja Tschentscher
Boris Stephan Rauchmann
Daniela Krause
Sophia Stöcklein

INTRODUCTION: Persistent postural-perceptual dizziness (PPPD) (ICD-11) and anxiety disorders (ANX) share behavioural symptoms like anxiety, avoidance, social withdrawal, hyperarousal, or palpitation as well as neurological symptoms like vertigo, stance and gait disorders. Furthermore, previous studies have shown a bidirectional link between vestibulo-spatial and anxiety neural networks. So far, there have been no neuroimaging-studies comparing these groups. OBJECTIVES: The aim of this explorative study was to investigate differences and similarities of neural correlates between these two patient groups and to compare their findings with a healthy control group. METHODS: 63 participants, divided in two patient groups (ANX = 20 and PPPD = 14) and two sex and age matched healthy control groups (HC-A = 16, HC-P = 13) were included. Anxiety and dizziness related pictures were shown during fMRI-measurements in a block-design in order to induce emotional responses. All subjects filled in questionnaires regarding vertigo (VSS, VHQ), anxiety (STAI), depression (BDI-II), alexithymia (TAS), and illness-perception (IPQ). After modelling the BOLD response with a standard canonical HRF, voxel-wise t-tests between conditions (emotional-negative vs neutral stimuli) were used to generate statistical contrast maps and identify relevant brain areas (pFDR 30 voxels). ROI-analyses were performed for amygdala, cingulate gyrus, hippocampus, inferior frontal gyrus, insula, supramarginal gyrus and thalamus (p ≤ 0.05). RESULTS: Patient groups differed from both HC groups regarding anxiety, dizziness, depression and alexithymia scores; ratings of the PPPD group and the ANX group did differ significantly only in the VSS subscale 'vertigo and related symptoms' (VSS-VER). The PPPD group showed increased neural responses in the vestibulo-spatial network, especially in the supramarginal gyrus (SMG), and superior temporal gyrus (STG), compared to ANX and HC-P group. The PPPD group showed increased neural responses compared to the HC-P group in the anxiety network including amygdala, insula, lentiform gyrus, hippocampus, inferior frontal gyrus (IFG) and brainstem. Neuronal responses were enhanced in visual structures, e.g. fusiform gyrus, middle occipital gyrus, and in the medial orbitofrontal cortex (mOFC) in healthy controls compared to patients with ANX and PPPD, and in the ANX group compared to the PPPD group. CONCLUSIONS: These findings indicate that neuronal responses to emotional information in the PPPD and the ANX group are comparable in anxiety networks but not in vestibulo-spatial networks. Patients with PPPD revealed a stronger neuronal response especially in SMG and STG compared to the ANX and the HC group. These results might suggest higher sensitivity and poorer adaptation processes in the PPPD group to anxiety and dizziness related pictures. Stronger activation in visual processing areas in HC subjects might be due to less emotional and more visual processing strategies.

Details DOI

YNIMG Journal 2010 Journal Article

Separating distinct aspects of the voluntary selection between response alternatives: N2- and P3-related BOLD responses

Susanne Karch
Regina Feuerecker
Gregor Leicht
Thomas Meindl
Irmgard Hantschk
Valerie Kirsch
Matthias Ertl
Jürgen Lutz

Voluntary selection between response alternatives belongs to cognitive abilities controlling and regulating goal-directed behaviour. Voluntary selection processes are associated with increased neural activity, especially in medial and lateral frontal brain regions as well as the inferior parietal gyrus. However, the precise function of each brain region as well as the spatiotemporal characteristic of the brain regions involved is not yet clear. The aim of the present study was to disentangle distinct aspects of voluntary selection and their underlying neural processes. Hence, event-related potentials (ERPs) and functional MRI data were acquired simultaneously. Brain regions modulated by the task-induced amplitude variation of ERPs (N2, P3) were identified. The results showed N2-related hemodynamic responses, especially in medial and lateral frontal brain regions. Among other things, medial frontal brain regions are related to conflict monitoring, control of voluntary action and decision making. By contrast, the P3-amplitude proved to be predominantly related to increased BOLD responses in the temporo-parietal junction and lateral frontal brain regions. These brain regions are thought to play a decisive role in an attentional network involved in detecting auditory and visual stimuli. Overall, the results of the study indicated a whole network of brain regions to be associated with voluntary selection processes. In addition, at least some frontal brain regions seemed to be involved at an earlier stage than temporo-parietal regions, probably indicating a top-down process.

Details DOI

YNIMG Journal 2009 Journal Article

EEG-vigilance and BOLD effect during simultaneous EEG/fMRI measurement

Sebastian Olbrich
Christoph Mulert
Susanne Karch
Maja Trenner
Gregor Leicht
Oliver Pogarell
Ulrich Hegerl

Different EEG-vigilance stages from full alertness to sleep onset can be separated during rest. Also fMRI research recently focused on the resting condition and identified several resting state networks. In order to deepen the understanding of different levels of global brain function from relaxed wakefulness to sleep onset the association between EEG-vigilance stages and BOLD signals was analysed. EEG-vigilance stages were attributed to consecutive 3-sec-EEG-segments by an algorithm using topographic and spectral information. Results of the classification were validated by analysing the heart rates during the different brain states. Vigilance stages served as regressors for the analysis of the simultaneously acquired fMRI data. Additionally resting state networks were derived from the fMRI data using independent component analysis (ICA). Also vigilance associated brain activity revealed by EEG-based standardized low resolution tomography (sLORETA) was compared to the results of the fMRI analysis. Results showed increased BOLD signal in the occipital cortex, the anterior cingulate cortex, the frontal cortex, the parietal cortices and the temporal cortices and decreasing BOLD signals in the thalamus and the frontal cortex for declining vigilance stages (A2, A3, B1, B2/B3) in comparison to the high vigilance stage A1. Resting state networks revealed a spatial overlap with the vigilance stage associated BOLD maps in conjunction analyses. sLORETA showed increased neuroelectric alpha activity at the occipital cortex comparable to occipital BOLD signal decreases when comparing stage A with stage B. Different EEG-vigilance stages during rest are associated with pronounced differences of BOLD signals in several brain areas which partly correspond to the resting state networks. For cognitive fMRI-research it therefore seems important to pay attention to vigilance switches in order to separate vigilance associated BOLD signal changes from those specifically related to cognition.

Details DOI

YNIMG Journal 2008 Journal Article

Single-trial coupling of EEG and fMRI reveals the involvement of early anterior cingulate cortex activation in effortful decision making

Christoph Mulert
Christian Seifert
Gregor Leicht
Valerie Kirsch
Matthias Ertl
Susanne Karch
Matthias Moosmann
Jürgen Lutz

While the precise role of the anterior cingulate cortex (ACC) is still being discussed, it has been suggested that ACC activity might reflect the amount of mental effort associated with cognitive processing. So far, not much is known about the temporal dynamics of ACC activity in effort-related decision making or auditory attention, because fMRI is limited concerning its temporal resolution and electroencephalography (EEG) is limited concerning its spatial resolution. Single-trial coupling of EEG and fMRI can be used to predict the BOLD signal specifically related to amplitude variations of electrophysiological components. The striking feature of single-trial coupling is its ability to separate different aspects of the BOLD signal according to their specific relationship to a distinct neural process. In the present study we investigated 10 healthy subjects with a forced choice reaction task under both low and high effort conditions and a control condition (passive listening) using simultaneous EEG and fMRI. We detected a significant effect of mental effort only for the N1 potential, but not for the P300 potential. In the fMRI analysis, ACC activation was present only in the high effort condition. We used single-trial coupling of EEG and fMRI in order to separate information specific to N1-amplitude variations from the unrelated BOLD response. Under high effort conditions we were able to detect circumscribed BOLD activations specific to the N1 potential in the ACC (t =4. 7) and the auditory cortex (t =6. 1). Comparing the N1-specific BOLD activity of the high effort condition versus the control condition we found only activation of the ACC (random effects analysis, corrected for multiple comparisons, t =4. 4). These findings suggest a role of early ACC activation in effort-related decision making and provide a direct link between the N1 component and its corresponding BOLD signal.

Details DOI

YNIMG Journal 2005 Journal Article

Sound level dependence of the primary auditory cortex: Simultaneous measurement with 61-channel EEG and fMRI

Christoph Mulert
Lorenz Jäger
Sebastian Propp
Susanne Karch
Sylvère Störmann
Oliver Pogarell
Hans-Jürgen Möller
Georg Juckel

Sound level dependence has been investigated for years with event-related potentials (ERP). A serotonergic modulation of the sound level dependence only of the primary auditory cortex but not of the auditory association cortex has been suggested by a number of clinical and preclinical studies. Therefore, a precise covering of the activity of the primary auditory cortex seems necessary if sound level dependence is used as an indicator of the central serotonergic system. Recent fMRI studies described a pronounced sound level dependence only in the Heschl gyrus/primary auditory cortex but not in auditory association areas. In the present simultaneous 61-channel EEG and fMRI study investigating fourteen healthy subjects, we found a high correlation between the loudness-dependent change of the extent of fMRI activation (number of activated voxels) and the corresponding changes of the mean current source density within the same region of interest covering the primary auditory cortex (r = 0. 84, P < 0. 001). Our findings suggest a close relationship between the fMRI signal and event-related potential activity. In addition, the correspondence of the ERP-based data and the fMRI results further supports the validity of the ERP localization approach.

Details DOI