Non-pharmacological approaches such as novel brain stimulation techniques are gaining more and more importance as add-on treatment for major mental disorders. In our symposium,
Jonas Rauh, University Medical Center Hamburg-Eppendorf, will report an ongoing multi-center electroencephalography (EEG) study using frontal high-density theta-tACS (5Hz) of the dorsolateral prefrontal cortex during working memory (WM) performance. Sham-controlled theta-tACS effects on WM deficits and WM-related EEG alterations in different stages of schizophrenia (ultra-high risk for psychosis, first-episode and chronic states) will be evaluated.
Christoph Mulert, Center for Psychiatry and Psychotherapy, JLU Gießen, will illustrate the role of interhemispheric connectivity for auditory perception and auditory verbal hallucinations (AVH). His data demonstrate tACS in the gamma-band range (40Hz) to interfer with interhemispheric connectivity mechanisms, modulate auditory perception and develop a framework for new therapeutic treatment options for AVH.
We will then discuss innovative approaches to facilitate and understand stimulation effects by personalized stimulation protocols derived from novel forward and inverse modeling in electroencephalography (EEG) and magnetoencephalography (MEG) source imaging (ESI, MSI):
Jan-Ole Radecke, Universities of Hamburg and Lübeck, will introduce a tACS-study with individual targeting of neural alpha activity in the parietal cortex during visuo-spatial attention. Behavioral data, finite-element simulations of transcranial electric fields, and EEG source imaging (ESI) data will illustrate tACS-modulation of the dorsofrontal attention network.
Carsten Wolters, University of Münster, will report effects of combined E/MSI targeting and optimized multi-channel tDCS, which significantly reduced focal epileptic activity in a double-blind sham-controlled N-of-1 trial. We will close with an outlook on broader use of tES applications in the field of mental disorders
13:30 Uhr
Frontal high density theta-tACS of the working memory network in patients with schizophrenia
J. Rauh (Hamburg, DE)
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Autor:in:
J. Rauh (Hamburg, DE)
Working memory (WM) deficits are a core symptom of schizophrenia. Altered WM functions can already be seen in early stages of the disease. A vast of neurophysiological and imaging data underline the relevance of theta oscillations and activation of fronto-parietal WM network during WM processes. Targeting these disturbances with non-invasive brain stimulation techniques such as transcranial electrical stimulation seems promising. In particular with transcranial alternating current stimulation (tACS) exists an approach which bases on modulation of endogenous brain oscillations.
In our work, we applied high-density transcranial theta-band tACS over the left DLPFC to patients with schizophrenia and healthy controls. In order to reveal direct neurophysiolocial effects of the stimulation EEG is recorded simultaneously during the tACS.
13:52 Uhr
Role of interhemispheric connectivity for auditory perception and auditory verbal hallucinations derived by tACS
C. Mulert (Gießen, DE)
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C. Mulert (Gießen, DE)
Auditory verbal hallucinations (AVH) are hallmark symptoms of schizophrenia and have been linked to abnormal activation, connectivity and integration within the auditory, language, and memory brain networks. The interhemispheric miscommunication theory of AVH is based on a steadily growing number of studies using a variety of modalities (EEG, fMRI, DTI) reporting that both altered integrity of the interhemispheric auditory pathways and disturbed functional gamma-band synchrony between right and left auditory cortices significantly contribute to abnormal auditory processing and the emergence of AVH. Here we report evidence that high densitiy gamma-band tACS can influence interhemispheric connectivity / gamma-band coupling and related auditory perception. This approach is discussed with regard to the treatment of AVH in schizophrenia.
14:14 Uhr
Personalized transcranial alternating current stimulation (tACS) modulates attention
J. Radecke (Lübeck, DE)
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Autor:innen:
J. Radecke (Lübeck, DE)
R. Lencer (DE)
T. Schneider (DE)
TACS in the alpha frequency range has been shown to modulate behavior during intentional shifts of visuo-spatial attention. A modulation of posterior neural alpha activity has been proposed as effector of the attention modulation induced by TACS. However, TACS-applications during visuo-spatial attention studies show limited replicability and small effect sizes, at least partly due to individual brain anatomy and thus varying electric fields induced by TACS.
In the presented study highly sophisticated personalized TACS was applied to account for anatomical variability and to test the hypothesis whether alpha-TACS modulates attention behavior and posterior alpha power. Individual sources of neural alpha activity in left and right parietal cortex were targeted. Behavioral data and EEG after-effects were assessed in conjunction with individual finite-element simulations of TACS-induced electric fields.
We found that TACS modulated attention only when targeting left but not right parietal cortex, while electric field simulations showed no asymmetry between left and right parietal TACS. Together this indicates a rather functional asymmetry of the dorsofrontal attention network during TACS. Second, instead of a modulation of posterior neural alpha power, we found that TACS-induced stimulus-related evoked activity was modulated in left premotor cortex. In addition, correlations of the electric field and behavior indicated a critical role of the left premotor cortex during TACS-modulation of visuo-spatial attention. In sum, results suggest an increased susceptibility of the left dorsofrontal attention network, including the parietal and premotor cortex, to subtle neuromodulation by TACS.
Based on this application of personalized TACS, implications for the advantages and pitfalls of personalized transcranial electric stimulation protocols for experimental applications with a clinical focus are discussed.
14:36 Uhr
Individualized EEG/MEG targeting and optimized multi-channel transcranial electric stimulation in focal epilepsy
C. Wolters (Münster, DE)
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Autor:innen:
C. Wolters (Münster, DE)
M. Antonakakis (Chania, GR)
F. Kaiser (DE)
S. Rampp (DE)
C. Kellinghaus (DE)
S. Kovac (DE)
J. Gross (DE)
G. Möddel (DE)
The goal of this work is to assess the efficacy of targeted (by combined MEG/EEG source analysis) and optimized multi-channel transcranial direct current stimulation (mc-tDCS) as therapy for focal epilepsy in a double blind sham-controlled N-of-1 trial. Targeted and optimized mc-tDCS was applied as alternative therapy in a 20 year-old pharmaco-resistant epilepsy patient. For mc-tDCS optimization we used our recently developed algorithm - Distributed Constrained Maximum Intensity (D-CMI) (Khan et al., 2022, doi: 10.1016/j.clinph.2021.10.016) - on a target region which was determined by mean of combined MEG/EEG source analysis of averaged interictal epileptiform discharges (IEDs) using realistic and skull-conductivity calibrated finite-element head modeling. A total amplitude of 4 mA was applied twice for 20 minutes, with a pause of 20 minutes in between, for five consecutive days. An Acti-Sham montage (adjacent leads have opposite polarities) was applied with the same regimen as treatment. There was a washout of 5 weeks between the two stimulation weeks.
With regard to interictal activity, targeted D-CMI mc-tDCS led to a highly significant reduction in IED frequency after treatment with median 66% (55.8%± 11.2%, p < 0.00001), while Acti-Sham did not (p > 0.05). The IED source amplitude was decreased by 76% after treatment with D-CMI mc-tDCS while it was only reduced by 29% after treatment with Acti-Sham. Side effects entirely pertained to transient sensations.
With regard to ictal activity, the patient experienced a seizure with decreased severity during the stimulation week.