P111. Exploring the effects of transcranial direct current stimulation on cognitive control training

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Abstracts / Clinical Neurophysiology 129 (2018) e48–e116

Exp. 2 show that the recruitment of the cerebellar-brain connections varies depending on tDCS polarity and CS intensity, suggesting that tDCS differently affects neurons in different layers of the cerebellar cortex. This polarity-specific dependence should be considered for tDCS applications and addressed in future studies. Funded by MercurPr-2015-0010 and SFB1280 (TP A05 and A06).

References Hartwigsen G, Price CJ, Baumgaertner A, Geiss G, Koehnke M, Ulmer S, Siebner HR. The right posterior inferior frontal gyrus contributes to phonological word decisions in the healthy brain: evidence from dual-site TMS. Neuropsychologia 2010;48(10):3155–63. Miniussi C, Harris JA, Ruzzoli M. Modelling non-invasive brain stimulation in cognitive neuroscience. Neurosci Biobehav Rev 2013;37(8):1702–12.

doi:10.1016/j.clinph.2018.04.726 doi:10.1016/j.clinph.2018.04.727

P108. Effects of 10 Hz tACS on phonological language processing—T. Stenner 1,2.*, L. Sierau 1,2, M. Werchowski 1,2, S. Matern 1,2, C. Kaernbach 3,4, M. Siniatchkin 1,2, G. Hartwigsen 5,6, 1,2 1 V. Moliadze ( Schleswig-Holstein University Hospital (UKSH), Christian-Albrechts-Universität, Kiel, Germany , 2 Department of Medical Psychology and Medical Sociology, Kiel, Germany, 3 Chri stian-Albrechts-Universität, Kiel, Germany, 4 Department of Psychology, Kiel, Germany, 5 Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, 6 Department of Neuropsychology, Leipzig, Germany) ⇑

Presenting author.

Introduction: A previous study (Hartwigsen et al., 2010) has shown that 10 Hz rTMS of the left or right posterior inferior frontal gyrus (IFG) impaired performance in a phonological decision-making task. However, it is unclear whether the neurodisruptive effect of 10 HzrTMS is caused by entrainment of alpha-oscillations. To address this issue, the present study investigated the following questions: (1) Are alpha-oscillations in the IFG functionally relevant for phonological processing? (2) Can we enhance alpha activity in the IFG using 10 Hz tACS? and (3) Does enhancement of alpha activity cause behavioral disruption? Methods: 24 right-handed, healthy participants (12 male, age range: 18–30 years, mean = 21.96, SD = 3.36) participated in the study. 9 mm2 circular sponge electrodes were placed over the bilateral IFG. In three separate sessions, 1 mA tACS at 10 Hz or 16.18 Hz or sham stimulation were applied for 20 min. Before and after stimulation, 5 min of resting state EEG was recorded. The phonological task required the subjects to indicate via button press whether highly frequent German nouns like ‘Zebra’ consisted of two or three syllables. In a simple control task, participants had to indicate whether an arrow pointed left or right to control for unspecific effects. Results: (1) Stimulation was a significant predictor for decision speed in the phonological task (p = .02). Specifically, participants responded faster after 10 Hz relative to sham stimulation, but not after 16.18 Hz. (2) This effect was task specific as tACS did not significantly affect the control task (p = 0.43). (3) Participants had an increase in resting state alpha power (p = .004), which wasn’t modulated by stimulation (p = .70). (4) We found a significant event related desynchronization in the alpha band (p < .001), which wasn’t modulated by stimulation (p = .79). Conclusion: The results show an improvement in a phonological word task after applying 10 Hz tACS over the bilateral IFG but not in simple motoric control task. This might be explained by a paradoxical facilitation effect, resulting in an ‘optimal’ level of noise for task processing (Miniussi et al., 2013) or by inhibition of surrounding areas that might be competing for task resources. Since no specific effect on alpha oscillations could be found, further studies will therefore investigate effects of focal online stimulation.

P111. Exploring the effects of transcranial direct current stimulation on cognitive control training—S. Weller *, C. Plewnia (Universitätsklinikum Tübingen, General Psychiatry and Psychotherapy, Polyclinic Neurophysiology, Neuropsychiatry, Tübingen, Germany) ⇑

Presenting author.

Introduction: The dorsolateral prefrontal cortex (dlPFC) is a brain structure responsible for working memory performance and cognitive control (CC). CC, critically underlying goal-directed behaviour, has been shown to be impaired in depression and to be associated with reduced activity of the dlPFC (Fitzgerald and Laird, 2008). Transcranial direct current stimulation (tDCS) of this brain area can modify the neuronal response and therefore CC, and has already shown potential for CC malleability: both amelioration as well as impairment (Wolkenstein and Plewnia, 2013; Plewnia et al., 2015a, Plewnia et al., 2015b). Within this study series we systematically investigate the effects of tDCS on a CC training in healthy participants by varying stimulation parameters regarding intensity, polarity and laterality. Methods: Over the course of 8 sessions within 4 weeks and a follow-up session 3 months later participants perform a modified adaptive paced auditory serial addition task (PASAT) during which they hear a series of single digit numbers and are instructed to add the most recent digit to the third to last digit (n + n 2). Digit presentation speed is adapted to performance with the goal to challenge CC by inducing stress and frustration during the experiment. TDCS is applied for 19 min during each training session. The first two test groups receive stimulation of the left dlPFC with 1 and 2 mA respectively, the third and fourth group are treated likewise except for stimulation being shifted to the right dlPFC. Each group is furthermore divided into subjects receiving either anodal, cathodal or sham tDCS. Preliminary results and conclusion: Within the first study group, subjects who received anodal stimulation (1 mA) to the left dlPFC showed significant performance gains during PASAT training compared to cathodal (1 mA) and sham stimulation, suggesting that improvement was aided by plasticity enhancement of CC induced by tDCS. Outlook: Data for the remaining three groups (2 mA, left dlPFC; 1 and 2 mA, right dlPFC) is currently being gathered. Collection will be finished by the end of the year, ensuing final analysis of the comprehensive data set by the beginning of 2018. References Fitzgerald P, Laird A. A meta-analytic study of changes in brain activation in depression. Hum Brain Mapp 2008;29(6):683–95. Plewnia C, Schroeder PA, Kunze R, Faehling F, Wolkenstein L. Keep calm and carry on:

Abstracts / Clinical Neurophysiology 129 (2018) e48–e116 improved frustration tolerance and processing speed by transcranial direct current stimulation (tDCS). PLoS One 2015a;10(4):1–12. Plewnia C, Schroeder PA, Wolkenstein L. Targeting the biased brain: noninvasive brain stimulation to ameliorate cognitive control. Lancet Psych 2015b;2(4):351–6. Wolkenstein L, Plewnia C. Amelioration of cognitive control in depression by transcranial direct current stimulation. Biological psychiatry, vol. 73. Elsevier; 2013. doi:10.1016/j.clinph.2018.04.728

P112. Modulatory effects of anodal transcranial direct current stimulation on fronto-striatal gain control of the interplay between selective attention and perception —K. Gohil 1,*, S. Passow 1, N. Adelhöfer 2, C. Beste 2, S.C. Li 1 (1 Technische Universität Dresden, Entwicklungspsychologie und Neurowissenschaft der Lebensspanne, Dresden, Germany, 2 Universitätsklinikum Carl Gustav Carus Dresden, Kinder und Jugendpsychiatrie und -psychotherapie, Dresden, Germany) ⇑

Presenting author.

Carrying conversations in public spaces with a plethora of competing sensory inputs demands flexible interactions between attention and perception for selectively processing goal-relevant information. We postulate that the fronto-striatal network plays a key role in regulating this interaction. However, to date the underlying gain control mechanisms are not yet well understood. Neuronal gain control can be fine-tuned by membrane potential regulated changes in neuronal excitability. Anodal transcranial current stimulation (atDCS) has been shown to cause a depolarization of resting membrane potentials, which increases neuronal excitability. In the present study, we applied off-line atDCS over the right inferior frontal gyrus (IFG) in healthy young adults in a single-blinded sham-controlled study to investigate atDCSinduced effects on fronto-striatal gain control of auditory attention. We recorded high-density EEG recordings during a dichotic listening task in which both perceptual saliency and attentional focus were varied, creating conditions of low and high perceptual-attentional conflict. Compared to sham stimulation, pilot results suggest that atDCS enhanced auditory perception and attentional regulation: Specifically, atDCS increased discrimination ability of inter-aural intensity differences and enhanced performance in high conflict conditions. These behavioral effects were reflected by EEG correlates associated with attentional and perceptual processing. doi:10.1016/j.clinph.2018.04.729

P113. Effects of theta-burst rTMS on cortical networks as probed with TMS-evoked potentials—S.M. Günther 1,*, C. Tscherpel 2,1, L. Hensel 1, C. Grefkes 2,1 (1 Universitätsklinikum Köln, Clinic and Polyclinic of Neurology, Köln, Germany , 2 Forschungszentrum Jülich, Institute for Neurosciences and Medicine (INM-3), Jülich, Germany) ⇑

Presenting author.

Background: Intermittent theta burst stimulation (iTBS) as a specific protocol of repetitive transcranial magnet stimulation (rTMS) has been shown to induce changes in cortical excitability that last

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beyond stimulation. However, effects are subject to a high degree of intra- and inter-individual variability (Hamada et al., 2013 Cereb Cortex; Diekhoff-Krebs et al., 2017 Neuroimage Clin.). Combining transcranial magnet stimulation (TMS) with electroencephalography (EEG) allows investigating cortical responses with high spatiotemporal specificity and sensitivity. Here, TMS-evoked potentials (TEPs) can be used to test the reactivity and connectivity of cortical areas and thereby to examine the direct effects of iTBS on the cortex. Therefore, the study aims at furthering our insights into the individual neural underpinnings underlying iTBS-induced changes of cortical excitability. Methods: A group of young (20–35 years), healthy subjects received three serially applied blocks of iTBS over the primary motor cortex (M1 stimulation) or over parieto-occipital vertex as control condition (Sham stimulation) in two stimulation sessions (washout period: at least 10 days). As behavioural parameters, motor performance was assessed using two different motor tasks, Purdue Pegboard Test (PPT) and maximum finger tapping. TMS-EEG was recorded online at baseline and after each application of iTBS using a TMS-compatible 64-channel EEG-System (BrainProducts). Neuronavigated TMS was applied as single pulses with 80% of resting motor threshold (RMT). Results (preliminary): iTBS over M1 increased MEP amplitudes compared with sham stimulation after each stimulation block. There was, however, considerable between-subject differences in the individual responses to iTBS. In addition, iTBS increased performance in the Purdue Pegboard Test but not in the maximum finger tapping task. At the neural level, we found differential changes in TEP components, with enhancement of the N100 component which is thought to reflect inhibitory mechanisms. Conclusion: This is the first study investigating network effects of iTBS by means of TMS-EEG. Our preliminary results suggest that iTBS causes effects at the behavioural and local level (cortical excitability) as well as affecting specific components of TMSevoked potentials. doi:10.1016/j.clinph.2018.04.730

P115. Painful mydriasis as the only clinical sign of an ipsilateral midbrain abscess—F. Thömke (Klinikum Worms, Department of Neurology, Worms, Germany) History: A 39-year-old man noted increasing right frontal and right retroorbital pain. After 3 days, he also noted blurred vison in the right eye. On clinical examination, he had a mydriatic right pupil with diminished light reaction but otherwise normal findings including eye movements examination (and direct-current electrooculography). Findings: Masseter reflex testing disclosed an increased latency on the right side and was interpreted in favor of an ipsilateral mesencephalic lesion. MRI documented an abscess in the left ventral midbrain involving the region of the distal intramesencephalic segment of the 3rd nerve. Cerebrospinal fluid analysis revealed 185 leucocytes/ll, mildly elevated total protein (536 g/l), and normal glucose and lactate levels. There was no serological evidence for neuroborreliosis, neurolues, brucellosis, leptospirosis, echinococcosis, or fungal infections. Transesophageal echocardiography and dental and otolaryngological examinations were normal. Treatment: He was treated with a combination of ceftriaxone (2  2 g/d) plus flucloxacillin (4  2 g/d) plus metronidazole