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Introduction Flexible goal-directed behaviour requires an adaptive cognitive control system for context-specific organization and optimization of information processing. Because the continuous monitoring of the outcome of ongoing actions as well as the subject’s motivation are essential for adaptive control over one’s own performance, neuronal mechanisms of post-error processing were investigated in the motivational context of trials with different incentive load. These mechanisms were characterized in terms of changes of post-error oscillatory processes in a Go-NoGo task performed in MEG scanner. Developmental influences on neuronal mechanisms of error monitoring in the context of motivation were studied in different age groups of healthy children and adolescents. Methods Fifteen healthy right-handed children aged 10–16 years participated as subjects. The Go-NoGo task was applied in two conditions: (A) standard Non-incentive Go-NoGo , and (B) rewarded Incentive Go- No-Go with two reward valences: reward for successful inhibition and response cost for error (for detailed description see Liddle et al., 2011; Mazaheri et al., 2009 ). The visual stimuli were single digits between 1 and 9 presented in the lower left visual field. Non-incentive Go-NoGo : each stimulus was displayed for 0.2 s and the inter-trial interval was 1.5 s. Participants were asked to respond to all digits except of “5” by pressing a button with the right index finger. Digits “1–4” and “6–9” are thus the Go stimuli and digit “5” the NoGo stimulus. Incentive Go-NoGo : the procedure was as in the non-incentive condition with a one difference: for each successful NoGo the subjects obtained a point, and for each false alarm they lost 5 points. The MEG data were acquired using a 275-channel whole-head MEG system (Omega 2005, CTF-MEG, VSM MedTech Inc., Coquitlam, Canada). Results In the non-incentive Go-NoGo condition, there was a significant increase of power in the theta frequency band in the dorsolateral and medial prefrontal cortex bilaterally immediately after an error and reduction of alpha power in the parietal cortex 200–800 ms after an error ( p < 0.001). In the incentive Go-NoGo condition, the changes after an error were similar and significant, but less pronounced. The direct comparison between conditions with and without incentive load revealed significant differences in the left parietal and central cortex for the alpha frequency band ( p = 0.028). In these regions, there was a reduction of alpha activity in the condition without motivation and an increase in the motivational context. The described changes were more pronounced in adolescents than in children. Conclusion The error monitoring and adaptive post-error optimization in children and adolescents is based on the neuronal signature related to the increase in activity in the prefrontal cortex and decrease in the regions of the default mode network. The increased motivation causes significant changes in pre-activation in the central motor region. The study illustrates neuronal mechanisms responsible to the improvement of performance in the motivation context. [ABSTRACT FROM AUTHOR]

Introduction. Non-invasive neuromodulation via transcranial direct current stimulation (tDCS) is a promising method for modulating plasticity. For the first time multichannel tDCS was used to investigate a larger number of children and young adolescents. Previous studies suggest that tDCS affects cognitive functions. It is assumed that the inferior frontal gyrus (IFG) has an important role in the process of response inhibition. Therefore, multichannel tDCS might has potential as therapy option for neurodevelopmental diseases such as attention deficit hyperactivity disorder (ADHD). The present study addressed the question whether tDCS could modulate this function. In addition, the study intended to investigate the most effective timing and tolerance of stimulation. Methods. The study was approved by the Ethic Committee of the Faculty of Medicine of Kiel university. 29 healthy participants (10-17 years old, mean age: 14,2 years, SD 2,14) were included in the analysis in a double-blinded and sham-controlled crossover study. The Flanker-task was used as target-task so that reaction time and accuracy were focused in the evaluation. Stimulation was scheduled prior (offline) or during (online) target task. After that the participants completed the n-back-task and the CPT-task as non-target-tasks. Resting state EEG was recorded before and after stimulation. Additionally, task related EEG was performed to expose changes at the neurophysiological level. For multichannel 2 mA tDCS over the right IFG we used a 6-channel solution (3.14 cm2 circular electrodes, positioned at F8 (1000 µA), FC6 (999 µA), P7 (−377 µA), T8 (−422 µA), C6 (−577 µA) and FPZ (−623 µA), filled with EEG electrode gel). Current was ramped up for 30 seconds at the beginning and the end in sham as well in verum stimulation. A linear mixed model was used for statistical evaluation. Results. There were only a few participants showing side effects such as itching, burning or fatigue. In a total of 112 sessions there were eight cases of adverse events such as headache. Our preliminary results at the behavioural level show no significant differences (p > 0.05) between tDCS and sham stimulation. There were no significant effects on accuracy or reaction time between online or offline stimulation neither. Conclusion. Our results show that tDCS was tolerated well by the participants. Based on preliminary results we could not confirm that tDCS could modulate the rIFG because response inhibition was not affected significantly. Further analysis could find out about possible reasons for our results such as ceiling effects. Analysis of resting EEG prior and after stimulation as well as task related EEG might yield neurophysiological explanation for the absence of behavioural improvement outcomes. The results provide a basis for future studies such as investigations of ADHD patients and might offer a compatible therapy option. [ABSTRACT FROM AUTHOR]

Introduction. Transcranial direct current stimulation (tDCS) is a non-invasive method of modulating brain activity. Previous studies with common tDCS montages have shown that there are positive effects on the left inferior dorsolateral prefrontal cortex (lDLPFC) for both healthy and clinical population like improvement of the working memory. Nevertheless, there is still lack of clear guidelines and safety instructions, probably due to not specific enough simulation montages, especially when focusing on pediatric population. This study aims to investigate behavioral outcome of multichannel tDCS over the lDLPFC in healthy children and adolescents. Therefore, tDCS was coupled with a memory task, especially focusing on accuracy and reaction time changes. Methods. The study was approved by the Ethic Committee of the Faculty of Medicine of Kiel University. The study was conducted in a double-blinded, randomized, sham-controlled design. 28 healthy children and adolescents (Age range: 10–17 years, mean age = 14,18, SD = 2,23) were included in the analysis. In four separate sessions, they received multichannel 2 mA anodal or sham tDCS for 20 minutes over the left DLPFC before or during working memory task (2 back task). At the behavioral level response time and accuracy for N-back task were evaluated. Additionally, safety and tolerability of multichannel tDCS has been investigated by written questionnaires. For multichannel 2 mA tDCS over DLPFC we used a 6-channel solution (3.14 cm2 circular electrodes; AF3 (897 μΑ), AF7 (284 μΑ), F3 (819 μΑ), Fp2 (−1000 μΑ) und T7 (−1000 μΑ)). Before, during and after stimulation 32 channel EEG was recorded in order to demonstrate neurophysiological changes. All materials required for the stimulations and EEG recording were obtained from Neuroelectrics (Barcelona, Spain). Results. All participants tolerated the stimulation well. Our preliminary behavioral results showed that there were no significant effects on accuracy (ACC) or reaction time (RT) compared tDCS to sham stimulation. There were also no significant effects on ACC and RT between online or offline stimulation and no significant effects in the interaction of these variables (p > 0.05). Conclusion. In summary, our study demonstrates that multichannel tDCS over DLPFC with 2 mA intensity over 20 min is well tolerated, and thus may be used as an experimental and treatment method in the pediatric population. Based on preliminary behavioral data, we could not show any stimulation effect. In accordance to literature though, stimulation often shows bigger effects on clinical population rather than healthy participants. Possible reasons for null findings could be ceiling effects (e.g. Suitability of the Paradigm depending on age). Furthermore, individual differences like baseline activity, may have had an impact on stimulation effectivity. Additional EEG analysis may provide more specific insights into developmental aspects of working memory processing on the neural level. [ABSTRACT FROM AUTHOR]

Introduction. Previous research revealed significant effects of tDCS (transcranial direct current stimulation) over the dorsolateral prefrontal (DLPFC) on cognition. However, the effects of right- vs left-sided stimulation on different cognitive domains has not been sufficiently studied. Therefore, this study aimed at showing differential effects of right- vs left-sided tDCS of the DLPFC on different cognitive domains depending on the stimulated hemisphere. Methods. Healthy participants aged 20 to 35 years were randomly assigned to one of three groups in a double-blinded randomized controlled trial. Participants underwent tDCS either of the left (N = 20) or the right hemisphere (N=20), or sham stimulation (N=20). A neuropsychological test battery comprising verbal as well as non-verbal tasks covering different cognitive domains was conducted on three consecutive days. Stimulation was scheduled prior to the cognitive assessment on the second day. For this, we used the 10-10 hybrid StarStim 32 EEG-tDCS system with a total inject stimulation current of 2 mA distributed over 5 electrodes (right group: AF4 0.976 mA, F4 0.976 mA as anodes and Fpz −0.731 mA, FC6 −0.730 mA, Cz −0.491 mA as cathodes; left group: AF3 0.999 mA, F3 1.0 mA as anodes and FC5 −0.848 mA, Fpz -.820 mA, Cz −0.331 mA as cathodes). The same system was used to derive an electro encephalogram (EEG) before and after stimulation. Performance directly and 24 hours after stimulation was compared to baseline with repeated measurement ANOVA. For two tests comprising several parameters (verbal memory test "VLMT" and test for attentional and executive functions "EpiTrack") repeated measurement MANOVA was performed. Results. No significant interactions were found, yet non-verbal working memory (block span) and variability in reaction time of a Go/NoGo paradigm showed a slight effect (p <.10): Left-sided anodal tDCS inhibited non-verbal working memory directly after stimulation. With anodal stimulation on either side, subjects appeared to benefit less from repetition effects in reducing variability in response times. Conclusion. While left-sided tDCS of the DLPFC slightly inhibited a spatial working memory task, our study found no further indications of cognitive effects specific to the side that was stimulated. Analysis of resting EEG prior and after stimulation might yield neurophysiological correlates for the observed behavior outcomes. [ABSTRACT FROM AUTHOR]

Introduction Recent studies show that tDCS applied over the left dorsolateral prefrontal cortex (lDLPFC) can successfully affect working memory (WM) performance ( Coffman et al., 2014 ). The present study investigates the influences of a classical bipolar and more focal multichannel tDCS over the lDLPFC on WM performance (2-back task) and continuous performance task (CPT) as non target task as well as on resting-state EEG oscillations and ERPs. Methods The study was approved by the Ethic Committee of the Faculty of Medicine Christian-Albrechts University Kiel. Eighteen healthy young adults (18–30 years) participated in the study. Participants were stimulated 3 times (bipolar, multichannel, sham stimulation in randomized order) over the lDLPFC for 20 min, minimum period between sessions was 7 days. For bipolar stimulation 1 mA was applied by two circular saline-soaked surface sponge electrodes (25 cm 2 ), with anode positioned over F3 and reference over FP2. For multichannel tDCS we used five 3.14 cm 2 circular PiStim electrodes (Neuroelectrics, Barcelona, Spain), positioned at AF3 (897 uA), AF7 (284 uA), F3 (819 uA), FP2 (−1000 uA) and T7 (−1000 uA). After stimulation EEG at rest (2 min eyes closed, 2 min eyes open) and during 2-back and CPT performance was recorded. Results Behavioral results show significant improvement of accuracy in the 2-back task after multichannel and bipolar tDCS compared to sham stimulation but not for CPT performance. Incidence and intensity of aversive side effects did not differ between multichannel, bipolar or sham tDCS. Conclusion Our results show that multichannel and bipolar tDCS over the lDLPFC have the potential of modulating WM performance, with multifocal stimulation not eliciting greater effects, which is in contrary to results of motor cortex area stimulation ( Fischer et al., 2017 ). Since WM performance but not non target-task performance was affected, our results suggest that the area of interest has been successfully stimulated. Our results on aversive side effect underline the tolerability of multichannel tDCS and bipolar tDCS. Additionally, participants were not able to discriminate real and sham stimulation effectively. However, future analyses, especially of obtained EEG data, will give further insight on the efficacy and tolerability of multichannel tDCS versus bipolar tDCS. This study was conducted as part of the STIPED program. STIPED has received funding from European Union’s Horizon2020 research and innovation programme under grant agreement No. 731827 . [ABSTRACT FROM 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 Hz-rTMS 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 mm 2 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. [ABSTRACT FROM AUTHOR]

Aim Applications of transcranial direct current stimulation (tDCS) aim at targeting specific cognitive domains. Optimization of tDCS protocols is therefore crucial. It has been suggested to combine tDCS with a cognitive task aiming at the networks related to the targeted cognitive domain. The present study investigates (1) the timing of tDCS in relation to the target task (working memory). (2) Specificity of DLPFC-stimulation on executive functions. Methods A total of 80 subjects aged 18–30 participated in the study; eight were excluded for IQ above 130 (40 female; age M  = 22.0, SD = 3.2; IQ M  = 107.2, SD = 11.1). Twenty-four hours after baseline examination (T0), participants were randomly allocated to one of four different conditions of tDCS timing: Verum stimulation (1) before, (2) during and (3) after performing an adaptive n-back task (T1) as well as (4) sham stimulation during the n-back task. 1.5 mA anodal tDCS was delivered through the Starstim system for 17 min (Neuroelectrics, Barcelona, Spain). The size of the circular active electrode (left DLPFC) was 8 cm 2 and of the reference electrode 25 cm 2 (contralateral mastoid). Cognitive examination covered attention, executive functions (working memory, cognitive flexibility, inhibitory control), verbal and non-verbal memory, and visuo-spatial functioning. Repeated measurement ANOVA was performed to compare each verum condition to sham stimulation. Results Concerning executive functions, participants in the conditions ‘before’ and ‘after’ didn’t improve as much as the sham group at T1 in a Go-NoGo task (median reaction time). Regarding memory, participants in the condition ‘before’ didn’t improve as much as the sham group at T1 in non-verbal delayed recall (Rey-Osterrieth Complex Figure Test). Participants in the ‘during’ condition improved at T1 compared to the sham group in verbal delayed recall (Rey Auditory Verbal Learning Test). Discussion These preliminary results show that anodal tDCS over the left DLPFC can selectively modulate single functions from executive functions and memory. (1) Stimulation before and after an executive target task showed similar negative effects on inhibitory control, while stimulation during the target task did not show any effect on executive functioning. Yet, we only saw changes in one out of seven conducted executive tasks. Therefore, we cannot conclude a preferred timing of stimulation in relation to a working memory task aiming at the networks of executive functions through DLPFC stimulation. Interestingly, the only positive effects on cognition were seen with stimulation during the target task. (2) Stimulation during the target task had a positive impact on delayed recall in verbal memory, which is known to be hippocampus-dependent. Together with the negative effect on non-verbal delayed recall in the ‘before’ condition, these results indicate a wider, impact of tDCS on cognition, possibly related to electrode montage and subsequently activated brain networks. [ABSTRACT FROM AUTHOR]

Introduction Previous studies suggested that acoustic stimulation can be used to modulate cognition, to reduce anxiety level as well as to enhance mood. In this study we investigated whether acoustic stimulation can modulate response inhibition and error monitoring in a continuous performance task. Using the Go-NoGo paradigm in healthy adults during MEG recordings, Mazaheri et al. (2009) was able to predict errors during response inhibition by theta-alpha coupling. Thus, it seems likely that frontal theta activity after an error may boost an adjustment of the mental state of individuals towards more preparatory alertness resulting in alpha decrease and better sustained performance. Here, we investigated whether acoustic stimulation can modulate theta-alpha-coupling and thereby have an effect on error processing. Methods 20 healthy young adults (18–30 years) participated in the crossover study. They ran through four conditions (randomized order): no stimulation, white noise, binaural beats at a frequency of 6 Hz and monaural beats at a frequency of 6 Hz. For all time points first, an EEG recording at rest with eyes closed (“Resting state”-EEG, 5 min) with stimulation (at 3 conditions) was performed. This is followed by an acoustic stimulation simultaneously with the implementation of an inhibition task (Go-NoGo task). Go/NoGo task: Each stimulus (numbers 1–9) was displayed for 0.2 s and the inter-trial interval was 1.5 s. Participants were asked to respond to all digits except of “5” by pressing a button with the right index finger. Digits “1–4” and “6–9” are thus the Go stimuli and digit “5” the NoGo stimulus. Correct Go-trials were categorized as “hits”, correct No-Go-trials as “withholds”, and responses on No-Go as “false alarms”. Stimulation: Acoustic stimulation was performed in different ways. Binaural beats were generated by presenting one ear with a different tone than the other ear. The difference in frequencies, in our case 6 Hz, results in a beating sensation. Whereas the prior superimposition of two tones with different frequencies result in a monaural beat, again at 6 Hz, that is then presented to the subject. Additionally we use white noise and no noise as a control condition. Results Preliminary behavioral results show a tendency towards improvement of the number of false alarms during the three noise conditions. However, there are no significant findings. Looking at reaction times in false alarms, stimulation conditions have longer reaction times than no stimulation. Especially white noise shows longer reaction times while having the lowest variability in reaction times. Additionally the monaural beat stands out with a very high variability in reaction times. Conclusion Our behavioral results so far show that acoustic stimulation could have the potential of modulating behavioral responses. So far, white noise seems to be a stimulation that might be able to stabilize performance variability in subjects. As a next step EEG-data as correlates of the behavioral data will be analyzed. These results shall be the basis for further studies, for example, with ADHD subjects. [ABSTRACT FROM AUTHOR]

Introduction Tranccranial random noise stimulation (tRNS) induces a consistent excitability increase lasting at least 60 min after 10 min of stimulation, as demonstrated by both physiological measures and behavioural Tasks ( Terney et al., 2008 ). The present study tests whether the tRNS-induced changes in corticospinal excitability varies as a function of individual differences in sensitivity to sham stimulation. Methods The study was approved by the Ethic Committee of the Faculty of Medicine Christian-Albrechts University Kiel. 24 participants, aged between 18 and 30 years, participated in the study. All subjects were right-handed according to the Edinburgh handedness inventory ( Oldfield, 1971 ). Stimulation techniques : tRNS (1 mA, 10 min) was applied through a pair of saline-soaked surface sponge electrodes (5 × 7 cm). The minimum period between sessions for a single subject was 7 days, and sessions were applied in randomized order. Monitoring of motor cortical excitability: To examine changes in corticospinal excitability, motor evoked potentials (MEPs) of the right first dorsal interosseous muscle (FDI) were recording following stimulation of its motor-cortical representation field by single-pulse TMS. For further analysis we divided three subgroups according to excitatory (‘Excitatory group’, n = 9), inhibitory (‘Inhibitory group’, n = 7) or no respond (‘Non responder group’, n = 8) to sham- stimulation (Wilcoxon signed-rank test for dependent sampling). For this, we compared the MEP-amplitude in mean of the three time points after stimulation with the MEP-amplitude in mean before. Results In all subjects the tRNS was well tolerated. The general finding of present study is that sensitivity to sham stimulation has impact on effect of tRNS; namely, ‘Excitatory group’ resulted in inhibition of tRNS, whereas inhibitory group shows excitation of tRNS. For ‘Non responder group’ the 1 mA tRNS resulted in a significant increase of MEP amplitudes compared to sham stimulation, which is consistent with the literature Conclusion Accounting for variation in individual sensitivity to sham stimulation, stimulation may influence the utility of tRNS as a tool for understanding brain-behavior interactions and as a method for clinical interventions. [ABSTRACT FROM AUTHOR]

Introduction Response inhibition, as a hallmark of executive control, refers to the suppression of actions that are no longer required or that are inappropriate, which supports flexible and goal-directed behaviour in ever-changing environments. In this study, we intend to prove whether the boosting of theta activity by electrical stimulation in the prefrontal cortex (pre-SMA & IFC) would (1) increase theta power in prefrontal cortex; reduce alpha power in OPC; (2) reduce number of errors in a continuous performance task; (3) to see whether pre-SMA or IFG is the important structure for motor response inhibition and process monitoring. Methods The studies were approved by the Ethic Committee of the Faculty of Medicine Christian-Albrechts University Kiel. Stimulation Transcranial alternating current stimulation (tACS) was delivering by a battery driven stimulator (NeuroConn GmbH, Ilmenau, Germany) through conductive-rubber electrodes (9 cm 2 ). So far, 12 subjects participated in four different experimental studies and they received on separate days tACS at three frequencies (6 Hz over preSMA and over rIFG, 20 Hz (frequency of no interest) over rIFG and sham stimulation. The minimum period between sessions for a single subject was 7 days. To stimulate pre-SMA: 4 cm anterior to Cz ( matches Fz) and reference electrode over contralateral supraorbital area ; to stimulate IFG: crossing point between T8-Fz and AF8-Cz. Go/NoGo task each stimulus was displayed for 0.2 s and the inter-trial interval was 1.5 s. Participants were asked to respond to all digits except of “5” by pressing a button with the right index finger. Digits “1–4” and “6-9” are thus the Go stimuli and digit “5” the NoGo stimulus. Correct Go-trials were categorized as “hits”, correct No-Go-trials as “withholds”, and responses on No-Go as “false alarms”. Results Preliminary results with 14 subjects in each condition indicate that there’s a significant difference in reaction times between hits and false alarms (in all conditions), which is consistent with the literature. Regarding the differences between conditions, there are no significant statistical differences as of now, but this might be due to the small number of subjects in each condition. There seem to be slight trends for 6Hz pSMA compared to sham: Mean reaction times for hits and false alarms were highest for 6 Hz stimulation at the pSMA. Regarding the ratio of hits and false alarms (actual number divided by potential number), subjects had the highest ratio of hits in sham stimulation and the lowest ratio in 6 Hz stimulation of pSMA. The pattern for false alarms is similar: subjects had the lowest ratio of FAs in 6 Hz stimulation of pSMA with all other conditions appearing mostly equal. Conclusion Our behavioral results so far showed that tACS could have potential in modulating behavioral responses, however future studies could improve on this study by analyzing EEG-data as correlates of the behavioral data and having larger sample sizes. [ABSTRACT FROM AUTHOR]