- Email: [email protected]
Brain stimulation, aging and cognition
428
Abstracts / Brain Stimulation 10 (2017) 346e540
impact of the lesion site and size, and to identify whether the tDCS target region was intact, structural MRI data were obtained during the pretreatment scanning session. To establish whether tDCS supports re-recruitment of LH structures, lateralisation indices (LI) will be calculated as a measure for the relative contribution of the left and right hemisphere. LIs will be compared for patients receiving tDCS versus patients receiving sham, both pre and post treatment. We will unveil the significantly activated brain areas during both paradigms, in relation to behavioural performance on these language tasks. Results: At present, the analysis is ongoing. Results will be available in March 2017. Discussion: The results of this study will improve our understanding of tDCS-induced language reorganisation, and will contribute to the ongoing discussion among aphasiologists on the roles of the RH and LH in poststroke language reorganisation. Keywords: transcranial Direct Current Stimulation, neural reorganisation, aphasia, stroke [0386] A SIMPLE SIMULATION MODEL FOR SPIRAL INDUCED EPILEPSY A. Rabinovitch*2, Y. Biton 2, M. Friedmabn 3, I. Aviram 2, D. Braunstein 1. 1 Sami Shamoon College of Engineering, Israel; 2 Ben-Gurion University of the Negev, Israel; 3 Ben-Gurion University, Israel In order to effectively use DBS for epileptic seizures the electrodes location is crucial and depends on the understanding of the phenomenon. We assume that epilepsy in the brain is a similar phenomenon to that of heart fibrillation. Since the phenomenon of heart fibrillation, both in the atria and in the ventricles, is known to be initiated by a spiral (rotor), the assumption entails a spiral source also for epilepsy. Effective DBS should then be targeted to eliminate a developing ominous spiral wave In order to investigate this hypothesis, we wanted to use a simple numerical model. Existing models of nervous brain operation are rather complicated. We therefore adapted for this task a model which is relatively very simple but is versatile enough to enable spatiotemporal responses and E.E.G.’s similar to the actual ones. The model is based on the MorrisLecar system of equations with diffusion. Temporal changes of “external current” and the diffusion constant are used to simulate alterations of excitation-inhibition neuron dominance. The model is used to investigate brain response to an initial spiral wave. It is shown that, indeed, this procedure can lead to epileptic-like patterns: Starting with a spiral in a self-contained excitatory medium, the model uses different random changes of the connectivity and of the excitability level, simulating actual brain conditions. Results demonstrate that in some cases the initial spiral breaks down into many repeating patterns, ectopic sources and double spirals, similar to fibrillatory patterns in the heart. Simulated EEG’s are calculated by restrained averaging of local action potentials. Those reveal “disordered” behavior ordinary in epilepsy. E.E.G. spikes appearing in epilepsy could be the result of the initial spiral itself. Keywords: epilepsy, rotor, spiral, Morris-lecar [0387] STIMULATING YOUNG MINDS: INVESTIGATING A NEXT GENERATION TREATMENT FOR DEPRESSION IN YOUTH M. Kaur*1, 2, D.F. Hermens 2, R.S.C. Lee 2, J. Lagopoulos 2, 3, S.L. Naismith 2, 4, P.B. Fitzgerald 1, E.M. Scott 2, 5, I.B. Hickie 2. 1 Monash Alfred Psychiatry research centre, Australia; 2 University of Sydney, Australia; 3 University of the Sunshine Coast, Australia; 4 University of Sydney, Australia; 5 Young Adult Mental Health Service, Australia Background: One third of young patients with depression do not respond to antidepressants and are at risk for chronic treatment resistance. Repetitive transcranial magnetic stimulation (rTMS) has shown to be efficacious in treating depression, however, few studies have investigated patients at earlier stages of illness when providing optimal treatments are likely to result in better response outcomes. A subset of patients show inadequate response to rTMS and identifying features of patients that predict response is needed to inform personalised approaches. Methods: In this open-label study, 17 young inpatients and outpatients with depression (aged 18-30; 22±3.8) were recruited. Neuronavigationally
targeted high frequency (10 Hz) rTMS was administered at 110% of resting motor threshold on the left DLPFC for 45 trains of 4 seconds for 20 sessions over 4 weeks. Clinical interview, cognitive assessment and, psychosocial self-report scales were carried out within 2 weeks pre- and post-treatment. Results: Paired-samples t-tests revealed that depression, anxiety and psychiatric symptoms were significantly reduced with rTMS treatment (all p<.05) but no significant changes in cognitive or psychosocial functioning were found (p>.05). Greater improvements in depressive symptoms were associated with better pre-treatment set-shifting performance (p<.05; r¼.53). In patients with moderate-severe depression (n¼9), greater improvements in psychiatric symptoms were associated with later age of illness onset (p<.05; r¼.88). Conclusion: In keeping with the literature, rTMS improves depressive, anxiety and psychiatric symptoms in young people. These data suggest that cognition may have utility in predicting rTMS treatment response and targeting rTMS earlier in the course of illness may result in better response outcomes in young people with depression. Keywords: repetitive transcranial magnetic stimulation, depression, youth, cognition [0388] RESPONSE TO HIGH-FREQUENCY REPETITIVE TRANSCRANIAL MAGNETIC STIMULATION OVER LEFT DORSOLATERAL PREFRONTAL CORTEX IS UNAFFECTED BY NUMBER OF TREATMENT SESSIONS IN MAJOR DEPRESSION: A SYSTEMATIC META-ANALYSIS OF RANDOMIZED, SHAM-CONTROLLED TRIALS C. Deblieck*2, M. Wampers 1, 2, P. Sienaert 1, 2, C. Bervoets 1, 2. 1 KU Leuven, Belgium; 2 UPC KU Leuven Z.org, Belgium Background: High frequency repetitive transcranial magnetic stimulation (HF-rTMS) of the dorsolateral prefrontal cortex (DLPFC) appears to have acute antidepressant properties. Studies have suggested that a higher number of sessions increases response rate: patients with major depression (MD) have achieved clinical response criteria between the 13th and 15th sessions and even after 5 weeks. The aim of this meta-analysis was to determine if number of sessions is related to the antidepressant effects of HF-rTMS. Method: Following a systematic literature search of Pubmed/Medline and PsycInfo, randomized, sham-controlled trials from 1999 to 2016 comparing the response % in patients with MD were included. The odds ratio (OR) was used as effect size measure to evaluate the effectiveness of TMS vs. sham. In case of heterogeneity in effect sizes, number of sessions as well as other variables (number of trains and pulses, frequency, intertrain interval) were evaluated. Results: The search resulted in 57 publications, totaling 1447 patients receiving real TMS and 1299 sham TMS. The response rate of > 40% improvement in the TMS condition was significantly higher than in the sham condition (OR ¼ 3.54; 95% Confidence interval: 2.66 e 4.69, p ¼ 0.000). Heterogeneity between studies was high (Q ¼ 79.88, p ¼ 0.020). Only number of trains influenced the OR, i.e., an increase in number of trains was associated with a decrease in the odds of response in the TMS vs. sham condition (b¼ 0.02, z ¼ -3.66, p ¼ 0.0003). Number of sessions did not influence the odds of response in the TMS vs. sham condition (b¼ 0.03, z ¼ 1.07, p ¼ 0.28). Conclusions: This review suggests that the TMS effect is uninfluenced by the number of sessions. Alternatively, it seems to be negatively correlated with the number of trains. More studies submitting patients to > 20 sessions are needed. Keywords: Response rate, major depression, meta-analysis, repetitive transcranial magnetic stimulation [0389] BRAIN STIMULATION, AGING AND COGNITION M.R.L. Emonson*1, 2, P.B. Fitzgerald 1, 2, N.C. Rogasch 2, K.E. Hoy 1, 2. 1 Monash University, Australia; 2 Alfred Hospital, Australia Introduction: Alterations in neural plasticity are reported to occur both across the lifespan and in Mild Cognitive Impairment (MCI). As MCI may represent a prodromal stage of neurodegeneration, it is important to further investigate these neural changes in order to inform the development of therapeutic interventions. One novel method to achieve this is by combining transcranial magnetic stimulation with
electroencephalography (TMS-EEG), which can provide information on local and global functional reactivity. The current study used TMS-EEG to characterise the differences in neural plasticity responses, and its relation to cognitive performance in younger, older and MCI participants. Methods: 20 healthy younger adults, 20 healthy older adults and 9 individuals with MCI participated in the study. All completed a neuropsychological battery, computerised cognitive tasks (n-back and Cogstate subtests) and TMSEEG (50 single pulses, 110%RMT, 0.2HZ + 5% jitter), prior to delivery of transcranial direct current stimulation (tDCS). 20 minutes 1mA tDCS was administered to the left dorsolateral prefrontal cortex (DLPFC), with TMS-EEG and cognitive tasks repeated across multiple time-points post-tDCS. Results: Preliminary analyses show a significant effect of time for TMSEvoked Potentials (TEPs) in the N120 amplitude in the left frontal region (p<.01). Post-hoc analysis revealed a reduction in the T20 compared to Pre and T5 time points (ps <.05) in younger and older adults. Behavioural measures showed n-back performance improved over time. In older adults, the N120 amplitude at T20 positively correlated with reaction time on the n-back task post-tDCS (p<.05). Discussion: Novel brain stimulation methods were used to characterise neurophysiological changes in aging and MCI. Preliminary results revealed reduction in N120, a marker of inhibition, post-tDCS in younger and older, but not MCI. Older adults who showed greater inhibition demonstrated faster reaction times on a working memory task. This suggests varied response and outcome to brain stimulation across the lifespan. Keywords: TMS-EEG, Transcranial Direct Current Stimulation (tDCS), Cognitive Aging, Mild Cognitive Impairment (MCI)
[0390] EFFECT OF SINGLE-SESSION TDCS ON COGNITION IN SCHIZOPHRENIA: A RANDOMIZED DOUBLE-BLIND CROSS-OVER STUDY V.S. Sreeraj*, A. Bose, H. Chabbra, V. Shivakumar, S.M. Agarwal, C.N. Janardhanan, N.P. Rao, K. Muralidharan, S. Varambally, G. Venkatasubramanian. NIMHANS, India Introduction: Cognitive impairment is an integral feature of schizophrenia and a major predictor of functional outcome. Combining cognitive retraining with transcranial direct current stimulation (tDCS) has been postulated to address these deficits. The effect of combining a neuropsychological/psychophysiological task with tDCS, called “online-tDCS” for cognitive enhancement in schizophrenia has not been rigorously evaluated yet. This proof-of-concept study aimed at evaluating the effect of a single session of “online-tDCS” on working-memory (WM) and other cognitive functions. Methods: The effect of 20 minutes anodal stimulation of left dorsolateral prefrontal cortex and cathodal stimulation of left temporoparietal junction during Sternberg’s task (a WM task) on the accuracies and reaction times of nBack test (measuring WM), digit symbol substitution test(DSST) (assessing attention and processing speed) and emotional matching and labeling test(EMALT) (evaluating social/emotional cognition) were measured. Among the 23 schizophrenia patients with cognitive deficits, 19 completed the study; 9 patients were randomized to receive online-tDCS sessions and 10 to offline-tDCS sessions. All patients received one session each of true and sham tDCS, 2-7days apart in a randomized counterbalanced double-blind cross-over design. Results: Repeated measures ANOVA revealed a significant interaction effect between type of tDCS (Online vs Offline) and trueness of tDCS (true vs sham), such that the reaction time of nBack tests (0,1&2-Back) improved in offlinetrue and online-sham tDCS session only (F¼6.12,p<0.05) (F¼5.01,p<0.05) (F¼5.48,p<0.05). No significant changes were noted in DSST and E-MALT. Discussion: Better performance after offline-true tDCS session as well as online-sham tDCS session meant both tDCS and sternberg’s task influenced in enhancing the WM performance across the session. Paradoxical failure of online-tDCS to enhance WM performance may be related to the aberrant plasticity in Schizophrenia which might attain a transitional ceiling on combining the two plasticity modulators. The transferability of improvement to other cognitive domains could not be appreciated. Keywords: Online-tDCS, Cognitive deficits, Schizophrenia, Working memory
[0391] PHASE OF BRAIN OSCILLATIONS DETERMINES THE DIRECTION OF INDUCED PLASTICITY IN REAL-TIME EEG-TRIGGERED TMS C. Zrenner*, P. Belardinelli, D. Desideri, U. Ziemann. University of Tübingen, Germany Introduction: Can the large intra- and inter-individual variability of the effects induced by different repetitive TMS protocols be explained by the dynamics of ongoing activity at the time of stimulation? This study examined the influence of endogenous sensorimotor 10 Hz alpha rhythm on corticospinal plasticity Methods: A custom-built millisecond-accuracy real-time signal processing system was used to trigger repetitive TMS bursts according to the instantaneous phase of sensorimotor rhythm. Each burst was triggered either during the EEG surface positive peak or the surface negative peak of the local mu-rhythm. Single TMS pulses were applied before and after the intervention to assess the plasticity effect on corticospinal excitability. Results: A sequence of 200 repetitive TMS bursts (triple pulses of 100 Hz) delivered over a period of ca. 200 seconds resulted in a long-term (>30 min) increase of corticospinal excitability if triggered consistently at the EEG surface negative peaks of the mu-alpha oscillation, whereas the same TMS bursts triggered at the positive peaks decreased corticospinal excitability. Discussion: TMS triggered by a specific phase of an endogenous oscillation is a suitable tool to study the spatiotemporal properties of cortical dynamics and to induce reliable neuromodulatory effects in the human brain. In light of the results of this study, a realisation of the full therapeutic potential of brain stimulation in the treatment of brain network disorders will require a closed-loop approach that synchronises each stimulus with the individual patient’s instantaneous brain state. Keywords: real-time, closed-loop, neuromodulation [0394] MODULATION OF PHYSIOLOGIC ARTIFACTS DURING CONCURRENT TDCS AND EEG N. Gebodh*1, D. Adair 2, K. Chelette 3, Z. Esmaeilpour 1, 4, M. Bikson 1, J. Dmochowski 1, L.C. Parra 1, A.J. Woods 5, E. Kappenman 6. 1 The City College of New York, USA; 2 The Graduate Center at City University of New York, USA; 3 ANT Neuro North America, USA; 4 Amirkabir University of Technology, Iran; 5 University of Florida, USA; 6 University of California, USA Introduction: The field of non-invasive brain stimulation (NIBS) has benefited from integration with imaging including magnetic resonance imaging (MRI) and electroencephalography (EEG). Several studies have reported on concurrent tDCS and EEG, and used signal processing of varying complexity (e.g. high-pass filtering to ICA) to remove “non-physiologic stimulation artifacts” - namely artifacts arising from non-ideal stimulation and recording amplifier performance. None has compressively addressed “physiologic artifacts” which are defined here as non-stationary changes in artifacts resulting from interactions between the stimulation induced voltage and body. We identified and systematically characterized a series of tDCSinduced physiologic and nonphysiologic artifacts during concurrent EEG and High Definition (HD)-tDCS with physiological monitoring, and adapted MRIderived computational modeling to corroborate physiologic EEG findings. Methods: Subjects underwent three main simulation routines including 1) repeated, randomized, brief stimulation intensities over varied montages; 2) single intensity, randomized stimulation devices over a single montage; and 3) single device stimulation over a long duration with varied montages. Dosages ranged from 0.5-2.0 mA over 0.5-10 mins. Results: We identify and characterize three classes of artifacts including inherent stimulator artifacts, inherent physiologic artifacts, and noninherent artifacts. Physiologic artifacts included 1) cardiac distortion; 2) ocular motor distortion; 3) movement (myogenic) distortion. The power and voltage distribution of these artifacts were modulated in a tDCS montage, intensity, and polarity specific manner.
Abstracts / Brain Stimulation 10 (2017) 346e540
impact of the lesion site and size, and to identify whether the tDCS target region was intact, structural MRI data were obtained during the pretreatment scanning session. To establish whether tDCS supports re-recruitment of LH structures, lateralisation indices (LI) will be calculated as a measure for the relative contribution of the left and right hemisphere. LIs will be compared for patients receiving tDCS versus patients receiving sham, both pre and post treatment. We will unveil the significantly activated brain areas during both paradigms, in relation to behavioural performance on these language tasks. Results: At present, the analysis is ongoing. Results will be available in March 2017. Discussion: The results of this study will improve our understanding of tDCS-induced language reorganisation, and will contribute to the ongoing discussion among aphasiologists on the roles of the RH and LH in poststroke language reorganisation. Keywords: transcranial Direct Current Stimulation, neural reorganisation, aphasia, stroke [0386] A SIMPLE SIMULATION MODEL FOR SPIRAL INDUCED EPILEPSY A. Rabinovitch*2, Y. Biton 2, M. Friedmabn 3, I. Aviram 2, D. Braunstein 1. 1 Sami Shamoon College of Engineering, Israel; 2 Ben-Gurion University of the Negev, Israel; 3 Ben-Gurion University, Israel In order to effectively use DBS for epileptic seizures the electrodes location is crucial and depends on the understanding of the phenomenon. We assume that epilepsy in the brain is a similar phenomenon to that of heart fibrillation. Since the phenomenon of heart fibrillation, both in the atria and in the ventricles, is known to be initiated by a spiral (rotor), the assumption entails a spiral source also for epilepsy. Effective DBS should then be targeted to eliminate a developing ominous spiral wave In order to investigate this hypothesis, we wanted to use a simple numerical model. Existing models of nervous brain operation are rather complicated. We therefore adapted for this task a model which is relatively very simple but is versatile enough to enable spatiotemporal responses and E.E.G.’s similar to the actual ones. The model is based on the MorrisLecar system of equations with diffusion. Temporal changes of “external current” and the diffusion constant are used to simulate alterations of excitation-inhibition neuron dominance. The model is used to investigate brain response to an initial spiral wave. It is shown that, indeed, this procedure can lead to epileptic-like patterns: Starting with a spiral in a self-contained excitatory medium, the model uses different random changes of the connectivity and of the excitability level, simulating actual brain conditions. Results demonstrate that in some cases the initial spiral breaks down into many repeating patterns, ectopic sources and double spirals, similar to fibrillatory patterns in the heart. Simulated EEG’s are calculated by restrained averaging of local action potentials. Those reveal “disordered” behavior ordinary in epilepsy. E.E.G. spikes appearing in epilepsy could be the result of the initial spiral itself. Keywords: epilepsy, rotor, spiral, Morris-lecar [0387] STIMULATING YOUNG MINDS: INVESTIGATING A NEXT GENERATION TREATMENT FOR DEPRESSION IN YOUTH M. Kaur*1, 2, D.F. Hermens 2, R.S.C. Lee 2, J. Lagopoulos 2, 3, S.L. Naismith 2, 4, P.B. Fitzgerald 1, E.M. Scott 2, 5, I.B. Hickie 2. 1 Monash Alfred Psychiatry research centre, Australia; 2 University of Sydney, Australia; 3 University of the Sunshine Coast, Australia; 4 University of Sydney, Australia; 5 Young Adult Mental Health Service, Australia Background: One third of young patients with depression do not respond to antidepressants and are at risk for chronic treatment resistance. Repetitive transcranial magnetic stimulation (rTMS) has shown to be efficacious in treating depression, however, few studies have investigated patients at earlier stages of illness when providing optimal treatments are likely to result in better response outcomes. A subset of patients show inadequate response to rTMS and identifying features of patients that predict response is needed to inform personalised approaches. Methods: In this open-label study, 17 young inpatients and outpatients with depression (aged 18-30; 22±3.8) were recruited. Neuronavigationally
targeted high frequency (10 Hz) rTMS was administered at 110% of resting motor threshold on the left DLPFC for 45 trains of 4 seconds for 20 sessions over 4 weeks. Clinical interview, cognitive assessment and, psychosocial self-report scales were carried out within 2 weeks pre- and post-treatment. Results: Paired-samples t-tests revealed that depression, anxiety and psychiatric symptoms were significantly reduced with rTMS treatment (all p<.05) but no significant changes in cognitive or psychosocial functioning were found (p>.05). Greater improvements in depressive symptoms were associated with better pre-treatment set-shifting performance (p<.05; r¼.53). In patients with moderate-severe depression (n¼9), greater improvements in psychiatric symptoms were associated with later age of illness onset (p<.05; r¼.88). Conclusion: In keeping with the literature, rTMS improves depressive, anxiety and psychiatric symptoms in young people. These data suggest that cognition may have utility in predicting rTMS treatment response and targeting rTMS earlier in the course of illness may result in better response outcomes in young people with depression. Keywords: repetitive transcranial magnetic stimulation, depression, youth, cognition [0388] RESPONSE TO HIGH-FREQUENCY REPETITIVE TRANSCRANIAL MAGNETIC STIMULATION OVER LEFT DORSOLATERAL PREFRONTAL CORTEX IS UNAFFECTED BY NUMBER OF TREATMENT SESSIONS IN MAJOR DEPRESSION: A SYSTEMATIC META-ANALYSIS OF RANDOMIZED, SHAM-CONTROLLED TRIALS C. Deblieck*2, M. Wampers 1, 2, P. Sienaert 1, 2, C. Bervoets 1, 2. 1 KU Leuven, Belgium; 2 UPC KU Leuven Z.org, Belgium Background: High frequency repetitive transcranial magnetic stimulation (HF-rTMS) of the dorsolateral prefrontal cortex (DLPFC) appears to have acute antidepressant properties. Studies have suggested that a higher number of sessions increases response rate: patients with major depression (MD) have achieved clinical response criteria between the 13th and 15th sessions and even after 5 weeks. The aim of this meta-analysis was to determine if number of sessions is related to the antidepressant effects of HF-rTMS. Method: Following a systematic literature search of Pubmed/Medline and PsycInfo, randomized, sham-controlled trials from 1999 to 2016 comparing the response % in patients with MD were included. The odds ratio (OR) was used as effect size measure to evaluate the effectiveness of TMS vs. sham. In case of heterogeneity in effect sizes, number of sessions as well as other variables (number of trains and pulses, frequency, intertrain interval) were evaluated. Results: The search resulted in 57 publications, totaling 1447 patients receiving real TMS and 1299 sham TMS. The response rate of > 40% improvement in the TMS condition was significantly higher than in the sham condition (OR ¼ 3.54; 95% Confidence interval: 2.66 e 4.69, p ¼ 0.000). Heterogeneity between studies was high (Q ¼ 79.88, p ¼ 0.020). Only number of trains influenced the OR, i.e., an increase in number of trains was associated with a decrease in the odds of response in the TMS vs. sham condition (b¼ 0.02, z ¼ -3.66, p ¼ 0.0003). Number of sessions did not influence the odds of response in the TMS vs. sham condition (b¼ 0.03, z ¼ 1.07, p ¼ 0.28). Conclusions: This review suggests that the TMS effect is uninfluenced by the number of sessions. Alternatively, it seems to be negatively correlated with the number of trains. More studies submitting patients to > 20 sessions are needed. Keywords: Response rate, major depression, meta-analysis, repetitive transcranial magnetic stimulation [0389] BRAIN STIMULATION, AGING AND COGNITION M.R.L. Emonson*1, 2, P.B. Fitzgerald 1, 2, N.C. Rogasch 2, K.E. Hoy 1, 2. 1 Monash University, Australia; 2 Alfred Hospital, Australia Introduction: Alterations in neural plasticity are reported to occur both across the lifespan and in Mild Cognitive Impairment (MCI). As MCI may represent a prodromal stage of neurodegeneration, it is important to further investigate these neural changes in order to inform the development of therapeutic interventions. One novel method to achieve this is by combining transcranial magnetic stimulation with
electroencephalography (TMS-EEG), which can provide information on local and global functional reactivity. The current study used TMS-EEG to characterise the differences in neural plasticity responses, and its relation to cognitive performance in younger, older and MCI participants. Methods: 20 healthy younger adults, 20 healthy older adults and 9 individuals with MCI participated in the study. All completed a neuropsychological battery, computerised cognitive tasks (n-back and Cogstate subtests) and TMSEEG (50 single pulses, 110%RMT, 0.2HZ + 5% jitter), prior to delivery of transcranial direct current stimulation (tDCS). 20 minutes 1mA tDCS was administered to the left dorsolateral prefrontal cortex (DLPFC), with TMS-EEG and cognitive tasks repeated across multiple time-points post-tDCS. Results: Preliminary analyses show a significant effect of time for TMSEvoked Potentials (TEPs) in the N120 amplitude in the left frontal region (p<.01). Post-hoc analysis revealed a reduction in the T20 compared to Pre and T5 time points (ps <.05) in younger and older adults. Behavioural measures showed n-back performance improved over time. In older adults, the N120 amplitude at T20 positively correlated with reaction time on the n-back task post-tDCS (p<.05). Discussion: Novel brain stimulation methods were used to characterise neurophysiological changes in aging and MCI. Preliminary results revealed reduction in N120, a marker of inhibition, post-tDCS in younger and older, but not MCI. Older adults who showed greater inhibition demonstrated faster reaction times on a working memory task. This suggests varied response and outcome to brain stimulation across the lifespan. Keywords: TMS-EEG, Transcranial Direct Current Stimulation (tDCS), Cognitive Aging, Mild Cognitive Impairment (MCI)
[0390] EFFECT OF SINGLE-SESSION TDCS ON COGNITION IN SCHIZOPHRENIA: A RANDOMIZED DOUBLE-BLIND CROSS-OVER STUDY V.S. Sreeraj*, A. Bose, H. Chabbra, V. Shivakumar, S.M. Agarwal, C.N. Janardhanan, N.P. Rao, K. Muralidharan, S. Varambally, G. Venkatasubramanian. NIMHANS, India Introduction: Cognitive impairment is an integral feature of schizophrenia and a major predictor of functional outcome. Combining cognitive retraining with transcranial direct current stimulation (tDCS) has been postulated to address these deficits. The effect of combining a neuropsychological/psychophysiological task with tDCS, called “online-tDCS” for cognitive enhancement in schizophrenia has not been rigorously evaluated yet. This proof-of-concept study aimed at evaluating the effect of a single session of “online-tDCS” on working-memory (WM) and other cognitive functions. Methods: The effect of 20 minutes anodal stimulation of left dorsolateral prefrontal cortex and cathodal stimulation of left temporoparietal junction during Sternberg’s task (a WM task) on the accuracies and reaction times of nBack test (measuring WM), digit symbol substitution test(DSST) (assessing attention and processing speed) and emotional matching and labeling test(EMALT) (evaluating social/emotional cognition) were measured. Among the 23 schizophrenia patients with cognitive deficits, 19 completed the study; 9 patients were randomized to receive online-tDCS sessions and 10 to offline-tDCS sessions. All patients received one session each of true and sham tDCS, 2-7days apart in a randomized counterbalanced double-blind cross-over design. Results: Repeated measures ANOVA revealed a significant interaction effect between type of tDCS (Online vs Offline) and trueness of tDCS (true vs sham), such that the reaction time of nBack tests (0,1&2-Back) improved in offlinetrue and online-sham tDCS session only (F¼6.12,p<0.05) (F¼5.01,p<0.05) (F¼5.48,p<0.05). No significant changes were noted in DSST and E-MALT. Discussion: Better performance after offline-true tDCS session as well as online-sham tDCS session meant both tDCS and sternberg’s task influenced in enhancing the WM performance across the session. Paradoxical failure of online-tDCS to enhance WM performance may be related to the aberrant plasticity in Schizophrenia which might attain a transitional ceiling on combining the two plasticity modulators. The transferability of improvement to other cognitive domains could not be appreciated. Keywords: Online-tDCS, Cognitive deficits, Schizophrenia, Working memory
[0391] PHASE OF BRAIN OSCILLATIONS DETERMINES THE DIRECTION OF INDUCED PLASTICITY IN REAL-TIME EEG-TRIGGERED TMS C. Zrenner*, P. Belardinelli, D. Desideri, U. Ziemann. University of Tübingen, Germany Introduction: Can the large intra- and inter-individual variability of the effects induced by different repetitive TMS protocols be explained by the dynamics of ongoing activity at the time of stimulation? This study examined the influence of endogenous sensorimotor 10 Hz alpha rhythm on corticospinal plasticity Methods: A custom-built millisecond-accuracy real-time signal processing system was used to trigger repetitive TMS bursts according to the instantaneous phase of sensorimotor rhythm. Each burst was triggered either during the EEG surface positive peak or the surface negative peak of the local mu-rhythm. Single TMS pulses were applied before and after the intervention to assess the plasticity effect on corticospinal excitability. Results: A sequence of 200 repetitive TMS bursts (triple pulses of 100 Hz) delivered over a period of ca. 200 seconds resulted in a long-term (>30 min) increase of corticospinal excitability if triggered consistently at the EEG surface negative peaks of the mu-alpha oscillation, whereas the same TMS bursts triggered at the positive peaks decreased corticospinal excitability. Discussion: TMS triggered by a specific phase of an endogenous oscillation is a suitable tool to study the spatiotemporal properties of cortical dynamics and to induce reliable neuromodulatory effects in the human brain. In light of the results of this study, a realisation of the full therapeutic potential of brain stimulation in the treatment of brain network disorders will require a closed-loop approach that synchronises each stimulus with the individual patient’s instantaneous brain state. Keywords: real-time, closed-loop, neuromodulation [0394] MODULATION OF PHYSIOLOGIC ARTIFACTS DURING CONCURRENT TDCS AND EEG N. Gebodh*1, D. Adair 2, K. Chelette 3, Z. Esmaeilpour 1, 4, M. Bikson 1, J. Dmochowski 1, L.C. Parra 1, A.J. Woods 5, E. Kappenman 6. 1 The City College of New York, USA; 2 The Graduate Center at City University of New York, USA; 3 ANT Neuro North America, USA; 4 Amirkabir University of Technology, Iran; 5 University of Florida, USA; 6 University of California, USA Introduction: The field of non-invasive brain stimulation (NIBS) has benefited from integration with imaging including magnetic resonance imaging (MRI) and electroencephalography (EEG). Several studies have reported on concurrent tDCS and EEG, and used signal processing of varying complexity (e.g. high-pass filtering to ICA) to remove “non-physiologic stimulation artifacts” - namely artifacts arising from non-ideal stimulation and recording amplifier performance. None has compressively addressed “physiologic artifacts” which are defined here as non-stationary changes in artifacts resulting from interactions between the stimulation induced voltage and body. We identified and systematically characterized a series of tDCSinduced physiologic and nonphysiologic artifacts during concurrent EEG and High Definition (HD)-tDCS with physiological monitoring, and adapted MRIderived computational modeling to corroborate physiologic EEG findings. Methods: Subjects underwent three main simulation routines including 1) repeated, randomized, brief stimulation intensities over varied montages; 2) single intensity, randomized stimulation devices over a single montage; and 3) single device stimulation over a long duration with varied montages. Dosages ranged from 0.5-2.0 mA over 0.5-10 mins. Results: We identify and characterize three classes of artifacts including inherent stimulator artifacts, inherent physiologic artifacts, and noninherent artifacts. Physiologic artifacts included 1) cardiac distortion; 2) ocular motor distortion; 3) movement (myogenic) distortion. The power and voltage distribution of these artifacts were modulated in a tDCS montage, intensity, and polarity specific manner.