32 Relationship between intrinsic intracortical inhibition and rate of motor skill learning Yoshiki Koizume a , Masato Hirano a , Shinji Kubota a,c , Shigeo Tanabe b , Kozo Funase a a Human Motor Control Laboratory, Graduate School of Integrated Arts and Sciences, Hiroshima University, Japan b Faculty of Rehabilitation, School of Health Sciences, Fujita Health University, Japan c Research Fellow of the Japan Society for the Promotion of Science Purpose: In motor skill learning, time to reach the plateau phase is different among the subjects. However, the details of the inter-in- dividual difference of learning rate are still unknown. Which factors are associated with individual’s learning rate? Previous studies have demonstrated that the reduction of GABA in primary motor cortex (M1) has important role in motor skill learning. Therefore, we hypothesized that the subjects who have weak intracortical inhibition in M1 learn faster than the subjects who have strong intracortical inhibition. Here, we investigated the role of intrinsic intracortical inhibition and the rate of motor skill learning. Methods: Twenty subjects participated in this study. First, we recorded the short- and long-interval intracortical inhibitions (SICI/ LICI) and cortical silent period (SP) in the tibialis anterior muscle evoked by transcranial magnetic stimulation (TMS). These re- cordings were carried out during weak isometric dorsiflexion. SICI and LICI were assessed by double-TMS paradigm. The intensities of conditioning stimuli (CS) for measuring SICI were set to 70, 80, and 90% of the active motor threthold (aMT). And the intensity of test stimuli (TS) was adjusted to evoke a MEP of approximately 1mV. Interstimulus intervals were set to 3ms for SICI and 100ms for LICI, respectively. SP was induced bya single TMS at 140% of aMT. After these measurements, subjects learned a visuomotor tracking task performed by ankle dorsiflexion and plantarflexion. Results and Discussion: In accordance with our hypothesis, we found the clear relationship between the SICI and learning rate. Subjects who have weaker intrinsic SICI learn the task faster. No relationships, however, were found between the LICI/SP and learning rate. These results suggest that the intrinsic intra- cortical GABA system may affect the inter-individual difference of learning rate. 33 Short-latency afferent inhibition from the motor and dorsolateral prefrontal cortex in healthy subjects: a combined TMSeEEG study Yoshihiro Noda a, * , Robin F. Cash a,b , Luis Garcia Dominguez a , Faranak Farzan a , Tarek K. Rajji a , Robert Chen b , Zafiris J. Daskalakis a , Daniel M. Blumberger a a Centre for Addiction and Mental Health, Department of Psychiatry, University of Toronto, Canada b Division of Neurology, Krembil Neuroscience Centre, Toronto Western Research Institute, University Health Network, University of Toronto, Canada *E-mail: Yoshihiro.Noda@camh.ca. Introduction: Short-latency afferent inhibition (SAI) is a TMS neurophysiological paradigm that represents an index of central cholinergic activity over the motor cortex. However, SAI effect has not been identified in the prefrontal cortex, especially at the dorsolateral prefrontal cortex (DLPFC), which area is closely related to cognition. We aimed to investigate the SAI effect at the DLPFC in healthy subjects. Methods: Twelve healthy subjects participated. The combined TMS-EEG technique was applied in this study. The median nerve in the right wrist and M1 hot spot was stimulated in M1-SAI paradigm while DLPFC (F5) was stimulated in DLPFC-SAI paradigm. The interstimulus interval (ISI) of N20 and N20+2 ms was used for M1-SAI while the ISI of N20 to N20+10 increases by 2 ms and N20+20 ms were applied for DLPFC-SAI. Individual N20 latency was measured from somatosensory-evoked potentials (SEP) prior to the SAI procedure. TMS-evoked potentials (TEPs) were obtained after cleaning of EEG with independent component analysis. Analysis of variance (ANOVA) for each value of TEPs and spearman’s correla- tion analysis between SAI-MEP and N100-TEP amplitude changes were performed. Results: In M1-SAI, 3-way ANOVA with ISI, latency component, and area as within-subject factors and post-hoc t-tests showed signifi- cant N100-TEP amplitude attenuation over the midline central area (N20+2; p ¼ 0.002). Further, there is a significant correlation be- tween MEP and N100-TEP amplitude attenuation over the midline central area (rho ¼ 0.009, p ¼ 0.713). In DLPFC-SAI, the ANOVA and post-hoc t-tests indicated significant attenuation on the N100-TEP components (N20+4; p ¼ 0.003) over the midline central area. Conclusions: This is a first study to investigate SAI effect over the DLPFC. Our findings replicate previous M1-SAI studies. The measure of SAI in the DLPFC could potentially enhance our understanding of neurophysiology in healthy and diseased states. 34 Present and future clinical applications of tDCS Michael A. Nitsche Dept. Clinical Neurophysiology, University Medical Center, Georg- August-University, Goettingen, Germany Introduction: Numerous neurological diseases are accompanied by pathological alterations of neuroplasticity, and a central aspect of rehabilitation, i.e. re-learning of functions, involves plasticity, too. Therefore, modulation of plasticity by brain stimulation tools is promising for therapy of neurological diseases. tDCS induces plas- ticity via the induction of weak direct currents through the scalp, and has been suggested to improve clinical symptoms in diverse neurological diseases. Methods: An overview of the state of the art for clinical application of tDCS in neurological diseases will be given, including limitations, and future directions of research and clinical application. Results: tDCS has been shown to improve motor rehabilitation, as well as aphasia, neglect, and swallowing after stroke. Furthermore, pilot studies suggest a positive effect on pain syndromes, tinnitus, fatigue in multiple sclerosis, cognitive decline in neurodegenerative disorders, and epilepsy. Most of the available studies are pilot trials with small numbers of subjects, stimulation protocols differ rele- vantly between studies, and effect size is often limited. Basic neurophysiological, and modelling studies deliver concepts how to enhance the efficacy of stimulation, e.g. by specific repetition in- tervals, altering the intensity of stimulation, and more targeted stimulation. Discussion: The results of pilot studies are in favour for relevant clinical effects of tDCS, but optimized stimulation protocols are needed to improve the efficacy of stimulation. For transferring tDCS into clinical routine, pivotal multi-center clinical trials are needed. 35 Efficacy, Relaps And Cognitive Side Effects After Brief Pulse And Ultrabrief Pulse Right Unilateral Electroconvulsive The For Major Depression: A Randomised Double Blind Controlled Study Harm-Pieter Spaans MD, HP a, * , Esmée Verwijk MSc a , Hannie C. Comijs PhD b,c , Rob M. Kok MD, PhD a , Pascal Sienaert MD, PhD e , Filip Bouckaert MD e , Katrien Fannes MSc e , Koen Vandepoel MSc e , Erik J.A. Scherder PhD d , Max L. Stek MD, PhD c , King H. Kho MD, PhD a a Parnassia Psychiatric Institute, The Hague, The Netherlands Abstracts / Brain Stimulation 8 (2015) 310e325 316