K. Hosomi

S109 Magnetoencephalographic-based brain–machine interface robotic hand for controlling sensorimotor cortical plasticity and phantom limb pain

Objectives Phantom limb pain is neuropathic pain after amputation of a limb and partial or complete deafferentation such as brachial plexus root avulsion. The underlying cause of this pain has been attributed to maladaptive plasticity of the sensorimotor cortex. It has been suggested that experimental reorganization would affect pain, especially if it results in functional restoration. We tested the hypothesis that restoration of hand motor function using a brain–machine interface (BMI) based on magnetoencephalographic (MEG) signals will normalize maladapted cortical representation and relieve pain. Methods This study included 10 phantom limb patients (9 brachial plexus root avulsion and 1 amputee). MEG signals during movements of the phantom hand or intact hand were used to train the decoder inferring movements of each hand. The robotic hand was controlled by the decoder. Patients controlled the robotic hand by moving the phantom hand. The training effects were compared among trainings with the phantom decoder, real hand decoder, and random decoder in a randomized cross-over trial. Results BMI training with the phantom decoder increased the decoding accuracy of phantom hand movements and pain. In contrast, BMI training with the intact hand decoder reduced accuracy and pain. Discussion It was suggested that BMI training to modulate the motor representation of phantom hand controlled pain. The sensorimotor cortical plasticity might induce pain. Conclusions and Significance Phantom limb pain was controlled by BMI training to induce sensorimotor cortical plasticity.

PTMS21 Cortical excitability changes in high-frequency repetitive transcranial magnetic stimulation for central post-stroke pain

Objectives: To investigate inter-individual variation in the efficiency of BST with regard to the stimulation site. Methods: We studied 31 healthy subjects, using a right hand muscle as a recording site. Three stimulation sites were compared: BST over the inion (inion BST), and BST over the midpoint between the inion and the right (ipsilateral BST) or left (contralateral BST) mastoid process. Five suprathreshold BSTs were performed for each stimulation site using the same stimulation intensity. The mean peak-to-peak amplitudes of MEP were compared. The active motor threshold (AMT) and onset latency for inion BST and ipsilateral BST were also measured and compared. Results: Contralateral BST did not evoke discernible MEPs in most subjects. In 21 subjects (67.7%), ipsilateral BST elicited larger MEPs than inion BST, and AMT for ipsilateral BST was lower than or equal to the AMT for inion BST in all subjects. Ipsilateral BST elicited shorter latency in such subjects, when MEP amplitudes were adjusted. Conclusions: The suitable stimulation site for BST differed among subjects. About two-thirds showed larger MEP to ipsilateral BST. Efficient stimulation site needs to be searched before the main examination.

P20.1 Efficacy of repetitive transcranial magnetic stimulation for neuropathic pain

Introduction: With the introduction of repetitive TMS (rTMS) it has been possible to study the modulatory effects of various stimulation paradigms on the excitability of motor systems. The outcomes are representative of the diverse effects of rTMS dependant on both the intensity and frequency of stimulation (Houdayer et al. 2008). Most studies investigate these effects on the motor evoked potentials of resting or slightly active muscles. The influence of magnetic stimulation on maximum voluntary contraction force the upper extremity muscles have not been studied with different stimulation paradigms. Methods: In this study we examined the effects of ‘simple’ rTMS at 5 Hz and theta burst stimulation paradigm (30 Hz 3 pulse burst at 5 Hz) on grip strength of healthy 18 35 year-old male subjects. An adjustable dynamometer (Jamar) was used to measure the grip strengths on Position-2 and Position-3 separations. Measurements were carried out before and after rTMS intervention with 300 pulses delivered to the forearm representation of motor cortex at 80% active motor threshold. Each participant was also subjected to sham stimulation in their first session. Results: The preliminary results suggest that there is no statistically significant change in the grip strength with either stimulation paradigm. However, a slight post-stimulation reduction in average grip strengths for both positions was observed in both ‘real’ and ‘sham’ stimulation sessions and this effect was less prominent after real-stimulation sessions. Conclusions: The results so far do not support the hypothesis that the stimulation protocols used in the study would significantly alter maximal voluntary contraction of isometric grip strength. The slight reduction observed in post-stimulation sessions could be due to fatigue. As this effect was generally weaker with the experimental rTMS protocols it could suggest a TMS induced resistance to fatigue.

P6.21 The effects of bilateral deep brain stimulation of the subthalamic nucleus (STN-DBS) on temperature sensation in patients with Parkinson's disease

Introduction and Objectives: PD is characterized by various changes in motor excitability. The present study was designed to examine through TMS cortical excitability and to specifically address inter-hemispheric connections in an uniform population of asymmetric PD-patients. Patients and Methods: A group of 14 PD patients with a predominant left hemibody involvement entered the study. Mean age was 60.7 y, 7 were females. Nine normal subjects, age and sex matched were the control group. Patients and normal controls underwent the evaluation of Motor Threshold (MT) and ipsilateral Silent Period (iSP), a negative TMS phenomenon induced by focal suprathreshold TMS on the ipsilateral motor cortex, measured as the suppression of voluntary EMG activity. Involuntary muscular activation during selective unilateral movements in homologous contralateral muscles, known as Mirror Movements (MM) were electromiographically recorded in three upper limb muscles in every subjects. Patients underwent clinical evaluation and were studied during two conditions: at the baseline (OFF) and after a levodopa load (ON). MT, iSP_entity (% of baseline EMG) and MM were compared with a group of 9 controls. Results: An altered movement lateralization exists in PD-patients, with MM mainly observed in the right arm during the voluntary activation of the left, more affected side (inter-side analysis: p = 0.03; intergroup analysis: p = 0.05). PD-patients showed a reduction in righthemisphere-MT, more affected, compared both to the contralateral one (p = 0.03) and to controls (p < 0.001). An increased right-iSP_entity was also detected in the PD group both versus the contralateral limb (p = 0.04) and versus controls (p = 0.008). No net effects of levodopa were detected on single neurophysiologic parameters. Interestingly in PD MMs exhibited by the right side correlate either with the iSP_entity, either with the motor involvement of the voluntary activated contralateral side. This is particularly true for the parkinsonian subjects exhibiting a milder pathological condition (n = 9; p = 0.013; Spearmann’s coefficient = 0.782). Conclusions: The defective movement lateralization in PD suggests that the connections between the two motor cortices are in some way malfunctioning, and probably linked to the asymmetrical motor involvement and to a defective interhemispheric balance.

P5-23 Deep brain stimulation of the subthalamic nucleus improves temperature sensation in Parkinson's disease

independently chosen for chronic DBS (Spearman’s rho = 0.35, p = 0.01). In addition, the absolute difference between the depths of the initial increase in beta and the contact chosen for chronic DBS correlated with the voltage used for chronic stimulation (rho = 0.322, p = 0.017). Thus more voltage had to be employed if a depth was selected for chronic stimulation that differed from that of the beta generator. Conclusions: On-line spectral analysis of LFPs recorded from the DBS electrode may help identify the optimal therapeutic target in the STN region for DBS.

S36-5 Event-related oscillatory changes: a key to elucidating neural processes

We observed that incoherent (random) dots motions evoked speed dependent MEG responses as coherent motions, the estimated origins of which were around the human MT/V5+ (Maruyama et al., Neurosci. Res. 2002). The results leaded to the idea that the human visual system processes motion information with the two scalars (direction and speed) instead of motion vectors. We have accumulated the evidence that supported this idea with psychophysical and physiological studies: In various motion stimuli composed of numerous red and green dots, observers perceived that peripheral dots moved similarly as central dots based on the same direction or speed even when either one of them was different, indicating that direction and speed of local motion can be processed separately and their distributions are analyzed independently (Kaneoke, et al., Neuroreport 2006). In MEG study, coherent motions with varied speeds and directions were presented using random dot kinematogram. Peak latency of the response to the motion onset was inversely related to the speed for all the directions. The mean mutual information entropy calculated using 4 response data with different directions revealed that the value exceeded more than 2 after the motion onset, indicating that the response signal can indeed carry information of more than 4 directions. The value was related to the coherence level but was less affected by the motion speed (Kaneoke et al., Neuroscience 2009). The direction information was represented in the response waveform evoked by the random dot pattern that did not have physical speed information (Oka, et al., in submission). The results indicate that direction and speed are represented in the response waveform separately. We consider that the visually detected motion information is spatially integrated as motion scalars even though motions might be detected and represented as vectors locally.

S16-2 Neurophysiological approach to language function based on event-related oscillatory changes: from functional mapping to brain-machine interface

S16-2 Neurophysiological approach to language function based on event-related oscillatory changes: from functional mapping to brain-machine interface M. Hirata1,2, T. Goto1,2, T. Yanagisawa1, M. Inui2, H. Tamura1, Y. Saitoh1, K. Hosomi1, T. Maruo1, M. Shayne1, S. Yorifuji2, T. Yoshimine1 1Department of Neurosurgery, Osaka University Medical School, Suita, Japan, 2Division of Functional Diagnostic Science, Osaka University Graduate School of Medicine, Suita, Japan

P11-9 Cortical excitability changes in high-frequency rTMS for central post-stroke pain

Introduction: Slow rate repetitive transcranial magnetic stimulation (rTMS) has been employed in treatment of mood disorders for more than decade ago. Previous clinical studies employed different localisations and stimulation frequency aiming to produce better clinical effects. We have designed sham-controled 1 Hz slow-rate tonic rTMS combined with partial sleep deprivation in treatment of major depression. Methods: Seventeen patients (48.2±6.1 yrs) with diagnosis of unipolar major depression, with unsatistfying theraputic response (Hamilton depression score, HAMD less than 18), on stable pharmacotherapy (more than 4 weeks) were treated with rTMS (1 Hz) at threshold intensity, over right dorso-lateral prefrontal cortex, during two weeks (10 session); 5 trains (60 stimuli per session). Twice during the period of two weeks partial sleep deprivation was applied (4 h/per night). Theraputic effects were estimated by blind rater experienced in HAMD and clinical global impression (CGI) scores, two and three weeks after stimulation. Results: Active rTMS (9 patients) has shown HAMD score reduction 26.12±2.11 (pre-stimulation) to 14.24±1.75 (two weeks later), and 15.21±5.21 (three weeks later) contrary to almost complete theraputic failure among sham-treated patients (24.98±1.94, pre-; 21.68±3.11, after two weeks; 24.08±3.21 after three weeks). CGI improvement were observed among rTMS treated patients as well (4.66±0.67, baseline; 2.97±0.53, after two weeks; 2.75±0.71, after three weeks) while sham treated has shown no changes (4.19±0.32, baseline; 4.06±0.65, after two weeks; 4.18±0.91, after three weeks). Conclusion: Our results suggest clinicaly relevant reponse when slow rate tonic rTMS is additionaly boosted with partial sleep deprivation in in patients with pharmacoresistant depression. Further experiments are recommended in aim to determine optimal parameters of stimulation as well as pattern of sleep deprivation.