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Amplitude of motor evoked potentials at rest is positively correlated with EEG-oscillations over sensorimotor cortex
254
Abstracts
actions. Thus, differential mirror motor facilitation during starting and end postures cannot be ascribed to the reading of the finger kinematics at different hand apertures. Result: We found that the observation of the starting position and middle phases of both actions engendered a significantly higher motor facilitation than observing their final postures.
Observing the final postures of both grip and throw actions did not activate the motor system independently from the different finger configuration. Motor facilitation during observation of starting and middle positions was specific for the FDI muscle which would be activated during actual execution of the observed actions. Subjective ratings obtained at the end of the recording session (Fig. 3) showed that differential modulation of motor facilitation was not due to the amount of implied motion per se but to the forward direction of the motion path.
Method: Corticospinal excitability was indexed by the peak-to-peak amplitude of motor potentials (MEP) evoked in the relaxed right abductor pollicis brevis muscle by focal transcranial magnetic stimulation (TMS) of the left primary motor cortex. EEG was analyzed in the 2 sec segment immediately preceding the TMS pulse. EEG was also recorded in the same experimental session when the subjects performed self initiated thumb flexions. Eight healthy volunteers (4 female) participated in the study. About 500 manually triggered TMS pulses were delivered over w2 hours. Result: With no prior assumptions a difference was found in average EEG spectra between one third of trials with the highest MEP amplitude and one third of trials with the lowest MEP amplitude. The association emerged chiefly at a scalp region overlying the contralateral sensorimotor cortex, in two distinct frequency bands (alpha, 6.5-11.5 Hz and beta, 17.5-39.5 Hz). Higher MEP amplitude was associated with increased EEG power. The power differences were significant at the group level for both frequency bands (p , 0.05). The spectral power pattern resembled the decrease of spectral power related to voluntary muscle activation (known as eventrelated desynchronisation, ERD) in both frequencies and gross topographical distribution. However, detailed source analysis indicated that the source modulated with MEP amplitude was more anterior and lateral than the source modulated by movement. Weak, but significant (p , 0.05) positive correlation across trials between MEP amplitude and EEG power was found in 6 subjects. Significance was not affected by partialing out the effect of slow trends in both time series. No consistent relation was found between the phase of the EEG immediately before TMS and MEP amplitude. Conclusion: These findings suggest that local oscillations may modulate neuronal excitability in the absence of specific motor activity. Neuronal oscillations may have a different functional role in the resting, active, and previously active motor cortex. The project was supported by DAAD.
tDCS Poster Only 49
Repetitive transcranial direct current stimulation improves hyperalgesia and allodynia in a CRPS patient
Knotkova H1, Feldman D2, Factor A2, Sibirceva U1, Dvorkin E1, Cohen L3, Ragert P4, Cruciani RA1, 1Beth Israel Medical Center (New York, US); 2Montefiori Hospital (New York, US); 3National Institute of Health/NINDS (Bethesda, US); 4University of Duesseldorf (Duesseldorf, DE)
Conclusion: The results show that motor facilitation is specific for the observation of snapshots evoking ongoing but incomplete actions. This suggests that the motor cortico-spinal component of the observationexecution matching system is preferentially activated by the inner anticipatory simulation of the deployment of an action in the future.
TMS Poster Only 48
Amplitude of motor evoked potentials at rest is positively correlated with EEG-oscillations over sensorimotor cortex
Litvak V1, Zeller D2, Oostenveld R3, Maris E4, Zaaroor M5, Pratt H5, Classen J2, 1University College London (London, UK); 2University of Wuerzburg (Wuerzburg, DE); 3F.C. Donders Centre for Cognitive Neuroimaging (Nijmegen, NL); 4University of Nijmegen (Nijmegen, NL); 5 Technion - Israel Institute of Technology (Haifa, IL) Objective: Oscillations of neuronal activity abound in human cortex, yet their functional significance is only partly understood. Here we used wideband 64-channel electroencephalographic (EEG) recordings and nonparametric permutation analysis to examine the relationship between oscillatory brain activity and motor corticospinal excitability.
Limited evidence suggests that the repetitive anodal tDCS (i.e. applied on 5 consecutive days) over the motor cortex relieves neuropathic pain. Up to date, there are no published findings on efficacy of tDCS to alleviate hyperalgesia and/or allodynia, symptoms that are very often associated with presence of neuropathic pain. In our study, we evaluated a long-term use of repetitive tDCS for alleviation of pain, hyperalgesia and allodynia in a patient with Complex Regional Pain Syndrome (CRPS). Here, we present our findings only on the tDCS efficacy to improve hyperalgesia and allodynia associated with CRPS, as our results on pain relief have already been presented elsewhere (Knotkova et al., 2008). Methods: A CRPS patient whose intractable neuropathic pain in a lower limb did not respond to conventional therapy received a total of 5 blocks of 5 daily sessions each of anodal tDCS applied over the primary motor cortex over the course of 42 weeks. Each tDCS application consisted of 20 min of anodal tDCS at current intensity of 2 mA, the active electrode was placed over the primary motor cortex, at the position of C3 of the international EEG classification. Mechanical hyperalgesia (HY) and mechanical allodynia (AL) were evaluated in the affected and non-affected limb before and 30 min after each tDCS session using Von Frey filaments, cotton swab, cotton Q-tip and brush. The procedure followed the Comprehensive protocol for quantitative sensory testing for clinical trials (Rolke et al., 2005). The study was approved by the Beth Israel Hospital IRB. Results Prior to the first application of tDCS, HY in the affected limb was 10.95 (out of 100) and improved by 73% after the first block (5 sessions) of tDCS, decreasing to 2.85. During following tDCS blocks, HY in the affected limb
Abstracts
actions. Thus, differential mirror motor facilitation during starting and end postures cannot be ascribed to the reading of the finger kinematics at different hand apertures. Result: We found that the observation of the starting position and middle phases of both actions engendered a significantly higher motor facilitation than observing their final postures.
Observing the final postures of both grip and throw actions did not activate the motor system independently from the different finger configuration. Motor facilitation during observation of starting and middle positions was specific for the FDI muscle which would be activated during actual execution of the observed actions. Subjective ratings obtained at the end of the recording session (Fig. 3) showed that differential modulation of motor facilitation was not due to the amount of implied motion per se but to the forward direction of the motion path.
Method: Corticospinal excitability was indexed by the peak-to-peak amplitude of motor potentials (MEP) evoked in the relaxed right abductor pollicis brevis muscle by focal transcranial magnetic stimulation (TMS) of the left primary motor cortex. EEG was analyzed in the 2 sec segment immediately preceding the TMS pulse. EEG was also recorded in the same experimental session when the subjects performed self initiated thumb flexions. Eight healthy volunteers (4 female) participated in the study. About 500 manually triggered TMS pulses were delivered over w2 hours. Result: With no prior assumptions a difference was found in average EEG spectra between one third of trials with the highest MEP amplitude and one third of trials with the lowest MEP amplitude. The association emerged chiefly at a scalp region overlying the contralateral sensorimotor cortex, in two distinct frequency bands (alpha, 6.5-11.5 Hz and beta, 17.5-39.5 Hz). Higher MEP amplitude was associated with increased EEG power. The power differences were significant at the group level for both frequency bands (p , 0.05). The spectral power pattern resembled the decrease of spectral power related to voluntary muscle activation (known as eventrelated desynchronisation, ERD) in both frequencies and gross topographical distribution. However, detailed source analysis indicated that the source modulated with MEP amplitude was more anterior and lateral than the source modulated by movement. Weak, but significant (p , 0.05) positive correlation across trials between MEP amplitude and EEG power was found in 6 subjects. Significance was not affected by partialing out the effect of slow trends in both time series. No consistent relation was found between the phase of the EEG immediately before TMS and MEP amplitude. Conclusion: These findings suggest that local oscillations may modulate neuronal excitability in the absence of specific motor activity. Neuronal oscillations may have a different functional role in the resting, active, and previously active motor cortex. The project was supported by DAAD.
tDCS Poster Only 49
Repetitive transcranial direct current stimulation improves hyperalgesia and allodynia in a CRPS patient
Knotkova H1, Feldman D2, Factor A2, Sibirceva U1, Dvorkin E1, Cohen L3, Ragert P4, Cruciani RA1, 1Beth Israel Medical Center (New York, US); 2Montefiori Hospital (New York, US); 3National Institute of Health/NINDS (Bethesda, US); 4University of Duesseldorf (Duesseldorf, DE)
Conclusion: The results show that motor facilitation is specific for the observation of snapshots evoking ongoing but incomplete actions. This suggests that the motor cortico-spinal component of the observationexecution matching system is preferentially activated by the inner anticipatory simulation of the deployment of an action in the future.
TMS Poster Only 48
Amplitude of motor evoked potentials at rest is positively correlated with EEG-oscillations over sensorimotor cortex
Litvak V1, Zeller D2, Oostenveld R3, Maris E4, Zaaroor M5, Pratt H5, Classen J2, 1University College London (London, UK); 2University of Wuerzburg (Wuerzburg, DE); 3F.C. Donders Centre for Cognitive Neuroimaging (Nijmegen, NL); 4University of Nijmegen (Nijmegen, NL); 5 Technion - Israel Institute of Technology (Haifa, IL) Objective: Oscillations of neuronal activity abound in human cortex, yet their functional significance is only partly understood. Here we used wideband 64-channel electroencephalographic (EEG) recordings and nonparametric permutation analysis to examine the relationship between oscillatory brain activity and motor corticospinal excitability.
Limited evidence suggests that the repetitive anodal tDCS (i.e. applied on 5 consecutive days) over the motor cortex relieves neuropathic pain. Up to date, there are no published findings on efficacy of tDCS to alleviate hyperalgesia and/or allodynia, symptoms that are very often associated with presence of neuropathic pain. In our study, we evaluated a long-term use of repetitive tDCS for alleviation of pain, hyperalgesia and allodynia in a patient with Complex Regional Pain Syndrome (CRPS). Here, we present our findings only on the tDCS efficacy to improve hyperalgesia and allodynia associated with CRPS, as our results on pain relief have already been presented elsewhere (Knotkova et al., 2008). Methods: A CRPS patient whose intractable neuropathic pain in a lower limb did not respond to conventional therapy received a total of 5 blocks of 5 daily sessions each of anodal tDCS applied over the primary motor cortex over the course of 42 weeks. Each tDCS application consisted of 20 min of anodal tDCS at current intensity of 2 mA, the active electrode was placed over the primary motor cortex, at the position of C3 of the international EEG classification. Mechanical hyperalgesia (HY) and mechanical allodynia (AL) were evaluated in the affected and non-affected limb before and 30 min after each tDCS session using Von Frey filaments, cotton swab, cotton Q-tip and brush. The procedure followed the Comprehensive protocol for quantitative sensory testing for clinical trials (Rolke et al., 2005). The study was approved by the Beth Israel Hospital IRB. Results Prior to the first application of tDCS, HY in the affected limb was 10.95 (out of 100) and improved by 73% after the first block (5 sessions) of tDCS, decreasing to 2.85. During following tDCS blocks, HY in the affected limb