The combination of transcranial magnetic stimulation (TMS) and electroencephalogram (EEG) is an effective tool for investigating the cortical reactivity and the functional connectivity in the brain. In our previous study, we reported a method of removing stimulus artifact during TMS with Sample-and-Hold circuit and EEG activity evoked by TMS could be measured successfully. In addition to this method, independent component analysis (ICA) was also applied to recorded EEG data in order to remove the stimulus artifact from for off-line analysis. By using these methods, short latency ( 15 ms) EEG responses to TMS could be obtained. In this paper, we focused on the propagation of EEG activity elicited by TMS. We observed both the EEG topography and the distribution of the current density over the whole head by changing the stimulus site. When motor cortex was stimulated, the propagation of EEG activity to contralateral hemisphere could be clearly observed. However, when posterior parietal cortex was stimulated, no or less propagation of EEG responses could be recognized. These results suggest that the responses evoked by TMS over motor cortex propagate to contralateral hemisphere along the axon through the corpus callosum.
Objectives The purposes of this study were to validate the Acoustic Breathiness Index (ABI) for the Japanese-speaking population and to determine whether it is independent of factors such as sex, age, and perceptual ratings of roughness. Method First, the concurrent validity of the ABI for perceptual breathiness was evaluated on the concatenations of continuous speech and sustained vowels from 288 patients with varying degrees of dysphonia. The diagnostic accuracy was examined on 343 samples with 55 additional normophonic speakers. Second, the validity related to responsiveness-to-change was estimated on 222 samples obtained before and after interventions for 111 voice-disordered patients. Third, the relationships between the ABI and other variables (i.e., perceptual hoarseness/breathiness/roughness, sex, and age) were explored using bivariate and multivariate analyses for the 288 patients. Results First, the concurrent validity and the responsiveness-to-change validity were confirmed by strong correlation coefficients of .890 and .878, respectively. Second, the receiver operating characteristic analysis showed the area under the curve to be 0.939, indicating excellent accuracy. The ABI of 3.44 exhibited a sensitivity of 76.3% and a specificity of 94.1%. Third, although bivariate analyses revealed a weak relationship between ABI and roughness and an ABI difference by age, multiple regression analyses showed a strong relation between only ABI and breathiness, without a meaningful contribution from roughness, sex, and age factors. Conclusion The study confirmed that the ABI is an accurate and specific tool to estimate breathiness levels in the Japanese-speaking population and neither roughness, sex, nor age significantly affects the ABI.
When the odd stimulation is presented, the positive component of electroencephalograph is induced at around 300 ms after the odd stimulation. This positive component is called P300. Many studies suggest that P300 may result from the summation of activity from multiple generators located in widespread cortical and subcortical areas. However, there is still no conclusive indication of the sources of P300. In this paper, we focus on the left supramaginal gyrus as one of the sources of P300. We investigated the temporal aspect of this area using TMS (transcranial magnetic stimulation). We investigated the relationship between the latency of the P300 and an effect of TMS when the left supramarginal gyrus was stimulated by TMS. In our previous study, we reported a method of removing stimulus artifact during TMS with Sample-and-Hold circuit and electroencephalogram (EEG) activity evoked by TMS could be measured successfully. In addition to this method, independent component analysis (ICA) was also applied to recorded EEG data in order to remove the stimulus artifact by off-line analysis. By using these methods, short latency (< 15 ms) EEG responses to TMS could be obtained. We stimulated the left supramarginal gyrus using a figure-eight coil during auditory oddball task. The TMS at 150 ms and 200 ms after the oddball sounds were presented. When the TMS was applied at 200 ms after the oddball stimulation, the peak response of P300 was delayed around 50 ms. Difference of the peak latency between the control measurement and the case of TMS applying at 150 ms was not significant. However, the differences of the peak latency of the control measurement and the peak latency of the measurement in the cases of TMS applying at 200 ms and 250 ms was significant (p<0.05). We considered that this delay was due to inhibiting to recognize the target stimulation.
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