Information processing of passive joint motion to spinal nervous system.

The purpose of this work was to investigate the information processing of passive joint motion of the rat hindlimb in the spinal nervous system in vivo. Action potentials using intracellular recordings and joint kinematics using video analysis were measured. The results show that the action potentials of the spinal nervous system-evoked passive joint motion were significantly changed. Therefore, physical therapy is one of the useful methods for the treatment of joint position and angular position sensitivity and spinal nervous system disorders.

Language/Culture Modulates Brain and Gaze Processes in Audiovisual Speech Perception.

Several behavioural studies have shown that the interplay between voice and face information in audiovisual speech perception is not universal. Native English speakers (ESs) are influenced by visual mouth movement to a greater degree than native Japanese speakers (JSs) when listening to speech. However, the biological basis of these group differences is unknown. Here, we demonstrate the time-varying processes of group differences in terms of event-related brain potentials (ERP) and eye gaze for audiovisual and audio-only speech perception. On a behavioural level, while congruent mouth movement shortened the ESs' response time for speech perception, the opposite effect was observed in JSs. Eye-tracking data revealed a gaze bias to the mouth for the ESs but not the JSs, especially before the audio onset. Additionally, the ERP P2 amplitude indicated that ESs processed multisensory speech more efficiently than auditory-only speech; however, the JSs exhibited the opposite pattern. Taken together, the ESs' early visual attention to the mouth was likely to promote phonetic anticipation, which was not the case for the JSs. These results clearly indicate the impact of language and/or culture on multisensory speech processing, suggesting that linguistic/cultural experiences lead to the development of unique neural systems for audiovisual speech perception.

Potential force dynamics of heart rate variability reflect cardiac autonomic modulation with respect to posture, age, and breathing pattern.

RATIONALE: Various physiological and pathological conditions are correlated with cardiac autonomic function. Heart rate variability is a marker of cardiac autonomic modulation and can be measured by several methods. However, the available methods are sensitive to breathing patterns. OBJECTIVES: To quantify cardiac autonomic modulation by observing the potential force dynamics of the R-R interval time series in healthy individuals. METHODS: We propose two "potentials of unbalanced complex kinetic" (PUCK) parameters to quantify the characteristics of the potential force dynamics of R-R interval time series: potential strength (slope) and fluctuation size (slope standard deviations [SSD1, SSD2]). We applied this method to the series of R-R intervals obtained from 30 healthy subjects in an experimental condition that elicited cardiac autonomic (i.e., sympathetic and vagal) activation (in supine, sitting, and standing positions). Subjects were categorized into three groups by decade (i.e., 20 s, 30 s, and 40 s) to verify the cardiac autonomic differences by age. Two respiration patterns were introduced to check the influence of the pattern into the analytical results. MEASUREMENTS AND MAIN RESULTS: Sympathetic modulation activation significantly increased the slope and reduced SSD1 and SSD2; these trends were confirmed in all groups. The slope is concordant with the result of the low frequency/high frequency (LF/HF) ratio in frequency components as an indicator of sympathetic modulation. No trend was observed in slope among age groups. However, SSD1 and SSD2 in the 40 s group were significantly decreased in the supine and sitting positions. The results with respect to respiration frequency showed lower sympathetic modulation as shown in the LF/HF ratio and slope, whereas higher vagal modulation as shown in the HF appeared with a longer breathing rate. CONCLUSIONS: PUCK can quantify the cardiac autonomic modulation in the experimental conditions of different postures. SSD1 and SSD2 are more sensitive to age than frequency components and are unaffected by breathing patterns. This method may be an alternative method for observing cardiac autonomic modulation in clinical practice.

Longitudinal changes of motor cortical excitability and transcallosal inhibition after subcortical stroke.

OBJECTIVE: A general lack of longitudinal studies on interhemispheric interactions following stroke led us to use transcranial magnetic stimulation (TMS) to examine changes in corticospinal/intracortical excitability and transcallosal inhibition over a 1-year period following subcortical stroke. METHODS: We measured TMS parameters such as motor threshold (MT), short-interval intracortical inhibition (SICI), and ipsilateral silent period (iSP) and evaluated clinical scores at three time-points (T1, T2, and T3) in 24 patients and 25 age-matched healthy subjects. RESULTS: At T1, we observed reduced MTs and SICIs with prolonged iSPs in the unaffected hemisphere (UH). In contrast, increased MTs and reduced SICIs were observed in the affected hemisphere (AH). These abnormalities gradually reduced and no MEP response to TMS at T1 predicted a worse prognosis. The prolonged iSP at T1 was associated with more severe impairments, but it did not necessarily predict a worse prognosis after 1year. CONCLUSIONS: UH excitability was increased at the post-acute time-period, which may have resulted in enhanced transcallosal inhibition to the AH. However, it is unclear whether there was a causal relationship between the enhanced transcallosal inhibition and the extent of clinical recovery. SIGNIFICANCE: This is the first study to demonstrate changes in transcallosal inhibition over a longitudinal period following stroke.

Cardiac arrhythmia detection using combination of heart rate variability analyses and PUCK analysis.

This paper presents cardiac arrhythmia detection using the combination of a heart rate variability (HRV) analysis and a "potential of unbalanced complex kinetics" (PUCK) analysis. Detection performance was improved by adding features extracted from the PUCK analysis. Initially, R-R interval data were extracted from the original electrocardiogram (ECG) recordings and were cut into small segments and marked as either normal or arrhythmia. HRV analyses then were conducted using the segmented R-R interval data, including a time-domain analysis, frequency-domain analysis, and nonlinear analysis. In addition to the HRV analysis, PUCK analysis, which has been implemented successfully in a foreign exchange market series to characterize change, was employed. A decision-tree algorithm was applied to all of the obtained features for classification. The proposed method was tested using the MIT-BIH arrhythmia database and had an overall classification accuracy of 91.73%. After combining features obtained from the PUCK analysis, the overall accuracy increased to 92.91%. Therefore, we suggest that the use of a PUCK analysis in conjunction with HRV analysis might improve performance accuracy for the detection of cardiac arrhythmia.

Fundamental study of measurement of cardiorespiratory signals in a sitting position using piezoelectric sensors.

In this paper, we propose a measurement system to extract the heartbeat and respiration signals from piezoelectric sensors located in a chair seat. Eight healthy male subjects (22-26 years old) sat on a chair with piezoelectric sensors. The experiment consisted of five acquisitions (300 s recording with 30 s resting). In the 1st acquisition, the subject was instructed to maintain a relax state. During the next three acquisitions, the subject maintained respiration rates of 3, 4, and 5 s. The order was randomly given for each subject. Finally, the subject was instructed to stay in a resting state for 300 s. Band-pass filters were used to separate the heartbeat and respiration signals from the output signal of the piezoelectric sensors (heartbeat: 0.7-7 Hz, respiration: 0.1-0.4 Hz). Then, the standard heartbeat interval was calculated using the autocorrelation function to generate a template. Heartbeat and respiration signals were extracted using a two-dimensional cross-correlation pattern matching method. For validation, the error ratio between the piezoelectric sensor data and the reference data was determined. The error ratios of the heartbeat interval and respiration interval were 2.89 ± 4.41% and 5.57 ± 4.42%, respectively. Therefore, it is suggested that heartbeat and respiration signals extracted from piezoelectric sensors in a sitting position can be used as an alternative method for extracting biological signals.

Event-related potential study on image-symmetry discrimination in the human brain.

The human visual system seems to have a highly perceptual sensitivity to symmetry. However, where and when the discrimination of symmetrical properties begins in the context of visual information processing is largely unclear. This study investigates event-related potential (ERP) patterns in humans when perceiving symmetry-varied complex object images. ERP responses were derived from electroencephalography (EEG) data recorded from eight healthy subjects using 128-channel scalp electrodes. Visual stimulation was provided using gray-scaled photographs of a car with six different viewpoints, hence disrupting the vertical symmetry, where one of the stimuli was intentionally made symmetric by mirroring the image about its center vertical axis. The results show that discrimination of image symmetry is revealed by potential deflection in early ERP components recorded at occipito-temporal sites and can be significantly observed around 220 ms after stimulus onset.

A novel EEG index for evaluating the sleep quality in patients with obstructive sleep apnea-hypopnea syndrome.

Obstructive sleep apnea-hypopnea syndrome (OSAHS) is a highly prevalent sleep disorder characterized by recurrent episodes of oxygen desaturation during sleep, decreased sleep quality, and excessive daytime sleepiness. A basic method of evaluating sleep quality is polysomnography (PSG) where sleep stages are identified from the electroencephalogram (EEG), electrooculogram and chin electromyogram. The implementation of PSG is limited to sleep laboratories because this test is rather complicated to perform and quite time-consuming to analysis, requiring skilled technicians. Development of simple alternative methods to PSG could enable sleep tests to be performed at home. Our study aimed to identify simple measures for evaluating the sleep quality. We focused on a simple index, entropy, which is derived from power spectrum of EEG signals throughout the night, and reflects the dynamics of EEG signals, and examined whether the entropy of EEG reflects the sleep quality of OSAHS. The EEG signals for the analysis of EEG entropy were recorded from the temple area. The EEG entropy was compared with the sleep quality by traditional approaches of EEG from PSG in 58 OSAHS patients and 8 healthy volunteers. The EEG entropy in each subject showed the negative values and fluctuated during sleep. There was a significant correlation between the EEG entropy and the sleep quality (r = 0.626, p < 0.001); namely, the amplitude of the fluctuation was increased with the increase in the sleep quality. We therefore propose that the EEG entropy could be useful for evaluating the sleep quality of OSAHS.

A new method for localizing the sources of correlated cross-frequency oscillations in human brains.

Anatomically distributed areas are dynamically linked to form functional networks for processing and integrating the different modalities of information in the human brain. A part of such networks is considered to be realized with synchronization of neuronal activities, which can generate correlated neural oscillation at the same and/or different frequency bands. To investigate the networks with the synchronization, analysis of connectivity between not only same frequency oscillation but also different frequency (i.e. cross-frequency) is needed. For source estimation with electroencephalogram (EEG) or magneto-encephalogram (MEG) signals, a spatial filtering technique is recently applied as an alternative method for equivalent current dipole (ECD) estimation technique. Non-adaptive type of spatial filtering technique, such as the Standardized low-resolution brain electromagnetic tomography (sLORETA), is reported to discriminate correlated sources. However, it may lead to inaccurate results due to its low spatial resolution. In the present study, we proposed a new systematic approach for localizing the sources of correlated cross-frequency oscillations. The method we propose can overcome the limitation of the non-adaptive spatial filtering technique by proactively using identified information in sensor level analysis (e.g. cross-correlation map and correlation topography), which allow us to focus on target sources. The performance of our proposed method is evaluated with simulated EEG signals, and is compared with traditional method.

[Examination of spirometry techniques on instruction by medical technologists for screening purposes].

BACKGROUND: The burden of chronic obstructive pulmonary disease (COPD) remains very high. Current consensus guidelines emphasize the importance of the early detection of COPD, but its underdiagnosis is common in general practice. Spirometry is the "gold standard" in the diagnosis of COPD. However, it remains underused in general practice because the application of spirometry is viewed as difficult to obtain accurate results. AIMS: To clarify the accuracy of spirometry techniques for screening purposes. METHOD: Subjects (n = 142) were told about the spirometry procedure using pre-determined descriptions, followed by the first spirometry test. Special medical technologists gave instructions on the detailed spirometry procedure on reference to the first test of results, and the second spirometry test was performed. The second spirometric indices, SVC, FVC, FEV1, FEV1%, and PEF, were compared with the first ones. RESULTS: The instruction by special medical technologists significantly improved all spirometric indices except for FEV1%. For a diagnosis of restrictive disorder (VC<80%), the impact of intervention by the special medical technologists was highly significant (p<0.001). In contrast, for the diagnosis of obstructive disorder (FEV1%<70%), the impact was small. CONCLUSION: To detect obstructive disorder, the high-level accuracy of special spirometry techniques is not always necessary.

[Evaluation of a simplified index (spectral entropy) about sleep state of electrocardiogram recorded by a simplified polygraph, MemCalc-Makin2].

BACKGROUND: Polysomnography (PSG) is the gold standard for the diagnosis of sleep apnea hypopnea syndrome (SAHS), but it takes time to analyze the PSG and PSG cannot be performed repeatedly because of efforts and costs. Therefore, simplified sleep respiratory disorder indices in which are reflected the PSG results are needed. The Memcalc method, which is a combination of the maximum entropy method for spectral analysis and the non-linear least squares method for fitting analysis (Makin2, Suwa Trust, Tokyo, Japan) has recently been developed. Spectral entropy which is derived by the Memcalc method might be useful to expressing the trend of time-series behavior. AIM: Spectral entropy of ECG which is calculated with the Memcalc method was evaluated by comparing to the PSG results. SUBJECTS: Obstructive SAS patients (n = 79) and control volanteer (n = 7) METHODS: ECG was recorded using MemCalc-Makin2 (GMS) with PSG recording using Alice IV (Respironics) from 20:00 to 6:00. Spectral entropy of ECG, which was calculated every 2 seconds using the Memcalc method, was compared to sleep stages which were analyzed manually from PSG recordings. RESULTS: Spectral entropy value (-0.473 vs. -0.418, p < 0.05) were significantly increased in the OSAHS compared to the control. For the entropy cutoff level of -0.423, sensitivity and specificity for OSAHS were 86.1% and 71.4%, respectively, resulting in a receiver operating characteristic with an area under the curve of 0.837. The absolute value of entropy had inverse correlation with stage 3. CONCLUSIONS: Spectral entropy, which was calculated with Memcalc method, might be a possible index evaluating the quality of sleep.

P- and R-type Ca2+ channels regulating spinal glycinergic nerve terminals.

The contributions of P- and R-type Ca2+ channels on glycinergic nerve endings (boutons) projecting to the rat spinal sacral commissural nucleus (SDCN) neurons are not understood. Thus, we investigated the functional role of P- and R-type Ca2+ channels by measuring the inhibitory postsynaptic currents (eIPSCs) evoked from individual nerve endings (boutons) by focal electrical stimulation. The current amplitude and failure rate (Rf) of glycinergic eIPSCs varied directly with changes in [Ca2+](o). Low concentration of omega-Aga IVA (P-type selective antagonist) suppressed eIPSCs as much as high concentration (both P- and Q-type selective) indicating little contribution of Q-type Ca2+ channels. Antagonism of R-type Ca2+ channels with SNX-482 and Ni2+ greatly decreased the current amplitude and increased failure rate (Rf) of glycinergic eIPSCs. Overall, our results suggest that the dominant control of glycine release depends on Ca2+ entry through P- and R-type Ca2+ channels that ubiquitously populate spinal glycine release sites.

A retinal circuit model accounting for wide-field amacrine cells.

In previous experimental studies on the visual processing in vertebrates, higher-order visual functions such as the object segregation from background were found even in the retinal stage. Previously, the "linear-nonlinear" (LN) cascade models have been applied to the retinal circuit, and succeeded to describe the input-output dynamics for certain parts of the circuit, e.g., the receptive field of the outer retinal neurons. And recently, some abstract models composed of LN cascades as the circuit elements could explain the higher-order retinal functions. However, in such a model, each class of retinal neurons is mostly omitted and thus, how those neurons play roles in the visual computations cannot be explored. Here, we present a spatio-temporal computational model of the vertebrate retina, based on the response function for each class of retinal neurons and on the anatomical inter-cellular connections. This model was capable of not only reproducing the spatio-temporal filtering properties of the outer retinal neurons, but also realizing the object segregation mechanism in the inner retinal circuit involving the "wide-field" amacrine cells. Moreover, the first-order Wiener kernels calculated for the neurons in our model showed a reasonable fit to the kernels previously measured in the real retinal neuron in situ.

Differential effects of divalent cations on spontaneous and evoked glycine release from spinal interneurons.

The effects of Ca2+, Sr2+, and Ba2+ on spontaneous and evoked glycinergic inhibitory postsynaptic currents (mIPSCs and eIPSCs) were studied using the "synaptic bouton" preparation of rat spinal neurons and conventional whole cell recording under voltage-clamp conditions. In response to application of Ca2+-free solution, the frequency of mIPSC initially rapidly decreased to 40 approximately 50% of control followed by a gradual further decline in mIPSC frequency to approximately 30% of control. Once mIPSC frequency had significantly decreased in Ca2+-free solution, application of Ca2+, Sr2+, or Ba2+ increased mIPSC frequency. The rank order of effect in restoring mIPSCs was Ba2+>>Ca2+>Sr2+. Moreover, the application of excess external [K+]o solution (30 mM) containing Sr2+ or Ba2+ after 2 h in Ca2+-free solution also increased mIPSC frequency in the order Sr2+>or==Ba2+>Ca2+. The mean mIPSC amplitude was not affected at all. In contrast, eIPSCs produced by focal stimulation of single boutons were completely abolished in Ca2+-free solution or when Ca2+ was replaced by Sr2+ or Ba2+ (2 mM each). However, eIPSCs were restored in increased concentrations of Sr2+ or Ba2+ (5 mM each). The results show that these divalent cations affect mIPSC and eIPSCs differently and indicate that the mechanisms underlying transmitter release that generates eIPSCs and mIPSC in presynaptic nerve terminals are different. The different mechanisms might be explained by the different sensitivity of synaptotagmin isoforms to Ca2+, Sr2+, and Ba2+.

[Staging of sleep based on electroencephalograms and mental electromyograms recorded by a simplified polygraph, MemCalc-Malkin2].

OBJECTIVE: To examine the feasibility of MemCalc-Malkin2, a simplified polygraph, for staging of sleep. DESIGN: Electroencephalograms and mentalelectromyograms were recorded in 33 patients with possible obstructive sleep apnea-hypopnea syndrome by a simplified polygraph, MemCalc-Malkin2, and their frequencies were analyzed according to the sleep stage that were determined by a simultaneous conventional polysomnography. RESULTS: Sleep was divided into four stages, i.e., awake(SWake), rapid eye movement phase(SREM), shallow non-REM sleep {S(1+2)}, and deep non-REM sleep {S(3+4)}. The ratio of the amount of beta waves to that of delta waves was significantly different between the four sleep stages (p < 0.05), being highest in SWake and lowest in S(3+4). Mental electromyographic discharges were significantly more active in SWake and S(1+2) than in S(3+4) and SREM. CONCLUSION: A MemCalc-Malkin2 appears promising for staging of sleep.

Parallel inhibition of cortico-muscular synchronization and cortico-spinal excitability by theta burst TMS in humans.

OBJECTIVE: To investigate the after-effects of theta burst TMS (TBS) on cortico-muscular synchronization, and on cortico-spinal excitability, in humans. METHODS: We studied 10 healthy subjects using a continuous paradigm of TBS (cTBS), i.e. 600 pulses in 40s. Before and after the cTBS, coherence function was computed as a measure of cortico-muscular synchronization by recording electroencephalogram (EEG) from 19 scalp sites and electromyogram (EMG) from right first dorsal interosseous (FDI) muscle during the isometric contraction. In a separate experiment, motor-evoked potentials (MEPs) in response to single TMS pulses were recorded from the FDI muscle before and after the cTBS, to measure cortico-spinal excitability. RESULTS: When the cTBS was applied over the left primary motor cortex (M1), the beta-band cortico-muscular coherence for the C3 scalp site, as well as the MEP amplitude significantly decreased in 30-60 min, and then recovered to the original levels in 90-120 min. Neither sham stimulation nor cTBS applied over 2 cm posterior to M1 produced significant effects. CONCLUSIONS: cTBS-over-M1 can inhibit the cortico-muscular synchronization in parallel with the decline of cortico-spinal excitability. SIGNIFICANCE: Our results provide the first evidence that TBS can efficiently alter the functional cortico-muscular coupling in humans.

A comparison of urinary albumin-total protein ratio to phase-contrast microscopic examination of urine sediment for differentiating glomerular and nonglomerular bleeding.

BACKGROUND: Hematuria can be classified as either glomerular or nonglomerular, depending on the bleeding source. We recently reported that urinary albumin-total protein ratio is potentially useful for identifying the source of hematuria. STUDY DESIGN: Diagnostic test study. SETTING & PARTICIPANTS: 579 fresh urine specimens with microhematuria (> or =5 red blood cells/high-power field) collected from patients with the source of the hematuria confirmed on histopathologic and/or imaging studies and clinical criteria assessed. INDEX TEST: Each urine specimen was evaluated morphologically by using phase-contrast microscopy and biochemically by using urinary albumin-total protein ratio, albumin-creatinine ratio, and total protein-creatinine ratio. REFERENCE TEST: Each patient had a definitive clinical diagnosis established by means of biopsy (64.4%), imaging studies (21.2%), and routine optimal microscopic examination of urine sediment (14.3%). RESULTS: Of 579 specimens, 329 were obtained from patients with glomerular disease and 250 were obtained from patients with nonglomerular disease. Mean urinary albumin-total protein, albumin-creatinine, and total protein-creatinine ratios for those with glomerular versus nonglomerular diseases were 0.73 +/- 0.11 versus 0.41 +/- 0.14 mg/mg (P < 0.001), 1,110 +/- 1,850 versus 220 +/- 560 mg/g (P < 0.001), and 1,600 +/- 3,010 versus 480 +/- 1,160 mg/g (P < 0.001), respectively. The percentage of patients with greater than 3% glomerular red cells was 83.3% versus 24.8% (P < 0.001). Receiver operating characteristic curve analysis showed that areas under the curve for albumin-total protein ratio, albumin-creatinine ratio, and total protein-creatinine ratio were 0.992, 0.781, and 0.688, respectively (P < 0.001, albumin-total protein versus albumin-creatinine; P < 0.001, albumin-total protein versus total protein-creatinine). At cutoff values of 0.59 mg/mg, 71 mg/g, and 265 mg/g, albumin-total protein ratio, albumin-creatinine ratio, and total protein-creatinine ratio had sensitivities and specificities of 97.3% and 100%, 78.9% and 61.1%, and 68.8% and 62.0% for detecting glomerular disease, respectively. Phase-contrast microscopy had sensitivity of 83.3% and specificity of 75.2% for detecting glomerular disease. LIMITATIONS: Albumin-total protein ratio cannot be used in patients with urinary total protein less than 5 mg/dL (<0.05 g/L). Use of only 1 sample from 1 patient may not be sufficient to obtain definitive results. CONCLUSIONS: Urinary albumin-total protein ratio is much more useful than phase-contrast microscopy for differentiating between glomerular and nonglomerular disease in patients with microscopic hematuria.

Effects of various K+ channel blockers on spontaneous glycine release at rat spinal neurons.

Molecular biology approaches have identified more than 70 different K+ channel genes that assemble to form diverse functional classes of K+ channels. Although functional K+ channels are present within presynaptic nerve endings, direct studies of their precise identity and function have been generally limited to large, specialized presynaptic terminals such as basket cell terminals and Calyx of Held. In the present study, therefore, we investigated the functional K+ channel subtypes on the small glycinergic nerve endings (< 1 microm diameter) projecting to spinal sacral dorsal commissural nucleus (SDCN) neurons. In the presence of TTX, whole-cell patch recording of mIPSCs was made from mechanically dispersed SDCN neurons in which functional nerve endings remain attached. Glycinergic responses were isolated by blocking glutamatergic and GABAergic inputs with CNQX, AP5 and bicuculline. The K+ channel blockers, 4-AP, TEA, delta-dendrotoxin, margatoxin, iberiotoxin, charybdotoxin and apamin, significantly increased 'spontaneous' mIPSC frequency without affecting mIPSC amplitude. The results suggest the existence of the following K+ channel subtypes on glycinergic nerve endings that are involved in regulating 'spontaneous' glycine release (mIPSCs): the Shaker-related K+ channels Kv1.1, Kv1.2, Kv1.3, Kv1.6 and Kv1.7 and the intracellular Ca2+ -sensitive K+ channels BKCa, IKCa and SKCa. Ca2+ channel blockers by themselves, including L-type (nifedipine), P/Q-type (omega-agatoxin IVA, AgTX) and N-type (omega-conotoxin GVIA, CgTX), did not alter the 'spontaneous' mIPSC frequency or amplitude, but inhibited the increase of the mIPSC frequency evoked by 4-AP, indicating the participation of L-, P/Q- and N-type Ca2+ channels regulating 'spontaneous' glycine release from the nerve terminals.

Effects of concurrent visual tasks on cortico-muscular synchronization in humans.

To study the effects of external visual stimulation on motor cortex-muscle synchronization, coherence between electroencephalography (EEG) and electromyography (EMG) was measured in normal subjects under Before, Task (visual task: Ignore or Count, or arithmetic task) and After conditions. The control (Before and After) conditions required the subject to maintain first dorsal interosseous muscle contraction without visual stimulation. In the visual task, a random series of visual stimuli were displayed on a screen while the subjects maintained the muscle contraction. The subjects were asked to ignore the stimuli in the Ignore condition and to count certain stimuli in the Count condition. Also, in the arithmetic task, the subjects were asked to perform a simple subtraction. The EEG-EMG coherence found at C(3) site at 13-30 Hz (beta) was increased and sustained in magnitude during the Ignore and Count conditions, respectively. To examine the cause of the change of coherence, changes of EEG and EMG spectral power were computed for each frequency band. There was little change in the EMG spectral power in any frequency bands. While the spectral power of EEG unchanged in the beta band, it significantly increased and decreased in the range of 8-12 Hz and of 31-50 Hz, respectively, for both Ignore and Count conditions, not only at the C(3) site but at various sites as well. These results were in contrast to those obtained for the arithmetic task: the beta band EEG-EMG coherence was attenuated and the EEG spectral power at 4-7 Hz and at 31-50 Hz were significantly increased and decreased, respectively. As a conclusion, the present results are consistent with the idea that the enhanced 8-12 Hz/decreased 31-50 Hz oscillations affect strength of the beta band cortico-muscular synchronization by suppressing the visual processing.

Effect of theta burst stimulation over the human sensorimotor cortex on motor and somatosensory evoked potentials.

OBJECTIVE: To study the after-effect of theta burst stimulation (TBS) over the left sensorimotor cortex on the size of somatosensory as well as motor evoked potentials evoked from both hemispheres in healthy human subjects. METHODS: We used a continuous TBS paradigm for 40 s (600 pulses) in which a burst of 3 transcranial magnetic stimuli at 50 Hz is repeated at 5 Hz [Huang YZ, Edwards MJ, Rounis E, Bhatia KP, Rothwell JC. Theta burst stimulation of the human motor cortex. Neuron 2005;45:201-6]. Somatosensory evoked potentials (SEPs) following electrical stimulation of right or left median nerve and motor evoked potentials (MEPs) in the right or left first dorsal interosseous (FDI) muscles were recorded before and after TBS over the left motor cortex (M1) or a point 2 cm posterior to left M1. RESULTS: Amplitudes of P25/N33 (parietal components) following right median nerve stimulation were significantly increased for at least 53 min after TBS over the left M1, whereas this component was suppressed for 13 min after TBS over a point 2 cm posterior. MEPs in right as well as left FDI muscles were suppressed with a similar time course after TBS over the left M1. CONCLUSIONS: A single-session of TBS over the sensorimotor cortex can induce a short-lasting change in the size of ipsilateral cortical components of SEPs as well as MEPs evoked from both hemispheres. SIGNIFICANCE: TBS is an interventional tool that can induce rapid reorganization within cortical somatosensory as well as motor networks in humans.