Mineo Oyama

EMG-angle relationship of the hamstring muscles during maximum knee flexion

The aim of the present study was to investigate the EMG-joint angle relationship during voluntary contraction with maximum effort and the differences in activity among three hamstring muscles during knee flexion. Ten healthy subjects performed maximum voluntary isometric and isokinetic knee flexion. The isometric tests were performed for 5 s at knee angles of 60 and 90 degrees. The isokinetic test, which consisted of knee flexion from 0 to 120 degrees in the prone position, was performed at an angular velocity of 30 degrees /s (0.523 rad/s). The knee flexion torque was measured using a KIN-COM isokinetic dynamometer. The individual EMG activity of the hamstrings, i.e. the semitendinosus, semimembranosus, long head of the biceps femoris and short head of the biceps femoris muscles, was detected using a bipolar fine wire electrode. With isometric testing, the knee flexion torque at 60 degrees knee flexion was greater than that at 90 degrees. The mean peak isokinetic torque occurred from 15 to 30 degrees knee flexion angle and then the torque decreased as the knee angle increased (p<0.01). The EMG activity of the hamstring muscles varied with the change in knee flexion angle except for the short head of the biceps femoris muscle under isometric condition. With isometric contraction, the integrated EMGs of the semitendinosus and semimembranosus muscles at a knee flexion angle of 60 degrees were significantly lower than that at 90 degrees. During maximum isokinetic contraction, the integrated EMGs of the semitendinosus, semimembranosus and short head of the biceps femoris muscles increased significantly as the knee angle increased from 0 to 105 degrees of knee flexion (p<0.05). On the other hand, the integrated EMG of the long head of the biceps femoris muscle at a knee angle of 60 degrees was significantly greater than that at 90 degrees knee flexion with isometric testing (p<0.01). During maximum isokinetic contraction, the integrated EMG was the greatest at a knee angle between 15 and 30 degrees, and then significantly decreased as the knee angle increased from 30 to 120 degrees (p<0.01). These results demonstrate that the EMG activity of hamstring muscles during maximum isometric and isokinetic knee flexion varies with change in muscle length or joint angle, and that the activity of the long head of the biceps femoris muscle differs considerably from the other three heads of hamstrings.

Transcranial direct current stimulation over the motor association cortex induces plastic changes in ipsilateral primary motor and somatosensory cortices

OBJECTIVE This study was performed to elucidate whether transcranial direct current stimulation (tDCS) over the motor association cortex modifies the excitability of primary motor (M1) and somatosensory (S1) cortices via neuronal connectivity. METHODS Anodal, cathodal, and sham tDCS (1 mA) over the left motor association cortex was applied to 10 subjects for 15 min using electrodes of two sizes (9 and 18 cm(2)). Both motor evoked potentials (MEPs) and somatosensory evoked potentials (SEPs) were recorded before, immediately after, and 15 min after tDCS. Electrode positions were confirmed by overlaying them on MRI anatomical surface images of two individuals. RESULTS After applying anodal tDCS using the large electrode, amplitudes of MEP components significantly decreased, whereas those of early SEP components (N20 and P25) increase. Opposite effects were observed on MEPs and SEPs after cathodal tDCS. However, a small electrode did not significantly influence either MEPs or SEPs, irrespective of polarity. The small electrode covered mainly the dorsal premotor cortex (PMd) while the large electrode involved the supplementary motor area (SMA) in addition to PMd. CONCLUSIONS These results suggest that anodal tDCS over PMd together with SMA enhanced the inhibitory input to M1 and excitatory input to S1, and that cathodal tDCS might lead to an opposite effect. SIGNIFICANCE The finding that only the large electrode modulated M1 and S1 implies that activation of PMd together with SMA by tDCS can induce plastic changes in primary sensorimotor areas.

Neuromagnetic activation of primary and secondary somatosensory cortex following tactile-on and tactile-off stimulation

OBJECTIVE Magnetoencephalography (MEG) recordings were performed to investigate the cortical activation following tactile-on and tactile-off stimulation. METHODS We used a 306-ch whole-head MEG system and a tactile stimulator driven by a piezoelectric actuator. Tactile stimuli were applied to the tip of right index finger. The interstimulus interval was set at 2000 ms, which included a constant stimulus of 1000 ms duration. RESULTS Prominent somatosensory evoked magnetic fields were recorded from the contralateral hemisphere at 57.5 ms and 133.0 ms after the onset of tactile-on stimulation and at 58.2 ms and 138.5 ms after the onset of tactile-off stimulation. All corresponding equivalent current dipoles (ECDs) were located in the primary somatosensory cortex (SI). Moreover, long-latency responses (168.7 ms after tactile-on stimulation, 169.8 ms after tactile-off stimulation) were detected from the ipsilateral hemisphere. The ECDs of these signals were identified in the secondary somatosensory cortex (SII). CONCLUSIONS The somatosensory evoked magnetic fields waveforms elicited by the two tactile stimuli (tactile-on and tactile-off stimuli) with a mechanical stimulator were strikingly similar. These mechanical stimuli elicited both contralateral SI and ipsilateral SII activities. SIGNIFICANCE Tactile stimulation with a mechanical stimulator provides new possibilities for experimental designs in studies of the human mechanoreceptor system.

Cortical neuromagnetic activation accompanying two types of voluntary finger extension

We examined the amplitude and latency of movement-related cerebral field (MRCF) waveforms, the generator and afferent feedback of movement-evoked field 1 (MEF1), and the relationship between motor field neuromagnetic activity and electromyographic activity during performance of two types of voluntary index extension. Eight healthy, right-handed male volunteers participated in this study. Experiments for each subject consisted of recording of MRCFs following two types of finger movement. One (Task 1) involved voluntary extension of the right index finger to about 40 degrees . In the second (Task 2), an elastic band was placed on the right index fingertip, producing a resistance of about 1.5 times the electromyographic activity associated with the voluntary movement yielding extension to approximately 40 degrees . Peak amplitude and the ECD moment of the motor field differed significantly between the two tasks. In Task 2, the electromechanical delay from EMG onset to movement onset (77.8+/-16.2) was longer than in Task 1 (44.4+/-10.4). However, the latency from EMG onset to MEF1 peak was 87.6+/-8.5 ms in Task 2, and did not differ significantly from that in Task 1 (88.6+/-8.5). The ECDs of MEF1 were located significantly medial to N20 m and lateral and posterior to the motor field. These findings suggest that the ECD of MEF1 is located in area 3b, but is slightly different from N20 m, and that this MEF1 component activation is due not to the onset of joint movement but to that of muscular contraction.

Muscle-afferent projection to the sensorimotor cortex after voluntary movement and motor-point stimulation: An MEG study

OBJECTIVE To investigate the projection of muscle afferents to the sensorimotor cortex after voluntary finger movement by using magnetoencephalography (MEG). METHODS The movement-evoked magnetic fields (MEFs) after voluntary index-finger extension were recorded by a 204-channel whole-head MEG system. Somatosensory-evoked magnetic fields (SEFs) were recorded after motor-point stimulation was applied to the right extensor indicis muscle by using a pair of wire electrodes. RESULTS The MEF waveforms were observed at 35.8±9.7 ms after movement onset (MEF1). The most concentrated SEFs were identified at 78.7±5.6 ms (M70), and the onset latency of M70 was 39.0±5.5 ms after motor-point stimulation. The mean locations of the equivalent current dipoles (ECDs) of MEF1 and M70 were significantly medial and superior to that of N20m elicited by median-nerve stimulation. The ECD locations and directions of both MEF1 and M70 were concordant in the axial, coronal and sagittal planes. CONCLUSIONS MEF1 and M70 might be elicited by muscle-afferent feedback following muscle contraction. In addition, these ECDs may be located in area 4. SIGNIFICANCE Motor-point stimulation is a useful tool for confirming the projection of muscle-afferent feedback to the sensorimotor cortex after voluntary movement.

Changes in salivary physiological stress markers induced by muscle stretching in patients with irritable bowel syndrome

BackgroundPsychophysiological processing has been reported to play a crucial role in irritable bowel syndrome (IBS) but there has been no report on modulation of the stress marker chromogranin A (CgA) resulting from muscle stretching. We hypothesized that abdominal muscle stretching as a passive operation would have a beneficial effect on a biochemical index of the activity of the sympathetic/adrenomedullary system (salivary CgA) and anxiety.MethodsFifteen control and eighteen untreated IBS subjects underwent experimental abdominal muscle stretching for 4 min. Subjects relaxed in a supine position with their knees fully flexed while their pelvic and trunk rotation was passively and slowly moved from 0 degrees of abdominal rotation to about 90 degrees or the point where the subject reported feeling discomfort.Changes in the Gastrointestinal Symptoms Rating Scale (GSRS), State Trait Anxiety Inventory (STAI), Self-rating Depression Scale (SDS), ordinate scale and salivary CgA levels were compared between controls and IBS subjects before and after stretching. A three-factor analysis of variance (ANOVA) with period (before vs. after) as the within-subject factor and group (IBS vs. Control), and sex (men vs. female) as the between-subject factors was carried out on salivary CgA.ResultsCgA showed significant interactions between period and groups (F[1, 31] = 4.89, p = 0.03), and between groups and sex (F[1, 31] = 4.73, p = 0.03). Interactions between period and sex of CgA secretion were not shown (F[1, 3] = 2.60, p = 0.12). At the baseline, salivary CgA in IBS subjects (36.7 ± 5.9 pmol/mg) was significantly higher than in controls (19.9 ± 5.5 pmol/mg, p < 0.05). After the stretching, salivary CgA significantly decreased in the IBS group (25.5 ± 4.5 pmol/mg), and this value did not differ from that in controls (18.6 ± 3.9 pmol/mg).ConclusionOur results suggest the possibility of improving IBS pathophysiology by passive abdominal muscle stretching as indicated by CgA, a biochemical index of the activity of the sympathetic/adrenomedullary system.

Motor Cortex-Evoked Activity in Reciprocal Muscles Is Modulated by Reward Probability

Horizontal intracortical projections for agonist and antagonist muscles exist in the primary motor cortex (M1), and reward may induce a reinforcement of transmission efficiency of intracortical circuits. We investigated reward-induced change in M1 excitability for agonist and antagonist muscles. Participants were 8 healthy volunteers. Probabilistic reward tasks comprised 3 conditions of 30 trials each: 30 trials contained 10% reward, 30 trials contained 50% reward, and 30 trials contained 90% reward. Each trial began with a cue (red fixation cross), followed by blue circle for 1 s. The subjects were instructed to perform wrist flexion and press a button with the dorsal aspect of middle finger phalanx as quickly as possible in response to disappearance of the blue circle without looking at their hand or the button. Two seconds after the button press, reward/non-reward stimulus was randomly presented for 2-s duration. The reward stimulus was a picture of Japanese 10-yen coin, and each subject received monetary reward at the end of experiment. Subjects were not informed of the reward probabilities. We delivered transcranial magnetic stimulation of the left M1 at the midpoint between center of gravities of agonist flexor carpi radialis (FCR) and antagonist extensor carpi radialis (ECR) muscles at 2 s after the red fixation cross and 1 s after the reward/non-reward stimuli. Relative motor evoked potential (MEP) amplitudes at 2 s after the red fixation cross were significantly higher for 10% reward probability than for 90% reward probability, whereas relative MEP amplitudes at 1 s after reward/non-reward stimuli were significantly higher for 90% reward probability than for 10% and 50% reward probabilities. These results implied that reward could affect the horizontal intracortical projections in M1 for agonist and antagonist muscles, and M1 excitability including the reward-related circuit before and after reward stimulus could be differently altered by reward probability.

P20-11 Transcranial direct current stimulation over the motor association cortex induces plastic changes in the ipsilateral sensory-motor cortices

(ipsilateral BST), and that between the inion and the left mastoid process (contralateral BST). We first performed inion BST to evoke approximately 1.0 mV MEP, then the other two BSTs using the same stimulus intensity. In 25 out of the 32 subjects, active motor thresholds (AMTs) of the BSTs were also compared. Results: The contralateral BST was not the most effective stimulation method in any of the subjects. According to the MEP amplitude, the ipsilateral BST elicited larger MEPs than the inion BST in 19 subjects (60%). In the other 12 subjects, the inion BST produced larger MEPs. AMT for the ipsilateral BST was lower than that for the inion BST in 14 out of the 25 subjects (56%). On the other hand, seven subjects had lower AMT for inion BST than for ipsilateral BST. In the other four subjects, AMT was the same for inion and ipsilateral BST. The data on the amplitude and AMT were consistent; that is, in those who showed lower AMT for ipsilateral BST (14 subjects), larger MEPs were elicited by the ipsilateral BST. Out of the four subjects who had the same AMT, MEPs to ipsilateral BST were larger in two subjects. Conclusions: In more than half of the subjects, ipsilateral BST produced the largest MEPs and had lower AMT than inion BST. Significance: The stimulation site for BST should be searched before we obtain MEPs to BST in central motor conduction studies.

Time-dependent changes in the structure of calcified fibrocartilage in the rat Achilles tendon–bone interface with sciatic denervation

The enthesis transmits a physiological load from soft to hard tissue via fibrocartilage. The histological alterations induced by this physiological loading remain unclear. This study was performed to examine the histomorphological alterations in the collagen fiber bundle alignment and depth of collagen interdigitation between the calcified fibrocartilage and the bone. We examined the Achilles enthesis of rats with sciatic denervation to explore the mechanical effects of structural changes in the enthesis. The parallelism of the collagen fiber bundles was significantly reduced 8 weeks after denervation. However, the depth of collagen interdigitation significantly increased at 2 and 4 weeks after denervation and then significantly decreased 8 weeks after denervation. In conclusion, a lack of muscle loading induced structural alterations in the distal calcified fibrocartilage. These findings suggest that while structural changes in the enthesis are necessary for the development of physiological loading, structural deformities are required in the long term. Anat Rec, 300:2166–2174, 2017.

S18.3 Cortical neuromagnetic activation following passive and active finger movement

Introduction: Our experimental goal is to examine the sensory feedback from periphery following voluntary movement. We have reported that the first component of the movement evoked cortical magnetic fields (MEF) was due not to joint movement but to that of muscular contraction (Clin Neurophysiol, 2010). However, the reasons of the long latency after electromyographic onset are not fully understood. Objectives: MEG study with passive finger movement was performed to investigate the neural mechanisms following voluntary finger movement. Methods: Six healthy male subjects (mean age 36.5±8.9 years) participated in this study. All subjects had given their written informed consent, and the study was approved by the ethics committee at our university. For MEG measurement, we used a 306 ch whole-head MEG system (Neuromag, Elekta, Finland). MEG signals were sampled at 1000 Hz with band-pass filtering from 0.03 to 330 Hz. All participants performed voluntary index extension to record the movement related cortical magnetic fields (MRCFs) and were underwent passive index extension to record the somatosensory evoked magnetic fields (SEFs). The sources of the components of interest in the MEF and SEF were estimated as the equivalent current dipoles (ECD). Results: We clearly confirmed the MRCF and SEF waveforms at the sensorimotor area contralateral to the movement in all subjects. The most prominent MRCF waveform was MEF1, which was observed at 30.1±4.8 ms after movement onset. On the other hand, the most concentrated SEF peak was identified at 37.6±8.0 ms after the onset of passive movement. The mean ECD locations for MEF1 were significantly medial to N20m after median nerve stimulation. However, the ECD locations of the first component after passive movement were very similar to the N20m. Conclusions: The MEF1 after voluntary movement were different response from the first component following passive movement in location of the ECDs. These results suggest that MEF1 was not elicited by the cutaneous receptor or joint receptor.