The changes of evoked electromyogram and somatosensory evoked potential with discriminative reaction task / 体力科学

The somatosensory evoked potential (SEP) is attenuated (gating) and the spinal motoneuron pool is facilitated before and during movement. However, the relationship between these changes has not been elucidated. In the present study, the SEP and the evoked electromyogram were simultaneously recorded during a discriminative reaction task in seven healthy subjects. Electrical stimulation applied to the posterior tibial nerve in the popliteal fossa was used as a response signal. The experimental condition were: 1) full relaxation and no response to either right or left stimulation (Control) ; 2) no response to right stimulation and quick contraction of right ankle with left stimulation (L-R) ; 3) no response to left stimulation and quick contraction of right ankle with right stimulation (R-R) . Right and left legs were randomly stimulated under each condition. The H-response gains of the right leg with movement were significantly facilitated compared to the left leg without movement in L-R and R-R conditions. The results indicated that movement enhanced the motoneuron excitability regardless of sensory concentration. In the L-R condition, N 40 at Cz evoked by left operative stimulation that produced right leg movement was significantly increased. However, in the R-R condition, it was significantly attenuated when it was recorded by right operative stimulation that produced right leg movement. These results indicated that concentration on the operative stimulation enhanced the N 40 gain and it reflected the concentration on sensory information, but simultaneously induced the movement, and its gain was strongly controlled by the motor system.

RELATIONSHP BETWEEN OXYGENATION AND MYOELECTRIC ACTIVITY AT VASTUS LATERALIS AND LATERAL GASTROCNEMIUS MUSCLES / 体力科学

In order to find the cause behind the difference in the pattern of oxygenation between thigh and calf muscles during an incremental cycling exercise, we investigated the relationship between oxygenation and surface myoelectric activity. Five healthy male subjects performed the five 6-min cycling exercises of 50, 100, 150, 200 and 250 watts. We measured oxygenated hemoglobin/myoglobin (oxy-Hb/Mb) on continuous wave near infrared spectroscopy (NIR) and myoelectric activity with surface electrodes (EMG) . The NIR probe and electrodes were positioned on the vastus lateralis muscle (VL) and lateral gastrocnemius muscle (LG) of the right leg. The relative change in oxy-Hb/Mb was estimated by regarding the oxy-Hb/Mb level in the resting condition as 100% and that obtained during thigh occlusion as 0 %. The mean values of oxy-Hb/Mb and integrated EMG (iEMG) determined ranged from 5'30'' to 6'00'' at each work rate. In the VL, the oxy-Hb/Mb level decreased slightly at 50 and 150 watts (99.2±6.8% and 84.6±12.9%), followed by a more prom-inent decrease at 200 and 250 watts (74.9±11.9 and 65.2±9.6%) . The iEMG increased slowly at 50 and 150 watts (24.9±8.8 and 38.0±8.8μV), and a rapid increment occurred at 200 and 250 watts (49.6±13.0 and 57.3±19.6μV) . In the LG, however, the oxy-Hb/Mb level was decreased slightly at 50 and 200 watts (97.3±11.1 and 87.4±6.4%) and a rapid decrement occurred at 250 watts (74.1±6.0%) . The iEMG increased slowly at 50 and 200 watts (18.3±9.4 and 30.5±8.8 μV), and a rapid increment occurred at 250 watts (38.5±8.9 μV) . There was a significant negative correlation between the oxy-Hb/Mb level and iEMG in the VL (r=-0.587, p<0.001) and in the LG (r=-0.599, p<0.001) . From these results, we speculated that the difference in the relative change of oxy-Hb/Mb between the vastus lateralis and the lateral gastrocnemius muscle was due to the difference of increase pattern of muscle activity accompanied by an increase in exercise intensity in these two muscles.

Systolic blood pressure responses to pedalling exercise / 体力科学

The response of systolic blood pressure (SBP) to pedalling exercise was studied in 32 healthy young men. The subjects performed the exercise at different intensities for 3 min using an incremental loading method. The first work load was 30W and increased by 30W until the heart rate (HR) reached about 170 bpm. SBP at HR 100. 160 bpm (SBP@HR 100-160) was calculated from the cubic regression equation in each subject. Mean SBP and SEM at HR 100, 110, 120, 130, 140, 150, 160 were 143.9 (2.49), 152.9 (2.79), 161.6 (3.02), 170.0 (3.16), 177.8 (3.25), 184.5 (3.34), and 189.7 (3.45) mmHg, respectively. However, the rate of elevation of SBP was zero at HR 175 bpm, which was calculated from the cubic regression equation. This may indicate that SBP is inhibited by baroreceptors and other factors at HR above 170 bpm. There were no significant relationships between SBPs@HR 100-160 and indices of aerobic capacity such as maximal oxygen consumption or PWC 170. Double product (DP) as an index of oxygen consumption by cardiac muscle increased with HR without any reduction in its rate of elevation during exercise.

Scalp distribution of movemnt-associated cerebral potentials preceding voluntarily, self-paced movement / 体力科学

The view which movement-associated cerebral potentials preceding voluntarily, self-paced movement are recorded through the human scalp is well known at present. Then, it is the focus of the present study that what functional significance of each component is. However, the present study reports of N 1 potential constituting movement-associated cerebral potentials were almost based on data of right handedness. Therefore, the authors thought that only data obtained from right-handedness are inadequate because of elucidating in more detail functional significance.<BR>The purpose of present study was intended to investigate functional significance of N 1 potential through the comparison between the distribution over the scalp of N 1 potential of right-handedness and left-handedness.<BR>The following results were obtained;<BR>1) The amplitude of N 1 potential preceding voluntary right hand movement in case of right-handedness showed predominantly high tendency at Cz, C3 and also, showed high tendency at Cz, C3 in case of left-handedness. But, N1 potential of left-handedness did not show more significant tendency at Cz, C3 than right-handedness in voluntary right movement.<BR>2) The amplitude of N1 potential preceding voluntary left hand movement showed high tendency at Cz, C4 in case of right-handedness. But, in case of left-handedness, there were the cases that the amplitude of N1 potential showed high tendency at Cz, C4 and did not show.<BR>3) The amplitude of N1 potential preceding voluntary bilateral simultaneous movement showed high tendency at Cz, C3 in case of righ-handedness and showed clear asymmetry. In case of left-handedness, there were two types of subjects who showed asymmetry and not.<BR>From the results described above, the authors may conclude that the findings which N1 potential shows preponderance over the hemisphere contralateral to the moving limb are based persistently on data of right-handedness and would not be able to apply to data of left-handedness. However, the results of the present experiment were applied to subjects assessed by assesment criterion of dominant and none-dominant hand described in“EXPERIMENT METHOD”and there was the limit of the present experiment in the assessment method of dominant and none-dominant hand.

A STUDY ON DELAY AND QUICKNESS OF SENSORY-MOTOR INTEGRATION PROCESS / 体力科学

Nishihira and Araki grasped the living body as sensory-motor system, and thought negative potential appearing 25 msec after stimulus of S. S. C. P. as potential arriving at the first sensory area and speculated potential appearing 50-56 msec in advance of muscle discharges as being integrated of motor cortex neurones in the present experiment.<BR>Therefore, the purpose of the present experiment is to investigate the hypothesis that delay and quickness of reaction movement execution depends on delay and quickness of transaction process between sensory and motor area and, also, to identify the distribution over the scalp of motor potential.<BR>The present experiment gave the following results.<BR>1. As for the distribution over the scalp of motor potential, the amplitude of motor potential at Cz showed maximum in case of the left hand reaction movement to right median nerve stimulus. however, comparing the amplitude of motor potenital at C4 with at C3, the amplitude of motor potential at C4 was higher than at C3.<BR>Comparing the amplitude of motor potential at C3 with at C4 except for at Cz, the amplitude of motor potential at C3 was higher than at C4 in case of the right hand reaction movement to right median nerve stimulus.<BR>2. Investigating correlation between reaction time and sensory-motor integration time at C3, C2, C4, there was a higher correlation.<BR>3. Correlation between reaction time and the amplitude of CNV at C2 showed inverse proportion. In addition to, correlation between reaction time and appearance latency of CNV was obscure.

RELATIONSHIP BETWEEN ALPHA-BLOCKING AND SLOW POTENTIAL CHANGES PRECEDING REACTION MOVEMENT / 体力科学

In order to investigate the association of alpha-blocking with motor set under the condition of simple reaction movement, the scalp distribution of alpha wave envelope recorded by averaging method was compared with that of slow potential changes. The results were as follows.<BR>1) The slow potential changes (readiness potential, early and late component of CNV) were large over the central and frontal area. The readiness potential was larger over the contralateral than the ipsilateral central motor area, while the early component of CNV showed bilateral spread. The late component of CNV showed the similar scalp distribution to that of readiness potential, but the latter was much more lateralized.<BR>2) The alpha-blocking was bilaterally symmetrical over the central and occipital area under the condition of photic stimulus without movement. But the alpha-blocking accompanying preparatory signal increased over the frontal and central area compared with control alpha-blocking, and was larger over the contralateral than ipsilateral central motor area.<BR>3) The maximal alpha-blocking rate showed to correlate negatively with its latency under each condition. The difference in alpha-blocking rate at the onset of the imperative stimulus between reaction movement and control showed to correlate negatively with reaction time.<BR>From these findings, it seems that alpha-blocking accompanying preparatory signal reflects not only input system but also readiness potential component, and that in temporal respect alpha-blocking increases at the onset of movement.

MOVEMENT-ASSOCIATED CORTICAL POTENTIAL PRECEDING VOLUNTARY MOVEMENT / 体力科学

The purpose of the present experiment is to identify, in detail, results of the preceding experiment of authors that the amplitude of N<SUB>1</SUB> potential was dominant over motor cortex area contralateral to moving limb, with bipolar lead and is to investigate negative potential appearing the scalp preceding voluntary movement depends on a precaution stimulus or on readiness of movement execution only.<BR>In addition to, discussing' the difference of CNV (Contingent Negative Variation) and N<SUB>1</SUB> potential is, also, the purpose of the present experiment.<BR>The present experiment gave the following results.<BR>1. The results obtained with monopolar lead were that the amplitude of N<SUB>1</SUB> potential was maximal at lead placement Cz in all movement.<BR>2. The results obtained with bipolar lead were that the amplitude of N<SUB>1</SUB> potential showed, relatively, lower tendency in the combination within central area and showed, relatively, higher tendency in the combination of other lead placement to central area.<BR>3. Judging from all the scalp, the amplitude of N<SUB>1</SUB> potential showed high tendency at central area.<BR>4. In particular, clear difference was identified between the latency of CNV and that of N<SUB>1</SUB> potential.<BR>5. As showing much the same amplitude except for lead placement Cz, CNV extended from central area over the scalp.