We investigated the effects on visual evoked potential (VEP) of stimulus configuration, interval and duration of visual stimulation using a shutter-goggle. Subjects were 13 healthy young adults. We used a vertical stripe image as the visual stimulus, which was induced by opening the shutter. The stimulus conditions were set as follows: the stripe width at 1-degree increments from 1- to 8-degree, the stimulation duration at 10-ms increments from 20- to 60-ms, and the stimulation interval at 200-ms increments from 400- to 2000-ms. In the VEP, a positive peak component (P100) was detected at 70-130 ms after shutter opening onset. P100 amplitude was significantly larger for 1- and 2-degree widths than for the other widths. The amplitude showed no significant difference between 1- and 2-degree widths, and gradually decreased from 3- to 8-degree. The amplitude was significantly smaller for 20-ms duration than for the other durations, and showed no significant difference among durations from 30- to 60-ms. The amplitude was significantly smaller for the 600-ms interval than for larger intervals, and showed no significant difference among intervals from 1000- to 2000-ms.
Gripping force depends on wrist position and was requires co-contraction of forearm flexors and extensors. Especially, the activation of forearm extensors is important for stabilization of the wrist. Therefore, the purpose of this study was to investigate whether wrist extension training without gripping motion would change gripping force-wrist angle curve and forearm muscle activation during gripping. 12 healthy subjects participated in this study. Grip strength with maximal effort and EMG of six forearm muscles (FCR, FCU, FDS, ECR, ECU and EDC) from 70 degrees flexion to 80 degrees extension at wrist were measured simultaneously at baseline and 4 weeks after training. The training was isometric wrist extension without gripping motion, which consisted of 30 repetitions equal to 70%MVC for 4 weeks (5/wk). Wrist angle at maximal gripping force was calculated from the relationship between the wrist angle and grip strength. The data investigated the training effects on grip strength and EMG activation, and the gain in wrist flexion or extension. Wrist extension force and grip strength increased significantly. But, wrist angle at maximal grip strength did not change. EMG activation of flexors did not change, but that of extensors increased significantly after training. And gain of grip strength and EMG activation of extensors in flexion range was larger than that in extension range. Wrist extension training without gripping force leads to an increase in grip strength; therefore this training program used in this study would be an effective training strategy for increasing grip strength.
In the present study, we attempted to clarify the brain activity during timely reaction and non-timely reaction by using coincidence-anticipation timing tasks that involved a downward moving visual target. The subjects were ten, healthy, right-handed adults. The tasks were displayed on a computer screen. Electrodes were placed at 128 sites on the subjects' scalp, and electroencephalograms (EEGs) were recorded. The EEGs were analyzed by fast Fourier Transform (FFT) analysis, and the percentage of beta band (13-30 Hz) at 3-30 Hz was derived from FFT analysis for each visible section, first half of the masking section and second half of the masking section. The data were divided into timely reaction and non-timely reaction groups, and the outcomes for the three sections were compared between the groups by analysis of variance.
The results showed that the percentage of beta band at 3-30 Hz increased significantly at the central region in the first half of the masking section, and at the posterotemporal's in the second half of the task. The results suggested that in the first half of the masking section, the central region activity contributed to the translation of visual information to movement prediction of visual target and in the second half of the task, error in visual information and movement prediction of visual target measurement by posterotemporal's activity in order to timely reaction in a coincidence-anticipation timing task using a downward moving visual target.
We examined the beta band patterns in an electroencephalogram, which reflects the cortical activity and information processing, during rest (Control Task: CT) and a simple reaction task (SRT) before and after a brief period of high-intensity exercise.
Twelve healthy male subjects were 6 healthy men. All participants performed an all-out running task for a brief period. The CT consisted of gazing at a fixed point for 5 minutes. The SRT was performed using a visual stimulus of a 6 points star. The electroencephalogram, recorded from the scalp for 128 channels, was filtered through 3-30 Hz bandpass, fast Fourier transform (FFT)-processed, and separated into the beta 1 and beta 2 bands. The reaction time and distribution of both bands measured on each electrode were compared for values before and after the exercise.
For the CT, the post-exercise distribution of the beta 1 band increased in all cortical regions, while that of the beta 2 band increased in the posterior temporal and visual regions. For the SRT, the post-exercise reaction time was higher than the pre-exercise value and the post-exercise distribution of the beta 1 band increased in the left temporal region.
These results suggest that all regions of the cerebral cortex in CT are activated by high-intensity exercise for a brief period. Our results indicate that the beta 1 band activity reflects information processing in the cerebral cortex and that in the SRT the left temporal region was activated by a brief period of high-intensity exercise.
We investigated activation patterns of postural muscles during bilateral-arm flexion in children. Subjects comprised healthy 14 boys and 11 girls aged 6 years. In response to a visual stimulus presented at 1-3 s after a warning signal, the subjects initiated bilateral arm flexion as quickly as possible and then stopped their arms voluntarily at a horizontal position. After 5 practice trials, test trial was performed 10 times with a 30 s-rest between the trials. Electromyograms (EMG) were recorded from the tibialis anterior (TA), gastrocnemius (GcM), rectus femoris (RF), biceps femoris (BF), and anterior deltoid (AD). The relative number (%) of subjects who showed the EMG burst of postural muscle was 80% in TA, 100% in GcM, 68% in RF, and 100% in BF. The relative frequency (%) of the trials in which the EMG burst was observed was higher in the following order; 57% in GcM only, 26% in TA-GcM, and 5% in TA only for the lower leg, and 65% in BF only, 30% in RF-BF, and 2% in the RF only for the thigh. Start time (mean ± standard deviation) of each muscle with respect to onset of AD was earlier in the following order; TA (-16 ± 39 ms), BF (20 ± 19 ms), GcM (43 ± 29 ms) and RF (47 ± 51 ms). In the children, unlike adults, TA was also activated in many subjects and the preceding activation to AD was not observed in BF. In addition, large inter- and intra-individual differences were indicated.