The present study investigated changes in circulatory dynamics of upper extremity muscles during a task involving maintaining neck flexion and during the neck flexion task accompanied with an eye movement reaction task. Neck flexion angles were randomly set at 0°, 10° and 20°. Muscle oxygenation in the biceps brachii and triceps brachii, skin blood flow over the muscles, electrocardiograms, blood pressure and cardiac output were measured during both tasks. During the neck flexion task, oxygenation in muscles increased significantly with angle of neck flexion. Oxygenation in muscles tended to be larger in the neck flexion task with the eye movement reaction task than in the neck flexion task alone. A significant difference between tasks was found at 20° flexion. Furthermore, skin blood flow over the biceps brachii tended to be smaller under the combined task than under the neck flexion task alone. A significant difference between tasks was found at 20° flexion. No significant task effects were found in electrocardiograms, blood pressure or cardiac output. Blood flow within upper extremity muscles was clearly increased while maintaining neck flexion. Blood flow increased more when the neck-flexion task accompanied the eye movement reaction task. This suggests that brain activation associated with maintaining neck flexion influences the vasomotor center in the medulla oblongata controlling circulatory responses, leading to vasodilatation in muscles. Furthermore, additional brain activation appears to offer synergistic effects during the combined neck flexion and eye movement reaction tasks, and reduction of skin blood flow by skin vasoconstriction might be related to increased blood flow in addition to vasodilatation in muscles.
We examined the information processing in the cerebral cortex of the human during the anticipation-response timing task by electroencephalogram (EEG). In addition, we investigated the area related to the accurate timing function in the cerebral cortex of the human.
We used two tasks, the control task and the anticipation-response timing tasks, to examine the information processing in the brain in the timing task. Both task were carried out using a computer display placed approximately 1.5 m away from the subject.
An EEG was recorded from electrodes placed at 128 sites on the scalp. The EEG was separated into frequency bands of beta waves (13-30 Hz) and analyzed.
The beta wave in the task execution was synthesized with 3 dimension models that were made from the MRI image and was analyzed at 2ms intervals.
The results were as follows. 1) After excitation in the visual area: the excitation from the occipital association area was moved to parietal association area and temporal association areas, then from these two association area to the prefrontal area and the motor association area. 2) After excitation motor association area: the prefrontal area and the parietal association area repeated the excitation around the motor association area. This activity was observed only in the timing task. 3) In the timing task in comparison with the control task, activation of the motor association area, the parietal association area, the temporal association area and the visual area was observed. 4) It was suggested that the left motor association area, the right parietal association area and the right temporal association area are became involved especially in the accurate timing response.
This study was done to examine which of the frequency components of the EEG beta wave, shows chronological changes in cerebral information processing during a simple reaction task by image visual stimulus. Then the fast reaction and the slow reaction were compared and examined.
Seven healthy subjects（all right-handed）were studied. As the image stimulus, the subject was presented with images for 300 ms from a computer display. Each subject was instructed to push a button with the right thumb when he or she perceived the image stimulus. An EEG was recorded from the scalp by 128 channels, and it was separated into frequency bands of beta waves（13 to 30 Hz）and then analyzed. The brain potential distribution was image processed chronologically on a three-dimensional MRI image every 2 ms, and presented as excitation areas in the brain and was analyzed.
The chronological changes in the beta wave band in the left brain and the right brain were as follows: After excitation from the visual stimulus reached the visual cortex, the excitation was transmitted to the parietal association area and the temporal association area, and then from these two association areas to the frontal association area. This pathway was shown two times at onset. When the reaction time was delayed, the frequency of excitation in the frontal association area, the temporal association area and the visual cortex increased.
The results indicate that the frontal association area and the temporal association area probably play an important role in decision-making for a fast reaction.
The posterior auricular muscle response（PAMR）and middle-latency auditory response（MLR）evoked by auditory stimuli were examined to know the changes in activation degree of auditory neural circuit while maintaining neck flexion. Fourteen healthy subjects heard click sounds via headphones. The click frequency was 8 Hz and the intensity was 50 dB above hearing threshold. Measurement was carried out with the neck flexed at 0°, 10°and 20°. The PAMR and MLR were simultaneously measured in the neck flexion condition. One trial was 30 seconds, it repeated 5 times with a 30 seconds rest and total of click stimulations in each session was 1000. In the PAMR, the amplitude increased according to the neck flexion, and the latency shortened. In the MLR, the components（Po, Na）with latencies that were almost corresponding to the PAMR（p1, n2）existed. However, the changes in the both responses according to the neck flexion were not so similar as to be able to say that they were influenced by quite the same factor. The change in the latter component of the MLR according to the neck flexion showed the lower similarity to the PAMR.