We investigated the change in the beta band activity on an electroencephalogram (EEG), which reflects the cortical activity, during a long-term visual search.
Eleven subjects performed a long-term visual search task. This task was an Advanced Trail Making Test random task conducted using a computer mouse connected to a personal computer. When the task was started, thirty numbered black circles were displayed randomly; the subjects clicked these circles in numerical order (11–40) with their right hand. On clicking, a circle disappeared, and immediately a circle with a number ＋30 appeared on the screen. The subjects were instructed to click the circles as quickly as possible, and the task was finished when circle No. 40 was clicked. Each subject performed 20 trials of this task. EEG data was obtained using 19 electrodes–connected according to the international 10–20 system. The EEG data was bandpass filtered between 3 and 30 Hz and fast Fourier transformed. Next, the power of the beta band (13–30 Hz) was calculated. We compared the performance time and beta power for each electrode during the first 10 and latter 10 trials.
In the result, the performance and beta power for the frontal, parietal, somatosensory and motor cortices were significantly more during the latter 10 trials than the first 10 trials.
These findings suggest that long-term visual search decreases selective and sustained attention, and then increases task-irrelevant activity in the superior frontal, middle frontal and superior parietal cortices.
We investigated the effects of voluntary neck flexion (NF) and vibrational stimulation (VS) to the neck extensor muscles on saccadic reaction time (SRT) and the changes in cerebral oxygenated hemoglobin concentration (oxy-Hb). Oxy-Hb was measured from frontal area to observe attentional modulation, sensory-motor area for sensory-motor activity of neck extensor muscles, and occipital area for visual processing. Subjects were 13 young healthy adults, who performed reflexive-visually guided saccades for 2 min in three conditions; sitting in rest neck (RN) position, NF position, and VS to the neck extensor muscles. SRT was shorter in NF and VS than RN. In NF, SRT was the shortest for the first 10 s, and oxy-Hb showed the greatest initial increase in all areas, especially in occipital area by that time. After the initial increase, oxy-Hb decreased and from 1 min again started to gradually increase in all areas. Under VS, oxy-Hb showed a significant decrease in all areas, especially for the first 30 s, without initial increase. By the second minute oxy-Hb returned towards the base-line, with similar changing pattern as in NF, especially in the frontal area. These results could suggest that SRT shortening by NF and VS are regulated by different mechanisms.
We investigated weighting to visual information provided at the various floor oscillation timings while standing. Subjects were 13 healthy young adults. First, subjects adapted to the floor oscillation with eyes closed in 0.5 Hz frequency and 2.5 cm amplitude. Next, floor oscillation was applied to the subjects for 2 minutes with visual stimulation at the following oscillation points: (1) anterior and (2) posterior reversal points, the midpoints of (3) forward translation and (4) backward translation. In each condition, visual stimulation with white and black vertical stripes was presented for 40 ms by opening a shutter-goggle. Mean speed of the center of foot pressure was significantly smaller in (2), (3) and (4) than in eyes closed condition. Negative peak of event-related potential was observed near the anterior reversal point in all conditions. Positive peak (P200) amplitude of visual evoked potential observed 200 ms after visual stimulation onset was significantly larger in (4) than (1) and (2). A significant negative correlation was recognized between P200 amplitude and SD of head sway (r = 0.58). It is considered that in all visual stimulation conditions, attention was directed to somatosensory stimulation arisen in a close timing with the anterior reversal point, as well as in the condition with eyes closed. The weighting to visual information was the largest in (4), and it would be closely correlated with phase delay of the head movement against the floor movement. Weighting to the sensory information during floor oscillation would be dynamically modulated according to the utility.
The present study investigated cortical oxygenation in the sensorimotor cortex (SMC) and the concomitant cardiovascular responses during preparation period either followed by maximal voluntary handgrip exercise (Ex) or no exercise (Con) in 13 healthy subjects. We measured levels of oxygenated hemoglobin (oxyHb), deoxygenated hemoglobin (deoxyHb) and total hemoglobin (totalHb) in the SMC by near-infrared spectroscopy and simultaneously recorded heart rate (HR). During 30 seconds before the exercise in Ex, the oxyHb and totalHb in the Premotor cortex (PMC) were significantly higher than those in Con, and deoxyHb was lower than that in Con. These changes in Ex indicated a significant increase in regional cerebral blood flow resulting from neuronal activation in the PMC. In accord with the cerebral changes, HR was elevated significantly in Ex but not in Con. These results suggested that the increases in HR in Ex were coupled with the cortical activation in the PMC resulting from high intensity exercise preparation.
We examined whether inhalation of hyperoxic gas improved arterial hypoxemia caused by sprint exercise (EIAH) reported in women. Twelve female university students performed 30 seconds of all-out exercise on a cycle ergometer under two conditions: inhalation of normoxic gas (FIO2 = 0.21) or hyperoxic gas (FIO2 = 0.27). Arterial oxygen saturation of hemoglobin via pulse oximetry (SpO2), heart rate (HR) and blood pressure (BP) were assessed at rest, immediately after and during recovery from the exercise. Ratings perceived exertion (RPE) were obtained immediately and 5 minutes after the exercise. Six of the 12 women experienced EIAH under normoxic condition. In these 6 women, SpO2 declined to 88.7 ± 2.5% within 10 to 14 seconds after completion of the exercise under normoxic condition but remained at 94.7 ± 1.4% under hyperoxic condition. Of the 6 women placed under hyperoxic condition, 3 women did not exhibit EIAH. In contrast, HR, BP and RPE responses to the exercise were comparable under both conditions. Thus, these findings suggest that arterial hypoxemia resulting from sprint exercise might be alleviated with 27% hyperoxic gas inhalation in women.