Biomedical subjects

Arihiro Hatta

Publications and source records attributed to Arihiro Hatta.

8 recordsLinked to original sources

PubMed2005

Effects of habitual moderate exercise on response processing and cognitive processing in older adults.

We examined the effects of habitual moderate exercise on central information processing in older individuals using the reaction time (RT) and P3 component of event-related brain potentials (ERP). The present study was designed to assess cognitive function by comparing groups of 20 older individuals (69.20 +/- 1.3 years active group) who regularly engage in moderate physical activity with 20 subjects (66.90 +/- 1.1 years inactive group) who do comparatively little exercise. Subjects performed a somatosensory oddball task composed of pressing a button with their right foot as fast as possible following an electrical stimulus applied to the right index finger, and not responding to an electrical stimulus applied to the left index finger. Electroencephalogram (EEG) was recorded at the frontal (Fz), central (Cz), and parietal (Pz) sites according to the International 10-20 system referenced to linked earlobes. The RT was faster for the active group than for the inactive group, and the P3 amplitude of the active group was significantly larger than that of the inactive group. Moreover, the P3 amplitude for the active group was maximum at Pz and significantly larger than at Fz and Cz, but for the inactive group it was identical between Fz and Pz. The results suggest that habitual moderate exercise exerts positive influences in older adults not only on response processing, but also on cognitive processing.

Aged↗

PubMed2004

Differential influences of exercise intensity on information processing in the central nervous system.

The influence of exercise intensity on information processing in the central nervous system was investigated using P300 and no-go P300 event-related potentials. Twelve subjects (22-33 years) performed a go/no-go reaction time task in a control condition, and again after high-, medium-, and low-intensity pedaling exercises. Compared to the control condition, P300 amplitude decreased after high-intensity pedaling exercise and increased after medium-intensity pedaling exercise. There was no change after low-intensity pedaling exercise. These results suggested that the amount of attentional resources devoted to a given task decreased after high-intensity exercise and increased after medium-intensity exercise. The findings also suggest that changes in P300 amplitude are an inverted U-shaped behavior of differences in exercise intensity. In addition, no-go P300 amplitude showed the same changes as P300 amplitude at different exercise intensities. This indicates that differences in exercise intensity influenced not only the intensity of processing the requirement for a go response, but also processing of the need for a no-go response. It is concluded that differences in exercise intensity influenced information processing in the CNS.

Adult↗

PubMed2004

Effects of a go/nogo task on event-related potentials following somatosensory stimulation.

OBJECTIVE: We investigated the effects of a go/nogo task on event-related potentials (ERPs) evoked by somatosensory stimuli. METHODS: ERPs following electrical stimulation of the second (go stimulus) or fifth (nogo stimulus) left-handed digit were recorded from 9 subjects. The recordings were conducted in 3 conditions: Control, Count and Movement. The subjects were instructed to count the go stimuli silently in Count, and respond to the go stimuli by grasping right hands in Movement. Go and nogo stimuli were presented at an even probability. RESULTS: N140 was recorded in all conditions and P300 in Count and Movement. The mean amplitudes of the nogo stimuli in the interval 140-200 msec and nogo-N140 amplitude were significantly more negative than those of the go stimuli in Count or Movement. Nogo-P300 was larger in amplitude than go-P300 in Movement but not Count. The effect of P300 was applied to Fz and Cz, but not at Pz. CONCLUSIONS: In the present study, effects of a somatosensory go/nogo task on ERPs were investigated, and our findings were very similar to those of previous studies using visual and auditory go/nogo tasks. Therefore, we suggest that cortical activities relating to go/nogo tasks are not dependent on sensory modalities. SIGNIFICANCE: The present study showed for the first time the go/nogo effects on somatosensory-evoked ERPs. These effects were similar to those in visual and auditory ERP studies.

Acoustic Stimulation↗

PubMed2004

Resource allocation and somatosensory P300 amplitude during dual task: effects of tracking speed and predictability of tracking direction.

OBJECTIVE: The amount of attentional resources allocated to a task is determined by the intrinsic demands, also denoted as task load or difficulty of the task. Effects of resource allocation on the somatosensory N140 and P300 were investigated in an inter-modal situation using a dual-task methodology. METHODS: Under a dual-task condition, subjects concurrently performed a visuomotor tracking task and a somatosensory oddball task, while they performed just the oddball task under an oddball-only condition. In the tracking task, the subjects tracked the target line, which was presented on an oscilloscope and automatically moved, with the line which represented their own force generated by grip movement with the left hand. Tracking speed (experiment 1) and tracking predictability (experiment 2) were manipulated to vary task difficulty. N140, P300, and reaction time (RT) in the oddball task and tracking accuracy in the tracking task were measured. RESULTS: The P300 and N140 amplitudes were reduced in the dual-task condition compared to those in the oddball-only condition. The fastest tracking speed produced lower tracking accuracy and later RT. However, the tracking speed did not affect the P300 or N140 amplitudes. In contrast, the P300 amplitude was smaller when the change in tracking direction was unpredictable than when it was predictable, without any differences in tracking accuracy or RT, N140. CONCLUSIONS: The differences in behaviors among N140, P300, and RT following manipulation of task difficulty support the multiple-resource hypothesis, which defines functionally separate pools of resources. SIGNIFICANCE: The present study may show that the P300 amplitude reflects modality-unspecific resource at more central level, and that the N140 amplitude involves perceptual resource.

Adult↗

PubMed2004

Changes in arousal level by differential exercise intensity.

OBJECTIVE: The purpose of the present study was to investigate the influence of exercise intensity on arousal level. METHODS: Twelve subjects (22-33 years) performed a S1-S2 reaction time task consisting of warning stimulus (S1) and imperative stimulus (S2) in a control condition, and again after low, medium, and high intensity pedaling exercises. During this task, contingent negative variation (CNV) and spontaneous electroencephalogram before S1 were measured as indicators for arousal level. RESULTS: CNV amplitude after high intensity pedaling exercise was significantly smaller than after medium pedaling exercise. Compared to the control condition, relative power value of alpha waves increased after the high intensity exercise. CONCLUSIONS: These results suggested that arousal level was reduced after high intensity exercise and reached a state near optimal level after medium intensity exercise. The findings also suggested that changes in CNV amplitude by differences in exercise intensity followed an inverted-U shaped dose response curve. SIGNIFICANCE: The present study supported the view that CNV amplitude and arousal level followed an inverted-U relationship. It is concluded that differences in exercise intensity influenced arousal level.

Adult↗

PubMed2003

Changes in the somatosensory N250 and P300 by the variation of reaction time.

We investigated the relationship between somatosensory event-related potentials (ERP) and the variation of reaction time (RT). For this purpose, we recorded the ERPs (N250 and P300) in fast- and slow-reaction trials during a somatosensory discrimination task. Strong, standard, and weak target electrical stimuli were randomly delivered to the left median nerve at the wrist with a random interstimulus interval (900-1,100 ms). All the subjects were instructed to respond by pressing a button with their right thumb as fast as possible whenever a target stimulus was presented. We divided all the trials into fast- and slow-RT trials and averaged the data. N250 latency tended to be delayed when the RT was slow, but not significantly. P300 latency was delayed significantly when the RT was slow, but to a much lesser extent than the RT delay, so we concluded that the change of RT was not fully determined by the processes reflected by the somatosensory N250 or P300. Furthermore, the larger and earlier P300 in the fast-RT trials implied that when larger amounts of attentional resources were allocated to a given task, the speed of stimulus evaluation somewhat increased and RT was shortened to a great extent. N250 amplitude did not significantly vary in the two RT clusters. In conclusion, the somatosensory N250 reflects active target detection, which is relatively independent of the modulation of the response speed, whereas the somatosensory P300 could change without manipulation of either the stimulus or the response processing demand.

Adult↗

PubMed2003

Somatosensory N250 and P300 during discrimination tasks.

We investigated the event-related potentials (N250 and P300) during three kinds of somatosensory discrimination tasks (oddball task). Strong (standard: 90%) and weak (deviant: 10%) electrical stimuli were randomly delivered to the right median nerve at the wrist with a 500-ms constant interstimulus interval. In a passive situation, subjects read a self-selected book, ignoring all stimuli (ignore condition). One of the active situations was a mental counting task (count condition), and another required pressing a button to deviant stimuli as quickly as possible (motor response condition). The N250-P300 complex was elicited by deviant stimuli in the active-attended situations, but not found in the ignore condition. The N250 peak amplitude was unchanged between the count and motor response conditions whereas P300 changed. In addition, the N250 latency significantly correlated with the reaction time, but the P300 latency did not. These results indicate that the somatosensory N250 reflects an attentive process which is related to the temporal aspect of behavioral response.

Adult↗

PubMed2003

Somatosensory event-related potentials (ERPs) associated with stopping ongoing movement.

The somatosensory event-related potentials (ERPs) associated with stopping ongoing movement and increasing muscular tension were examined. 14 healthy right-handed volunteers, 10 men and 4 women (21-29 years old, M age +/- SD, 24.1 +/- 2.5 yr.) performed a stop/increase reaction task. They were requested to perform an elbow extension movement with the right arm and to maintain 20% of the maximum voluntary contraction forces (MVC) before the electrical stimuli were delivered to either the left index finger or the left little finger. They executed one of two movements from the sustained contraction state: they had to stop the muscular tension following the left little finger stimulus or increase the muscular tension from 20% to 40% of the maximum voluntary contraction forces following the left index finger stimulus. The reaction time and somatosensory sequence P100-N140-P300 components of event-related potentials were recorded for each electrical stimulus, respectively. The reaction time was longer to the increase reaction condition than to the stop reaction condition. Neither P100 nor N140 components showed significant differences between stop and increase reaction conditions. The P300 to the stop reaction condition was of greater amplitude and latency than those of the increase reaction condition. These results suggest that stopping the ongoing movement processing requires a longer stimulus evaluation time and is more demanding than increasing reaction processing.

Adult↗