Biomedical subjects

Tetsuo Kida

Publications and source records attributed to Tetsuo Kida.

27 records · Page 2Linked to original sources

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↗

PubMed2004

Differential modulation of temporal and frontal components of the somatosensory N140 and the effect of interstimulus interval in a selective attention task.

The modulation of the somatosensory N140 was examined in a selective attention task where a control condition was applied and the interstimulus interval (ISI) was varied. Electrical stimuli were randomly presented to the left index (p=0.4) and middle fingers (p=0.1), and right index (p=0.4) and middle fingers (p=0.1). In the attend-right condition, subjects were instructed to count silently the number of infrequent target stimuli presented to the right middle finger, and to the left middle finger in the attend-left condition. They had no task in the control condition. Each condition was performed with two different sets of ISI (mean 400 vs. 800 ms). The somatosensory N140 elicited by frequent standard stimuli was analyzed. The N140 amplitude was larger for the attended ERP compared to the control and unattended ERPs. This attention effect was more marked at the frontal electrodes compared to the temporal electrodes contralateral to the stimulation side. Furthermore, the attention effect at the frontal electrode was larger when the ISI was 800 ms than when it was 400 ms. The N140 amplitude did not differ between the control and unattended ERPs, which might show that a small processing negativity (PN) occurred during the control condition or difference in vigilance level between them. In conclusion, the early lateral ("temporal") and late midline ("frontal") components of the N1 (N140) show different behavior, and thus may have different functional significance. Enhancement of the attention effect at the frontal electrode in the longer ISI condition supports the hypothesis that it is related to stronger, voluntary maintenance of the attentional trace.

Adult↗

PubMed2004

[Investigation of radioactivity measurement of medical radioactive waste].

To explore the possibility of which medical radioactive wastes could be disposed as general wastes after keeping them a certain period of time and confirming that their radioactivity reach a background level (BGL), we made a survey of these wastes in several nuclear medicine facilities. The radioactive wastes were collected for one week, packed in a box according to its half-life, and measured its radioactivity by scintillation survey meter with time. Some wastes could reach a BGL within 10 times of half-life, but 19% of the short half-life group (group 1) including 99mTc and 123I, and 8% of the middle half-life group (group 2) including 67Ga, (111)In, and 201Tl did not reach a BGL within 20 times of half-life. A reason for delaying the time of reaching a BGL might be partially attributed to high initial radiation dose rate or heavy package weight. However, mixing with the nuclides of longer half-life was estimated to be the biggest factor affecting this result. When disposing medical radioactive wastes as general wastes, it is necessary to avoid mixing with radionuclide of longer half-life and confirm that it reaches a BGL by actual measurement.

Half-Life↗

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↗

PubMed2003

[A multicenter evaluation of seven commercial ML-EM algorithms for SPECT image reconstruction using simulation data].

The maximum likelihood expectation maximization (ML-EM) algorithm has become available as an alternative to filtered back projection in SPECT. The actual physical performance may be different depending on the manufacturer and model, because of differences in computational details. The purpose of this study was to investigate the characteristics of seven different types of ML-EM algorithms using simple simulation data. Seven ML-EM algorithm programs were used: Genie (GE), esoft (Siemens), HARP-III (Hitachi), GMS-5500UI (Toshiba), Pegasys (ADAC), ODYSSEY-FX (Marconi), and Windows-PC (original software). Projection data of a 2-pixel-wide line source in the center of the field of view were simulated without attenuation or scatter. Images were reconstructed with ML-EM by changing the number of iterations from 1 to 45 for each algorithm. Image quality was evaluated after a reconstruction using full width at half maximum (FWHM), full width at tenth maximum (FWTM), and the total counts of the reconstructed images. In the maximum number of iterations, the difference in the FWHM value was up to 1.5 pixels, and that of FWTM, no less than 2.0 pixels. The total counts of the reconstructed images in the initial few iterations were larger or smaller than the converged value depending on the initial values. Our results for the simplest simulation data suggest that each ML-EM algorithm itself provides a simulation image. We should keep in mind which algorithm is being used and its computational details, when physical and clinical usefulness are compared.

Algorithms↗

PubMed2003

[Introduction of manual for the management radioactive medical waste].

Societies concerned with radioactive rays and nuclear medicine have recently highlighted the necessity of managing radioactive medical waste resulting from nuclear medicine examinations. We introduce a manual that we have created and explain its use in decision-making and management practices aimed at the reduction of radioactive medical waste at hospitals that have not yet solved this problem. We hope that our manual will help in reducing this medical waste.

Japan↗