Biomedical subjects

Sabyasachi Sircar

Publications and source records attributed to Sabyasachi Sircar.

3 recordsLinked to original sources

PubMed2005

Post-task changes in visual P300 and their reversibility through brief hyperventilation.

Long hours of continuous, mental task reportedly increase the average auditory P3 latency of the normal subjects significantly, a change that is thought to be related to mental fatigue. We have tried out several protocols of varying task difficulty and duration in an effort to study the onset of the assumed fatigue-related changes. The present study shows that changes in visual event-related potential occur in less than two minutes if the task is sufficiently rigorous. The changes occur both in latency and in amplitude. Moreover, the changes are reversible with a brief (30 second) period of hyperventilation. The changes were most marked at Fz. Following the difficult task, the P3 amplitude at Fz decreased from 8.588 micro/V +/- 0.966 to 5.800 microV +/- 0.795 and the P3 latency increased from 368 +/- 4 ms to 380 +/- 3. Following hyperventilation, the P3 amplitude at Fz reverted to 8.457 +/- 5 and the P3 latency reverted to 371 +/- 5 ms. These observations call for further investigations on the cause of the post-task changes and their quick reversibility.

Adult↗

PubMed2004

Role of uterine artery velocimetry using color-flow Doppler and electromyography of uterus in prediction of preterm labor.

AIM: To evaluate the role of Doppler waveforms of uterine vessels and electromyography (EMG) of the uterus in predicting preterm labor. METHODS: One hundred ante-natal women at >or=24 weeks of gestation who fulfilled the selection criteria were included in the study. A single Doppler recording for bilateral uterine vessels was taken at >or=26 weeks gestation using the transvaginal route. Transabdominal EMG of the uterus was recorded serially at 4-week intervals from 24 weeks until delivery or until 37 weeks were completed. RESULTS: Women with a sensation of heaviness in the lower abdomen during pregnancy had a significant association with preterm delivery. Of the three Doppler indices, the systolic/diastolic ratio and the resistivity index of uterine vessels were found to have a sensitivity as high as 83-95% for the prediction of preterm labor. The electrical activity of uterine musculature, as recorded using EMG, showed that there was a statistically significant difference between the electrical activity recorded for the two groups at 31 weeks and later, while the duration of burst activity was significantly longer in the preterm group at 26 weeks and later. CONCLUSIONS: Patients with a dull aching sensation in the lower abdomen should not be neglected. Doppler of the uterine vessels and EMG of the uterus could prove to be a good predictor of preterm labor.

Adolescent↗

PubMed2004

Post-task P3-changes following a brief, rigorous visual task indicate individual differences in the task-specific ability.

The P3 latency in an auditory oddball ERP paradigm is known to get prolonged after a few hours of mental task. The present study shows that it takes merely a few minutes of challenging visual mental activity to produce significant changes in P3 latency in the visual oddball ERP paradigm. However, the mental activity results in a shortening of P3-latency almost as often as it results in its prolongation. Similarly, the post-task P3 amplitude is higher or lower with nearly equal incidences. Following the task, the reaction time shortens as often as it prolongs. It seems that the P3 changes and their variations through electrode sites signify individual differences in the amount and extent of additional neuronal resources tapped by the subject in coping with the challenging task, and that it leaves an aftereffect for several minutes after the mental workload is withdrawn. These aftereffects get indexed in the P3 wave characteristics of a much simpler ERP paradigm with more change occurring in the better performers. In the clinical context, these observations raise doubts about the diagnostic value of P3 latency or amplitude without knowledge of the immediate history of mental workload.

Adolescent↗