Meditation as an intervention for cognitive disturbances following total sleep deprivation.

Background & objectives: Decline in cognitive functions is a major challenge for professionals during sustained wakefulness. We used middle latency response (MLR), event related potentials P300-ERP and contingent negative variation (CNV) and Raven’s Advanced Progressive Matrices (RAPM) - a standard neuropsychological test were used to evaluate cognitive impairment after total sleep deprivation (SD); and to study the impact of meditation as an intervention for this impairment. Methods: Healthy male volunteers (n=10) drawn randomly from the Indian Army participated in a 6-night study design executed before and after two months of meditation practice: night 1–adaptation, night 2–baseline, night 3–24 h SD, night 4–recovery sleep, night 5–24 h SD after 60 days meditation, night 6–recovery sleep after SD. A 36 h SD was obtained by keeping the subject awake for 12 h after 24 h SD. Results: The latency and amplitude of P300 increased after 36 h SD. Amplitudes and latencies of both early and late CNV increased after 24 and 36 h SD, indicating deficient orientation and impairment of attention and perception. Prolonged CNV reaction time after 36 h SD manifested deficient motor response following second (imperative) stimulus. Latency of MLR Na registered significant change following 36 h SD compared to baseline (P<0.01) and recovery (P<0.05). RAPM score showed significant decrease after 36 h of wakefulness indicating impaired analytical ability and difficulty in problem solving. None of these parameters showed any significant alteration after SD, following meditation practice. Interpretation & conclusions: The present results showed that SD impaired cognitive performance to graded extents significantly, but this deterioration could be improved to a significant extent using meditation.

Sleep architecture at 4300 m altitude in a sample of Indian lowlanders.

The present study aimed to evaluate sleep architecture at 4300m in a sample of 10 healthy Indian lowlanders, mean age 25.7±5.1 yrs. Polysomnography on two consecutive nights each was performed at sea level and 4300 m, the first night for adaptation and the second one for actual recording. Total sleep time reduced from 433.33±8.95 to 412.06±13.13 minutes (P<0.0005), sleep latency increased from 11.56±6.85 to 22.22±7.95 minutes (P<0.0025), deep NREM sleep (S3+S4) reduced from 79.56±28.45 to 45.39±25.32 minutes (P<0.01), light NREM sleep (S1+S2) increased from 272.94±20.63 to 296.72±23.24 minutes (P<0.05), REM decreased from 80.89±7.65 to 69.94±11.30 minutes (P<0.02) and periodic breathing was present in 4 of 10 participants on the second night at 4300 m. Decreased sleep quality (P<0.0005) and increased sleep disturbances (P<0.0005) were reported in subjective ratings at high altitude. Changes in sleep architecture similar to but of a greater magnitude are present on the second night of staged induction to 4300 m, than reported at 3500 m in our earlier study.

Event related potential (ERP) P300 after 6 months residence at 4115 meter.

Background & objectives: The P300 wave is an event related potential (ERP) elicited by infrequent, task-relevant stimuli and appeared at about 300 ms, represents higher cognitive function of information processing, working memory or stimulus categorization. Hypobaric hypoxia deteriorates the cognitive function during the short term stay (days to few weeks) at high altitude. The present study was carried out to evaluate the P300 responses during long duration stay (1 month and 6 months) at high altitude (HA, 4115 m) in a sample of Indian lowlanders. Methods: The study was carried out on 18 healthy male volunteers at sea level (SL). The volunteers were stage inducted to 4115 m altitude in the Eastern Himalayas. The P300 was recorded after 1 and 6 months of their stay at HA. Results: The latencies of peaks N100, P200 and N200 waves did not show any significant changes after 1 and 6 months of stay at HA as compared to SL. The P300 latency was significantly delayed after 1 month and further delayed after 6 month of residence at 4115 m. The P200 and P300 amplitudes did not show any changes. Interpretation & conclusions: The increase in P300 latency indicated that long duration of stay at high altitude slows the stimulus evaluation processes. The observations suggest that hypoxia causes slowing of the signal processing at HA. The magnitude of the effects of hypobaric hypoxia may be dependent upon the duration of residence at high altitude.

Effect of simulated ascent to 3500 meter on neuro-endocrine functions.

Ascent to extreme High Altitude (HA) is in steps and it entails acclimatization at moderately HA locations. In terms of acclimatization, it is pertinent to understand the physiological changes, which occur on immediate ascent to moderate HA. The study aimed to evaluate the effect of ascent to 3500 m on neuro-endocrine responses in the first hour of induction. The plasma levels of catecholamines and cortisol were measured before and after one hour of ascent to high altitude. The peripheral oxygen saturation (SpO2), Galvanic Skin Resistance (GSR), Heart Rate (HR) and Blood Pressure (BP) were simultaneously monitored. The plasma epinephrine, norepinephrine, dopamine and cortisol were increased after one-hour exposure to 3500 m altitude as compared to before exposure. The SpO2 showed a significant decrease during and after high altitude induction. The heart rate and diastolic BP increased at 3500 m whereas the GSR did not show significant changes. There are changes in neuroendocrine responses, which reflect a sympathetic over activity in the first hour of exposure to 3500 m.