Variation in mental performance under different levels of heat stress-induced dehydration was recorded in 11 subjects heat acclimatized to the tropicals. Dehydration was induced by a combination of water restriction and exercise in heat. The psychological functions--arithmetic ability, short-term memory, and visuomotor tracking--were assessed in a thermoneutral room after the subjects recovered fully from the effects of exercise in heat, as reflected by their oral temperature and heart rate. The results indicated significant deterioration in mental functions at 2% or more body dehydration levels.

Studies were carried out to find out the role of chemoreceptor sensitivity in the causation of maladaptation syndromes on acute exposure to altitude. The experiments were done in two phases. In phase I, the responses in chemoreceptor sensitivity were studied in altitude acclimatized subjects and compared with those who suffered from either High Altitude Pulmonary Oedema (HAPO) or Acute Mountain Sickness (AMS). In Phase II, a similar comparison was done in two groups of subjects, one representing normal sojourners at 3,500 m and the other being subjects who had just recovered from HAPO. The first phase was done at Delhi; and the second at an altitude of 3,500 m. Parameters of assessment were hypoxic sensitivity, carbon dioxide sensitivity, ventilation (VE), respiratory frequency (Rf), forced vital capacity (FVC), forced expiratory volume at the first second (FEV1), heart rate (HR), blood pressure (BP), and oral temperature (Tor). The results showed significantly lower sensitivity to both hypoxia and carbon dioxide in maladapted subjects, as compared to those who were acclimatized in both the categories suggesting thereby that reduced chemoreceptor sensitivity might be an initiating factor in the causation of maladaptation syndromes at altitude.

The efficacy of a composite Indian herbal preparation (CIHP) in sustaining the mental performance of soldiers engaged in prolonged low-intensity-conflict operations has been evaluated. For this purpose, a cohort of 56 soldiers acted as volunteers in combat situations. After recording their initial responses to psychological tests such as the d2 test, the trail-making test, the serial addition test, the short-term memory test, and the Institute for Personality and Ability Testing Anxiety Scale, they were randomly given either CIHP or placebo in a double-blind fashion for 8 days while they performed their usual combat duties. The final 3 days of assignments included physically exhausting and life-threatening events. On day 8, they were withdrawn from combat duties and the psychological tests were readministered immediately. After 7 days of rest, the tests were repeated once again. The results indicate comparatively better performance immediately after the mission by the CIHP group. CIHP was effective at sustaining the mental abilities of soldiers in a low-intensity-conflict environment.