Neuroendocrine responses to psychological workload of military flying

Abstract

The psychological workload a pilot is exposed to during military flying is considered to be high, and good stress tolerance is needed. During military flying a huge amount of environmental information is transformed to neural signals which finally lead to motor and behavioral changes, and also to chemial secretion of neuroendocrine hormones.

This study deals with neuroendocrine measurements performed in four procedures: psychomotor test during military pilot selection, instrument flying (IFR) with piston-engine primary trainer, real and simulated jet trainer flight, and simulated combat fighter flight. Neuroendocrine hormones, hypothalamic CRH, pituitary ACTH, beta-endorphin, prolactin and vasopressin, the adrenal hormones cortisol, adrenaline and noradrenaline and a cardiac hormone, ANP, were assayed from plasma by using immunoassay and HPLC techniques.

In the psychomotor test (procedure 1) plasma prolactin, ACTH and cortisol responses were associated with a high number of delayed responses, which was used as an indicator of information overload. Anticipatory type ACTH response, i.e. high ACTH level before the test, predicted poor overall result in the psychomotor test. In response to IFR flying (procedure II) the student pilots showed increased plasma prolactin, ACTH, cortisol, adrenaline and noradrenaline levels. Postflight adrenaline response correlated significantly with poor flight performance as well as a poor psychomotor test result. Low emotional control and high performance motivation measured by an aviation psychologist correlated significantly with neuroendocrine responses after the instrument flight. Flight with jet trainer (procedure III) led to increased plasma prolactin levels, evidently due to psychological workload, but no statistically significant plasma prolactin increase was found in the simulator. This suggests that psychological workload in the flight simulator is lower compared to real jet trainer. A significant ANP response to jet trainer flight was apparently associated with increased heart rate due to psychological workload of the flight mission. Simulated combat fighter flight (procedure IV) resulted in an anticipatory type stress reaction as judged from the elevated preflight plasma ACTH, and a direct type reaction was observed in cortisol. In one pilot the neuroendocrine activation was extreme and global, suggesting low stress tolerance under high information load.

Increased neuroendocrine activation is associated with psychological workload of military flying. Neuroendocrine measurements can be used in a follow-up system of military pilots.