Memory performance during G exposure as assessed by a word recognition task

Background: Pilots of modern fighter aircraft are exposed to substantial physiological and mental stressors. The objective of this study was to investigate how memory performance, in terms of encoding and/or retrieval processes, was affected by sustained +Gz exposure. Method There were 18 healthy men ranging from experienced fighter pilots to novice riders who participated. A word continuous recognition task (CRT) was employed as a memory test. The task consisted of three consecutive phases: 1) encoding of familiar words at 1 G; 2) encoding and retrieval of words at 70% of the subject's relaxed G-tolerance level, equivalent to +3.7 +/- 0.54 Gz; and 3) encoding and retrieval of words at I G. In addition, each subject performed the CRT in a I-G-only control condition. Physiological and psycho-physiological measures included continuous monitoring of ECG, arterial oxygen saturation, arterial BP at head level, and response time. Results: Data analysis showed that the capability to recognize words encoded at I G did not differ between conditions, indicating that the retrieval process was insensitive to increased Gz load. However, the ability to recognize words previously encoded during G exposure was reduced by approximately 10% as compared with control. Since the analysis revealed that the words were perceived, this result suggests that the encoding process was impaired in hypergravity. Conclusion: The results indicate that memory encoding, but not retrieval, was affected negatively when exposed to substantial and sustained +Gz loads.