title: Memory performance during G exposure as assessed by a word recognition task.
abstract: 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.
  
  
  METHODS
  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 1 G. In addition, each subject performed the CRT in a 1-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 1 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.
  
  
  CONCLUSIONS
  The results indicate that memory encoding, but not retrieval, was affected negatively when exposed to substantial and sustained +Gz loads.
authors.affiliation: Swedish Defence Research Agency, Command and Control Systems, Man-System-Interaction, S-581 11 Linköping, Sweden. britta.levin@foi.se
authors.forename: Britta
authors.initials: B
authors.lastname: Levin
authors.forename: Jan
authors.initials: J
authors.lastname: Andersson
authors.forename: Thomas
authors.initials: T
authors.lastname: Karlsson
mesh_terms: D000337:Aerospace Medicine; D001794:Blood Pressure; D003071:Cognition / Q000502:physiology*; D004562:Electrocardiography; D006801:Humans; D018471:Hypergravity / Q000009:adverse effects*; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D021641:Recognition, Psychology / Q000502:physiology*; D012660:Semantics