title: Nitrogen narcosis and tactile shape memory in low visibility.
abstract: OBJECTIVE
  Commercial diving often occurs in low visibility, where divers are reliant on their tactile senses. This study examined the effect of nitrogen narcosis on tactile memory for shapes as well as the influence of psychological and biographical factors on this relationship.
  
  
  METHODS
  This crossover study tested 139 commercial divers in a dry hyperbaric chamber at 101.325 and 607.95 kPa (1 and 6 atmospheres absolute/atm abs). Divers memorized shapes while blindfolded, using their tactile senses only. Delayed recall was measured at the surface after each dive. Psychological and biographical data were also collected.
  
  
  RESULTS
  A significant effect of hyperbaric pressure on tactile memory was demonstrated, and a further effect of sequence of testing found. Thus, divers' delayed shape recall deteriorated by 8% after learning material at depth, compared to learning on the surface. There were also significant but small effects of psychological and biographical markers on tactile memory performance, with lower trait anxiety associated with better recall, and lower education associated with poorer recall.
  
  
  CONCLUSIONS
  The findings emphasize the importance of utilizing other forms of recording of events or objects at depth, particularly in conditions of low visibility during deeper diving, to aid memory encoding and subsequent recall at the surface.
authors.affiliation: Stellenbosch University, South Africa. chvanwijk@gmail.com
authors.forename: Charles H
authors.initials: CH
authors.lastname: van Wijk
authors.forename: W A J
authors.initials: WA
authors.lastname: Meintjes
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001007:Anxiety / Q000175:diagnosis / Q000523:psychology; D004242:Diving / Q000009:adverse effects / Q000502:physiology; D004522:Educational Status; D005260:Female; D006801:Humans; D007222:Inert Gas Narcosis / Q000150:complications / Q000503:physiopathology* / Q000523:psychology; D008297:Male; D011939:Mental Recall / Q000502:physiology*; D009483:Neuropsychological Tests; D010555:Personality Inventory; D013236:Stereognosis / Q000502:physiology; D014110:Touch / Q000502:physiology*; D055698:Touch Perception / Q000502:physiology*; D055815:Young Adult