A cross-over study investigating specific aspects of neuropsychological performance in hyperbaric environments

[摘要] ENGLISH ABSTRACT: The commercial and military deep diving environment is typically a low visibility environment, where dependence on the visual senses often needs to be replaced by a reliance on tactile senses.This thesis reviewed the current knowledge regarding neuropsychological manifestations of nitrogen narcosis and exposed a number of shortcomings in the current body of knowledge. In particular, the human performance effects of hyperbaric exposure on tactile perception and memory have not been systematically studied. It is further not clear, how exactly psychological factors (e.g. anxiety, mood states) and biographical factors (e.g. age, education, technical exposure, experience) might influence tactile perception and memory performance under conditions of hyperbaric exposure. The correlation between subjective experiences of narcosis, tactile performance, and psychological and biographical variables is also unknown. This study thus set out to investigate certain neuropsychological aspects of nitrogen narcosis, with special reference to tactile perception and memory, and to examine the relationships of tactile performance with other psychological and biographical factors.The effects of experimental hyperbaric exposure (EHE) on tactile (form) perception and tactile shape memory were examined by testing these functions at 6 ATA and 1 ATA, using a cross-over design where two groups completed the same tasks, in opposite sequence. The psychological variables included trait anxiety, transient mood states, and subjective ratings of narcosis, while the biographical variables included age, education, and previous technical exposure.The results demonstrated the detrimental effect of nitrogen narcosis on tactile form perception and manipulation, irrespective of the sequence of testing. It also demonstrated this effect on tactile form memory, although the sequence of testing also played a role here.Higher trait anxiety was associated with poorer recall, and tension was associated with a larger decrement in recall performance, while fatigue was associated with poorer task completion. Subjective experiences also played a role, where feelings of physical anxiety (i.e. increased arousal) were associated with better recall, and feelings of cognitive suppression (decreased arousal) were associated with a larger decrement in recall performance. Lower academic attainment was associated with poorer recall, while higher diving qualification was associated with better recall. Performance on the surface was a good predictor of performance at depth. Qualitative analysis rendered three themes, namely focus vs. distraction, following instructions, and shape memory. Psychometric properties of the subjective narcosis measure were also reported.Theoretical implications include support for the slowed information processing model when completing complex neuropsychological tasks, as well as support for the memory model, thus suggesting that this particular pattern of memory impairment occurs because encoding under narcosis produces a weaker memory trace than normal.Lastly, the study has a number of implications for industry. For example, divers need to compensate for slowed task completion by, firstly, planning more time to complete complex tasks, and secondly, by practicing those tasks prior to the actual deep dive (either on the surface or in shallow water). The need for using additional forms of recording of events or objects at depth, to aid memory encoding and subsequent recall at surface was also emphasised.

[发布机构] Stellenbosch University