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March 2014    Download the Entire Issue (PDF) Vol. 29, No. 3   RSS Feed for Undercurrent Issues
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The Perils of Deep Air Diving

how narcosis affects memory and thought processing

from the March, 2014 issue of Undercurrent   Subscribe Now

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As you know, scuba diving comes with associated risks, and nitrogen narcosis, i.e., getting "narked, "is one of them if you're diving on air. Increasing ambient pressure causes a form of intoxication in the brain, and the symptoms, a range of cognitive and motor deficits, start becoming apparent at depths below 100 feet.

One symptom of narcosis is memory loss, which research has shown results from impairment of longterm memory, rather than short-term, working memory. Studies have consistently shown that narcosis impairs free recall (such as words) but not recognition memory in depth ranges of 100 to 165 feet. One possible explanation is that narcosis disrupts the encoding process of breaking down the information into a form the person understands. Material is learned but the quality of encoding it is reduced, because the nervous system has a harder time memorizing -- and thus retaining -- the information, resulting in a weaker memory trace.

Testing a Hypothesis

Wendy Kneller and Malcolm Hobbs, psychology professors at the University of Winchester in England, tested the hypothesis that narcosis disrupts processing at the encoding stage. In a typical level of processing (LoP) task, research participants are presented with words to process either in a "shallow" manner (deciding whether the word is written in capital or lower-case letters, or whether it contains an "e"), or a "deep" manner (deciding whether the word fits into a particular sentence, or whether it's pleasant or unpleasant). If narcosis does affect the encoding of information, it's predicted that deeper processing learned under narcosis would continue to lead to better recall than shallow processing. In contrast, another hypothesis -- that narcosis impairs self-guided search, and the impairment rests in the ability to retrieve information, not on how well it was encoded -- then deep processing under narcosis shouldn't improve free recall....

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Important information that comes to
divers in deep waters may not be mentally
encoded properly, and may be lost
when it's important later in the dive.

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