Acute hypoxia fails to influence two aspects of short-term memory: implications for the source of cognitive deficits

There has been considerable interest in the possibility that short-term memory (STM) plays a role in the cognitive deficits produced by hypoxia. Claims have been made that two aspects of STM are impaired, the storage of information and the speed of retrieval of information, but a close examination of the evidence reveals that the whole issue remains an open question. Each aspect was investigated in a separate experiment using well trained subjects who breathed low oxygen mixtures adjusted to control arterial oxyhemoglobin saturation between 64%-66%. Exp. 1 assessed storage capacity with the dichotic listening paradigm. Hypoxia degraded the accuracy of recall, but this was probably an impairment of auditory perception and there was no evidence that storage was impaired. Exp. 2 assessed retrieval speed with Sternberg's memory scanning paradigm. As expected, hypoxia increased reaction time, but this could be accounted for by the slowing of an early stage of perceptual processing. No evidence was found to indicate that stages involving either retrieval from STM or binary decision were slowed. We conclude that STM storage and retrieval are not directly affected by hypoxia, and propose that either direct or indirect slowing of the central executive of working memory may account for the cognitive deficits produced by this stressor.