Authors:

Andrade, J., Munglani, R., Jones, J.G. & Baddeley, A.D.

Reference:

Year of publication:

1994

CBU number:

3057

Abstract:

This paper explores the changes in cognitive function which occur as someone ‘loses consciousness’ under anaesthesia. Seven volunteers attempted a categorisation task and a within-list recognition test whilst inhaling air, 0.2% isoflurane, and 0.4% isoflurane. In general, performance on these tests declined as the dose of anaesthetic was increased, and returned to baseline after 10 minutes of breathing air. A measure of auditory evoked responding termed ‘coherent frequency’ showed parallel changes. At 0.2% isoflurane, subjects could still identify and respond to category exemplars but showed impaired short-term memory function. Electrical stimulation at 0.4% isoflurane, intended to mimic the arousing effects of surgery, had a small, beneficial effect on performance. A mean of 63% of category exemplars were identified at this stage, but recognition memory for those exemplars was at chance on recovery. There was no evidence for learning of words presented at 0.8% isoflurane.