EFFECTS OF LOW CONCENTRATIONS OF ENFLURANE ON PROBABILITY LEARNING

The effects of controlled subanaesthetic concentrations of enfluraneon learning behaviour and on ability to change previously developeddecision strategies were studied in 10 male volunteers, usinga probability learning task. Subjects were instructed to predicton each of 200 consecutive trials, whether a left or a rightlight would appear. The appearance of lights was pre-determinedby a set relative frequency unknown to the subject. The relativefrequency was automatically changed at the end of the first100 trials, from 8/10 lights in the left side to 4/10. It wasfound that enflurane at subanaesthetic concentration of 0.25%(end-tidal) slowed the rate of learning, and increased the numberof trials required for readjusting the prediction strategy tothe changed situation. ^*Present address (for correspondence): Aranne Laboratory ofHuman Neuropsychology, Department of Neurology, Hadassah UniversityHospital, Jerusalem, Israel.