Enhanced visual memory effect for negative versus positive emotional content is potentiated at sub-anaesthetic concentrations of thiopental
Abstract
Emotional information has the ability to alter the formation and strength of a memory ('memory modulation'). Memory modulation by negative emotion is mediated by the amygdala. It is not known how gamma aminobutyric acid (GABA)ergic drugs affect the processes involved in memory modulation. This study investigates whether memory for negative emotional stimuli is more refractory to the effects of GABAergic drugs. Eighty-three healthy volunteers were shown a randomized sequence of 60 visual stimuli consisting of negative, positive and neutral emotive pictures, while receiving a controlled infusion of thiopental (n=31), propofol (n=31), dexmedetomidine (n=10) or placebo (n=11). After a 5 h retention interval, when drug concentration was negligible, subjects performed a recognition task with 'old' pictures randomly mixed with 'new' pictures. Drug effect was calculated as the proportionate reduction in recognition for images of each emotional valence. Forty-eight subjects were included in a within-subject logistic dose-response model analysis. In the thiopental group there was a smaller drug effect seen for negative vs positive images (proportional memory reduction from baseline 0.27 (SD 0.20) vs 0.56 (0.25), P<0.001, n=20 included in...Continue Reading
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