Scopolamine induces impairments in the recognition of human facial expressions of anger and disgust
Recent psychopharmacological studies lend support to the notion of partially dissociable neuronal systems dedicated to processing specific emotions. For example, GABA-ergic enhancement after an acute dose of the benzodiazepine, diazepam, produces specific impairments in anger and fear recognition. However, it is unclear if these impairments are a general property of benzodiazepines and other drugs that produce a similar profile of neurocognitive impairment to benzodiazepines, such as the anticholinergic, scopolamine.
We investigated the effects of scopolamine and the benzodiazepine, lorazepam, on emotion-recognition accuracy.
A double-blind independent group design was used with 48 healthy volunteers to compare the effects of scopolamine and lorazepam with an inactive placebo on a commonly used emotion-recognition task. Control measures included an episodic memory task and subjective mood ratings.
Anger and disgust recognition accuracy was impaired after scopolamine. In contrast, lorazepam produced no impairment in emotion-recognition despite producing similar levels of sedation and anterograde amnesia to scopolamine.
Scopolamine-induced cholinergic hypofunction selectively impaired the recognition accuracy of disgust and anger facial expressions. The effects of scopolamine on emotion-recognition are similar to those found in Huntington’s disease patients. Furthermore, the impairments in anger and fear recognition previously observed with diazepam do not appear to be a general property of benzodiazepines. This suggests that alterations in emotional processing involving changes in the ability to recognize threat-related emotions (particularly, fear and anger) may not be a principal mechanism underlying anxiolysis or paradoxical aggression seen with benzodiazepines.
KeywordsEmotion-recognition Disgust Anger Scopolamine Anticholinergic Lorazepam Benzodiazepine
SK was in receipt of a Wellcome Trust International Travelling Research Fellowship. We would like to thank Rosa Hoshi and Celia Morgan for comments and helpful discussion about this manuscript.
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