Administration of the beta-adrenoceptor blocker propranolol impairs the processing of facial expressions of sadness

Rationale: Noradrenergic processes within the amygdala have been implicated in the modulation of memory for emotional material. The amygdala has also been associated with the processing of facial expressions of emotion, particularly those of fear and sadness. However, the role of noradrenaline in the latter process is unknown. Objective: Therefore the present study examined the effect of an oral beta-blocker (propranolol, 80 mg) upon facial expression recognition in healthy volunteers. Methods: Facial expressions of six basic emotions, which had been "morphed" between neutral and each emotional standard, were used in the recognition task. Subjects completed this task both before and 1 h following either propranolol or a placebo. Control measures of choice reaction time and vigilance performance were also included to assess any non-specific effects of the drug upon alertness and speed. Results: The administration of propranolol, relative to placebo, specifically increased reaction time to identify facial expressions of sadness correctly, in the absence of changes in speed to recognise other facial expressions of emotion. Subjective ratings of mood and alertness as well as speed in the two control tasks were not altered by propranolol, arguing against an account in terms of general sedation. Conclusions: These data suggest that noradrenergic processes are not only involved in memory for emotional material but also in the evaluation of sadness from facial expression. The selective nature of this effect adds to evidence suggesting that the recognition of different expressions of emotion depends upon at least partly separable neural processes. A role for noradrenaline in recognising sadness in others has potential relevance for our understanding of disorders characterised by disturbances in emotional processing.