Retrieval-induced forgetting under psychosocial stress: no reduction by delayed stress and beta-adrenergic blockade

Retrieval-induced forgetting (RIF) is the phenomenon that 'retrieval-practice', the repeated retrieval of a subset of initially learned material, can impair the recall of episodically related memories. Previous studies showed that RIF is eliminated when retrieval-practice is carried out under psycho-social stress, anxiety, or in negative mood. However, pharmacological manipulation by hydrocortisone did not eliminate the effect. This study investigated the effect of beta-adrenergic blockade on stress-induced modulations of RIF, addressing possible interactive effects of the glucocorticoid and sympatho-adrenomedullary systems. Participants learned categorized word lists and then received either 60 mg propranolol or a placebo. After 90 min they were exposed to the TSST. A third group did not receive any medication and performed a non-stressful control task with the same timing as the other two groups. Finally, all participants underwent retrieval-practice and final recall. Both TSST groups exhibited a stress-induced increase in cortisol-levels, and the placebo group also exhibited large increases in markers of sympathetic nervous system activity and more psychological distress at the time of retrieval-practice. Although, overall recall was poorer under stress, an overall RIF effect emerged irrespective of group and showed no clear modulation by stress with or without beta-adrenergic blockade. In previous demonstrations of RIF elimination by negative emotion, state induction and retrieval-practice followed very briefly after initial learning. Given that both the previous study of hydrocortisone effects on RIF and the present study used longer delays between learning and retrieval-practice, the possibility that stress effects on retrieval-practice eliminate RIF only relatively briefly after learning is discussed.