Arousal-mediated memory consolidation: Role of the Medial Temporal Lobe in Humans

Although the influence of emotional arousal on declarative memory has been documented behaviorally, the mechanisms underlying arousal-memory interactions and their representation in the human brain remain uncertain. One route through which arousal achieves its effects on memory performance is by regulating consolidation processes. Animal research has revealed that the amygdala strengthens hippocampal-dependent memory consolidation in a limited time window following participation in an arousing task. To examine whether this integrative function of amygdalo-hippocampal structures extends to the human brain, we tested unilateral-temporal-lobectomy patients on an adaptation of a classic paradigm in which levels of physiological arousal at encoding modulate retention over time. Subjects rated emotionally arousing (taboo) and neutral words on an arousal scale while their skin conductance responses (SCRs) were monitored. Recall for the words was assessed immediately and after a 1-hr delay. Both temporal-lobectomy patients and control subjects generated enhanced SCRs and arousal ratings for the arousing words at the time of encoding. However, only control subjects exhibited an increase in memory for the arousing words over time. This group difference in the effect of arousal on the rate of forgetting suggests that the role of medial temporal lobe structures in memory consolidation for arousing events is conserved across species.