Reconsolidation of a reactivated memory can be altered by stress hormone levels.

Stern's summary in Science Magazine of work by Antypa et al.:

Reactivation of a memory can make it malleable to subsequent change during reconsolidation. Targeted pharmacological and behavioral manipulations after memory reactivation can modulate reconsolidation and modify the memory. Antypa et al. investigated whether changes in stress hormone levels during sleep affected later memory of a reactivated episode. The authors recited a story accompanied by a slide show to a group of male and female subjects. If subjects were given treatment to block cortisol synthesis during early morning sleep, then their 3-day-old memory of the story was more precisely recalled than if the early morning cortisol spike was uncontrolled. However, this improvement only occurred if the subjects had been given a visual cue for the story just before anti-cortisol treatment.