Modulatory effects of emotion and sleep on recollection and familiarity

Growing evidence suggests that declarative memory benefits from the modulatory effects of emotion and sleep. The primary goal of the present study was to determine whether these two factors interact to enhance memory or they act independently of each other. Twenty-eight volunteers participated in the study. Half of them were sleep deprived the night immediately following the exposure to emotional and non-emotional images, whereas the control group slept at home. Their memory for images was tested 1 week later along the valence and arousal dimension of emotion with the remember-know procedure. As emotional events appear to gain preference during encoding, via the modulatory effect of amygdala on prefrontal and medial temporal lobe regions, conscious retrieval of emotional pictures (relative to neutral ones) was expected to be less disrupted by sleep loss. Results indicated that emotional images were more richly experienced in memory than neutral, particularly those with high arousal and positive valence. Even though sleep deprivation resulted in behavioral impairment at retrieval of both emotional and neutral images, results revealed that remember-based recognition accuracy and its underlying process of recollection for emotional images were less influenced by the lack of sleep (the mean difference between control and sleep-deprived subjects was around 40% higher for neutral images than for emotional images). Familiarity, however, was affected by neither emotion nor sleep. Taken together, these results suggest that emotion and sleep influence differentially the subjective experience of remembering and knowing and the underlying processes of recollection and familiarity through brain mechanisms probably involving amygdala- and hippocampo-neocortical networks respectively.