Targeted reactivation of emotional memories during sleep

University Of Massachusetts Amherst, Amherst MA

Investigators

Abstract

Emotional memories are stronger and longer-lasting than neutral ones. One reason for this may be that sleep, which is known to strengthen newly-formed memories, prioritizes those associated with emotion. Reactivation (i.e. re-instantiation) of the neural representation formed during learning is the predominant mechanism linked to sleep-based memory strengthening. However, it is currently unknown whether such reactivation applies to the strengthening of emotional memories, let alone whether this mechanism is enhanced or more effective for emotional memories. Furthermore, young adults sometimes show a negative memory bias; thus, sleep may especially strengthen negative memories in this population. This project investigates the role of sleep-based reactivation in strengthening emotional memories, whether reactivation has a stronger effect on emotional versus neutral memories, and the relative efficacy of reactivation of negative and positive memories. As such, this research has substantial implications for the fields of sleep science and affective neuroscience. With regard to public health, this work impacts the design of sleep-based interventions to manipulate emotional memories for improved mental health and well-being. Finally, this project has significant educational impact and contribute to diversity in STEM through involvement of multiple post-baccalaureate and undergraduate trainees from systemically underserved groups. The objective of this proposal is to determine the role of reactivation during sleep on emotional memory consolidation. The central hypothesis is that reactivation during sleep strengthens emotional memory and that reactivation is more effective for emotional (at least negative) memories than neutral memories. To test their hypothesis, the investigators selectively reactivate memories during sleep using targeted memory reactivation. In four experiments, participants encode emotional (either negative or positive) and neutral stimuli in the presence of odor cues. An odor corresponding to half of the emotional and neutral stimuli is re-presented during subsequent non-rapid-eye movement (NREM) sleep in order to selectively reactivate these stimuli. Groups wherein odors are re-presented during REM sleep or wake are included for comparison. Overnight and over-week memory change are compared between cued and non-cued stimuli and between emotional and neutral stimuli. Visuospatial and picture recognition tasks are used to test spatial and item memory, respectively. Polysomnography is used to monitor sleep and measure neurophysiological correlates of memory reactivation. This research accomplishes the following: elucidates mechanisms of emotional memory consolidation, including the contribution of different sleep stages; provide mechanistic insight into the negative memory bias observed in young adults; and inform whether sleep-based reactivation can be targeted to manipulate emotional memory to benefit mental health. Furthermore, executing this research increase diversity in STEM through training of students from underrepresented groups in science. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.