Studies have shown that individuals with sleep disturbance showed greater impulsivity. The hippocampus is not only a brain region important for memory which is consolidated during sleep, but also constitutes a part of brain network involved in decision making. Therefore, hippocampus may play an important role in linking between sleep disturbance and impulsivity. In the present study, we aimed to examine whether hippocampal activity moderates the relationship between sleep disturbance and impulsivity. 40 healthy participants (35.60 ± 10.81 years old, 53% male) without any sleep disorders based on nPSG completed a sleep-related picture task, which requires to view sleep-related and control pictures during a functional magnetic resonance imaging (fMRI) assessment using a 3T scanner. The Pittsburgh Sleep Quality Index (PSQI) and Barratt Impulsiveness Scale (BIS) were administered to assess sleep disturbance and impulsivity, respectively. The hippocampus, a region-of-interest (ROI), was defined based on the AAL atlas and hippocampal response to sleep-related pictures vs. control pictures was extracted. Moderation analyses were conducted using Hayes’ PROCESS macro in SPSS to test whether hippocampal response to sleep-related pictures moderates the relationships between sleep disturbance and impulsivity, controlling for age and gender. Results showed that the association between sleep disturbance and impulsivity was moderated by right hippocampal response to sleep-related pictures ( β=7.76, t=2.18, p=0.04). The sleep disturbance and impulsivity relationship was stronger when hippocampus activity was high ( β=1.75, t=2.29, p=0.03) compared to when hippocampus activity was low ( β=-0.71, t=-0.99, p=0.33) in response to sleep-related pictures. The current finding indicates that individuals with severe sleep disturbance may have high impulsivity when they show greater hippocampal activity in response to sleep-related pictures. This result suggests that the hippocampus may be an important brain structure for linking sleep disturbance and impulsivity. This work was supported by Brain Research Program through the National Research Foundation of Korea funded by the Ministry of Science, ICT & Future Planning (Study No.: 2016M3C7A1904338) and by the Ministry of Education (Study No.: 2018R1D1A1B07049704).

Objective: The purpose of this paper is to study the possible differences in clinical and polysomnographic findings, depending on the presence or absence of subjective complaints of abnormal sleep behavior, in patients with RWA on polysomnography. Method: We reviewed patient records and polysomnographic data of patients referred to the Sleep Laboratory at Seoul National University Hospital from June 1996 through October 2002. We defined the manifest RBD group (n=32) as patients having both complaints of abnormal sleep behavior and RWA on polysomnography. The latent RBD group (n=20) consisted of patients who exhibited RWA on polysomnography but did not complain of abnormal sleep behavior. The clinical characteristics and polysomnographic findings between the two groups were compared and analyzed. Results: Fifty-two subjects had RWA, as detected by polysomnography (42 males and 10 females, mean age of ). Subjects in the manifest RBD group were significantly older than those in the latent RBD group ( vs. , independent t-test, p