Stress and Sleep

Jan 22, 2013

An article in the June, 2011 issue of Sleep  helps us understand the impact that different kinds of stress have on sleep architecture. In this study Linghui Yang and colleagues trained mice with either a signaled escapable shock (SES), where they could move off of the shock grid, or a signaled inescapable shock (SIS), where the mice could not change the duration of the shock, which is the classic paradigm for the learned helplessness model of depression. Compared to SIS mice, SES mice showed significantly increased REM and significantly decreased NREM sleep. There were no differences found in the effects of the auditory cue alone after the initial training – both SES and SIS mice showed reductions in both NREM and REM sleep, a similar level of behavioral freezing, and similar increases in core body temperature. The auditory cue that preceded the shock appears to be processed differently than the contextual information associated with the SES and SES conditions. When we consider that REM sleep is associated with memory consolidation, these results suggest that inescapable trauma is less likely to be recalled even though the cue or trigger continues to evoke stress, one of the puzzling aspects of PTSD survivors, who frequently get triggered by cues before they can recall the trauma.

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