Short-Term Total Sleep-Deprivation Impairs Contextual Fear Memory, and Contextual Fear-Conditioning Reduces REM Sleep in Moderately Anxious Swiss Mice.

Munazah F Qureshi,Sushil K Jha

doi:10.3389/fnbeh.2017.00239

Munazah F Qureshi, Sushil K Jha

Open Access

https://doi.org/10.3389/fnbeh.2017.00239

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Abstract

The conditioning tasks have been widely used to model fear and anxiety and to study their association with sleep. Many reports suggest that sleep plays a vital role in the consolidation of fear memory. Studies have also demonstrated that fear-conditioning influences sleep differently in mice strains having a low or high anxiety level. It is, therefore, necessary to know, how sleep influences fear-conditioning and how fear-conditioning induces changes in sleep architecture in moderate anxious strains. We have used Swiss mice, a moderate anxious strain, to study the effects of: (i) sleep deprivation on contextual fear conditioned memory, and also (ii) contextual fear conditioning on sleep architecture. Animals were divided into three groups: (a) non-sleep deprived (NSD); (b) stress control (SC); and (c) sleep-deprived (SD) groups. The SD animals were SD for 5 h soon after training. We found that the NSD and SC animals showed 60.57% and 58.12% freezing on the testing day, while SD animals showed significantly less freezing (17.13% only; p < 0.001) on the testing day. Further, we observed that contextual fear-conditioning did not alter the total amount of wakefulness and non-rapid eye movement (NREM) sleep. REM sleep, however, significantly decreased in NSD and SC animals on the training and testing days. Interestingly, REM sleep did not decrease in the SD animals on the testing day. Our results suggest that short-term sleep deprivation impairs fear memory in moderate anxious mice. It also suggests that NREM sleep, but not REM sleep, may have an obligatory role in memory consolidation.

Highlights

Sleep is believed to play a role in memory consolidation
The freezing response was significantly high during 0–2 min interval (p < 0.001, F(2,23) = 67.95), 2–4 min interval (p < 0.001, F(2,23) = 43.63) and 4–5 min interval (p < 0.001, F(2,23) = 15.60) on the testing day compared to the time matched interval on baseline and training days (Figure 2B).The stress control (SC) animals (n = 5) demonstrated a similar freezing behavior on the testing day
We have found that short-term sleep deprivation alters the consolidation of contextual fear memory in Swiss mice

Summary

Introduction

Sleep is believed to play a role in memory consolidation. Several studies have reported that sleep alteration soon after training induces memory deficit. Selective rapid eye movement (REM) sleep deprivation impairs the consolidation of spatial memories (Smith and Rose, 1996; Bjorness et al, 2005). Sleep induction on demand (by expressing the temperature-gated nonspecific cation channel in the neurons) soon after training, facilitates memory consolidation. Sleep can play a role in synaptic renormalization. Learning-mediated up-scaled synaptic potentiation in the brain during wakefulness is renormalized during sleep for the homeostatic balance (Bushey et al, 2011). All these suggest that sleep serves a facilitatory role in memory strengthening and stabilization. Remains an intriguing question that if one learns more, would there be a more demand for sleep?

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