Shows a proof of principle pilot study demonstrating the utility and impact of re-exposure to a CS of 3% CO₂ for 60 sec whenever three minutes of consolidated sleep occurred.

<p>(A) Demonstration of the learned bradycardic response to the CS of 3% CO₂ (similar to that shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0067435#pone-0067435-g004" target="_blank">Figure 4B</a>) that increased in magnitude across exposures; also, the US of footshock produced the expected tachycardic response. (B) Two sample tracings from a mouse showing a 60 sec exposure to 3% CO₂ during sleep with one event having no impact on sleep (left) and the other causing a distinct awakening (right). (C) The number of gas exposure events was averaged in two hour bins across the 24 hour re-exposure period for animals that were re-exposed to the CS+ (3% CO₂) compared to those re-exposed to the CS− (air). (D) The total number of awakenings across the 24 hour period after fear conditioning for animals re-exposed to the CS+ and to the CS−. (E) Time in REM sleep was averaged in two hour bins across the 24 hour re-exposure period for animals that were re-exposed to the CS+ and to the CS−. (F) Time in NREM sleep was averaged in two hour bins across the 24 hour re-exposure period for animals that were re-exposed to the CS+ and to the CS−.