A watermaze protocol to examine competition of two memory traces.

<p>(A) Rats learned two opposite hidden platform locations in a watermaze over two successive sessions (four blocks of two trials per block, separated by 7.5 h) with a probe trial (no platform) conducted 7 d later. (B) Over both sessions, the animals decreased their escape latency (F = 21.5, df 1.7/51, <i>p</i> < 0.001). (C) At the 7 d memory test, the animals swam on average above chance level across zones (striped bar; t = 2.45, df 26, <i>p</i> = 0.022), but the trend favouring recency was not significant (<i>p</i> > 0.7). (D) Each session was followed by either sleep or novelty + sleep deprivation (N + SD) in a counterbalanced design. (E) Example swim path at test, with platform location followed by sleep NW (black zone) and N + SD SE (white zone) and starting location NE (green arrow). Note: based on extensive observation of swim patterns in the watermaze, the zones were deliberately designed to include an area by the side walls adjacent to one or other platform. (F) Swim time in zone followed by N + SD dominates over that followed by sleep (t = 1.97, df 52, <i>p</i> = 0.054, Cohen’s d = 0.54, N + SD to chance t = 2.31, df 26, <i>p</i> = 0.03). N + SD = novelty with sleep deprivation, NW = northwest, SE = southeast, *<i>p</i> < 0.05 <i>t</i>-test to chance. Means +/- 1 standard error of the mean (SEM). All raw data available in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.2000531#pbio.2000531.s024" target="_blank">S1 Data</a>.