Number of earthquake and its intensity observed in the Tokyo area during the testing period for naive mice. ^*

*<p>The data relating to the earthquake were obtained from Japan Meteorological Agency. The earthquake greater than intensity scale 2–3 was not observed in this period.</p

Number of mice food consumption and its body weight.

<p>(A) Mean food consumption of 24 earthquake-experienced mice significantly increased after the main seismic event. Since mice were housed in groups of four per cage, mean food consumption was calculated per cage and was regarded as representative value for four mice housed in one cage. Error bars indicate S.E.M. (B) Mean body weight of earthquake-experienced (n = 24) and age-matched naive mice (n = 24). Black arrows in both figures indicate March 11, 2011, when the main seismic event of the Tohoku earthquake occurred. Note that x-axis represents weeks of age and that the data for age-matched naive mice were obtained before March 11, 2011.</p

Pavlovian fear conditioning using a weak training protocol.

<p>After conditioning, conditioned freezing to tone and context was sequentially measured in earthquake-experienced (n = 10), naive (n = 7), and non-conditioned naive mice (n = 6). (A) Tone-dependent short-term memory test was carried out 1 h after the conditioning. No differences were found among the three groups of mice before the presentation of the tone. However, the earthquake-experienced mice exhibited significantly higher freezing than non-conditioned naive mice during tone presentation. (B) Tone-dependent long-term memory examined 24 h after the conditioning. Conditioned freezing of earthquake-experienced mice was significantly higher than that of the other two groups of naive mice before and during the tone. (C) Context-dependent long-term memory examined 48 h after the conditioning. Conditioned freezing to context was higher in earthquake-experienced mice than in the other two groups of naive mice. †<i>p</i><0.10, *<i>p</i><0.05, **<i>p</i><0.01 compared with naive and/or non-conditioned naive mice. Error bars indicate S.E.M.</p

Number of earthquakes and its intensity observed in the Tokyo area.

<p>(A) Daily occurrence of earthquakes and its intensity observed in March, 2011. A major seismic event of the Tohoku earthquake occurred on March 11, 2011 (black arrow). On the day of the main seismic event, total number of 45 earthquakes were observed in the Tokyo area. (B) Daily occurrence of earthquakes and its intensity observed in April, 2011. Behavioral experiments for the earthquake-experienced mice were conducted between April 4 and 30 (dotted arrow). Classification of earthquake were according to the JMA seismic intensity scale.</p

Water chemistry data in the Tokyo area. ^*

*<p>The water quality in Maeno-cho, Itabashi, Tokyo, the water sampling point close to our institute. Inspection data for the water quality is obtained from the Bureau of Waterworks, Tokyo Metropolitan Government who routinely monitors the quality of water supply.</p>**<p>Standard values are for the water quality adequate for human consumption according to Japanese Law. cfu, colony-forming unit; nd, not detected.</p

Spatial memory testing in the Morris water maze task.

<p>Earthquake-experienced (n = 12) and naive (n = 6) mice under a dietary restriction schedule were trained until their performance reached asymptote. Dietary regimen and its duration were the same for both groups of mice. (A) Mean escape latency to platform during acquisition training. Earthquake-experienced mice found the escape platform significantly faster than naive mice from an early stage of training. However, the asymptotic escape latency of both groups of mice was equivalent. (B) Mean annuls crossings (upper) and mean quadrant time (lower) in the probe test. The probe test was carried out on the day after the completion of an 8-day training period. There were no significant differences in two indices of the probe test. Error bars indicate S.E.M.</p