Passive avoidance test

This paradigm targets the ability of mice to behave in a contrariwise manner regarding their innate preference for dark areas as opposed to bright ones. Shuttle boxes were divided into two compartments separated by a guillotine door, one of which was kept dark while the other remained lit. The floor of the shuttle box consisted of electrified parallel metal bars. During the first phase, the mouse was placed in the brightly-lit area facing away from the entrance to the dark compartment. Upon entrance to the dark compartment, the guillotine door closed and the animal was administered a single inescapable 2 second 0.32 mA electric shock, following which the mouse was returned to its home cage. The animals were returned to the shuttle box 24 h later⁴⁵. Entrance into the dark compartment was detected by infrared sensors; signals from a mouse poking its head through the door were ignored unless the mouse fully entered into the dark compartment. No shock was administered during this phase. The latency to enter the dark compartment was automatically assessed by Coulbourn Instruments software (Graphic State 3.1). The trial was terminated following 15 min if the animal did not cross into the dark compartment. Group sizes consisted of the following: 7B2^+/+, n = 17; hAPP^tg7B2^+/+, n = 8; hAPP^tg7B2^+/−, n = 13; hAPP^tg7B2^−/−, n = 7. A two-way repeated measures ANOVA was performed for genotype and phase factors. This ANOVA was followed by the Holm-Sidak post hoc test.