AβOs induce cognitive impairment in mice. A–C, Male Swiss mice received a single intracerebroventricular injection of 1, 10, or 50 pmol AβOs [or vehicle (VEH)] and were tested in the novel object recognition task 24 h (A), 7 d (B), or 14 d (C) after injection. Error bars represent means ± SEM of the time spent on the novel (black bars) or familiar (white bars) objects (n = 10 mice/group). *p < 0.05 (a statistically significant difference; one-sample Student's t test). D, Anti-AβOs (NU4) immunoreactivity in dot blots of hippocampal extracts from vehicle- or AβO-injected mice. Error bars represent means ± SEM (n = 3–5 mice/group). *p < 0.05 (statistically significant difference; Student's t test).