Nature, 408, 982–985 (2000). The caption to Fig. 1 should have included the following statement: “Two transgenic mice vaccinated with Aβ consistently failed to make choices in the radial arm water maze during the 15.5 month testing period and could not be included in the statistical analysis. Thus the sample size is smaller for the behavioural studies performed at 15.5 mo than at 11.5 mo.”