Abstract: The present invention provides for a transgenic nonhuman mammal whose germ or somatic cells contain a nucleic acid molecule which encodes calcineurin or a variant thereof under the control of a regulatable promoter, introduced into the mammal, or an ancestor thereof, at an embryonic stage. The present invention also provides for a method of evaluating whether a compound is effective in improving long-term memory in a subject suffering from impaired long-term memory which comprises: (a) administering the compound to the transgenic nonhuman mammal of claim 1 wherein the mammal has increased brain-specific calcineurin activity due to expression of the nucleic acid, and (b) comparing the long-term memory of the mammal in step (a) with the long-term memory of the mammal in the absence of the compound so as to determine whether the compound is effective in rescuing the long-term memory defect in the subject.