npas2-deficient mice have been shown to have long-term memory deficits, suggesting that the protein may play a key role in the acquisition of such memories. this theory was tested by inserting a reporter gene (lacz) that resulted in the production of an npas2 protein lacking the bhlh domain. these mice were then given several tests, including the cued and contextual fear task, and showed long-term memory deficits in both tasks.