The long term stability of the place field of a pyramidal cell in a wild-type mouse and in a mutant mouse. Two simultaneous recordings from pyramidal cells in the hippocampus are illustrated in a wild-type mouse and a mutant mouse. In the wild-type mouse the spatial fields form and are stable when the mouse is taken out of the test environment and put back one hour later. When the wild-type mouse is taken out and put back 24 hours later, the field of the pyramidal cells are still quite stable. By contrast, in the R (AB) mice in which PKA has been compromised, the pyramidal cells form good fields and these are stable at one hours, but the fields are not stably maintained and are altered at 24 hours.