A method of determining whether a patient is deficient in spatial learning and memory. The method includes providing a sample from the patient, the sample containing an sgk gene product; and determining an sgk expression level in the sample. If the sgk expression level in the sample is lower than that in a sample from a normal person, it indicates that the patient is deficient in spatial learning and memory. Also disclosed are a method of identifying a compound for treating deficiency in spatial learning and memory and a method of treating such deficiency.