Our findings suggest that PTN KO mice show an abnormal cognitive-behavioral phenotype characterized by perseverative tendencies indicative of cognitive rigidity; heightened anxiety; behavioral reticence in novel spatial or social contexts suggestive of neophobia; and microscopic neuroanatomical abnormalities including decreased neuronal area in layer IV, and neuronal hyperdensity in layers IV and V, of the lateral EC. This evidence concerns the gene PTN and Anxiety.