PHF1 and Cognitive impairment: So in order to determine the effects of 7,8-DHF on levels of tau pathology of cognitive impairment ApoE-KO mice, we evaluated the alteration of abnormal tau by PHF1 antibody, which can recognize neurofibrillary lesions of brain with higher affinity for phosphorylation of tau at serine residues 396, and tau S396 antibody.