posterior parahippocampal gyrus posterior parahippocampal gyrus the posterior parahippocampal gyrus is a portion of the parahippocampal gyrus. posterior parahippocampal gyrusdetailsidentifierslatinpars posterior gyri parahippocampalisneurolex idbirnlex_1295anatomical terms of neuroanatomy it can show deterioration in alzheimer's disease.