Genetic variation of PACAP is associated with hippocampal morphology and memory in humans. (a) Statistical maps of t-transformed hippocampal volume differences derived by optimized VBM of individuals homozygous for the G allele in SNP3 of the PACAP gene, relative to A-carriers, in all subjects, thresholded at P<0.05 (corrected) in coronal, sagittal and axial views. These data show bilateral significant hippocampal volume reduction in individuals homozygous for the G allele. (b) Lower visual associate memory I score in individuals homozygous for the G allele in SNP3 of the PACAP gene, compared to A-carriers, in the schizophrenia group. Means±s.d. are shown. VPAI, visual paired associates I. *P<0.05, compared with A-carriers.