The intensity frequency distribution for analysis of GPHN-ir at inhibitory synapses demonstrated that changes in AD and DS cases were similar to those of PSD-95-ir (Fig. 1f, h), with there being a marked reduction in the ratio of high-to-low levels of GPHN-ir per synapse in both layers 1 and 2, and stronger effects in layer 2 (Fig. 2e–h). Here, DLG4 is linked to Alzheimer disease.