GPHN and Alzheimer disease: The present study was therefore undertaken to determine the anatomical E/I ratio in postmortem PCx from middle-aged subjects with AD (early-onset), Down Syndrome (DS), and normal controls without pathology, using fluorescence deconvolution tomography (FDT) to histologically assess the synaptic levels of two scaffolding proteins implicated in regulating synaptic E/I balance, the excitatory postsynaptic density protein 95 (PSD-95) and inhibitory postsynaptic protein gephyrin (GPHN) (see Yu and Delbas17).