In the early stage of cerebral ischemia, the expression of PSD-95 increased, which can enhance the transduction of glutamate excitatory signals overexpressed by NMDAR, and neuronal apoptosis; then with the prolongation of cerebral ischemia time, the level of PSD-95 decreased, which reduces the conduction of NMDAR in the learning and memory synaptic signaling pathway17. The gene discussed is DLG4; the disease is brain ischemia.