MTOR and fragile X syndrome: The extracellular signal–related kinase (ERK) and mammalian target of rapamycin (mTOR) signaling pathways are required for the regulation of mGluR-LTD [29, 30] Studies have shown that antagonizing the mGluR pathway can alleviate the phenotypes of FXS [31] Therefore, mGluR theory provides new avenues for the understanding of pathological mechanisms and therapeutic intervention of FXS.