Fingolimod is a sphingosine-1 phosphate (S1P) receptor modulator and an immune modulator in use as a treatment for the remitting-relapsing form of multiple sclerosis. Hait et al. show that the active form of fingolimod can inhibit neuronal class I histone deacetylases (HDACs), modulate gene expression in the brain and facilitate memory extinction. The authors also show spatial and associative memory deficits in mutant mice lacking the enzyme necessary for formation of the active form of fingolimod.