A positive allosteric modulator of the M4 muscarinic acetylcholine receptor; potentiates acetylcholine responses in CHO cells expressing M4 receptors (EC50s = 17.7, 630, and 1,000 nM for rat, human, and cynomolgus monkey receptors, respectively); selective for M4 over M1-3 and M5 receptors and a panel of receptors, transporters, and cation channels at 10 μM; reverses amphetamine-induced hyperlocomotion in rats from 3-56.6 mg/kg; reverses MK-801-induced hyperlocomotion, deficits in a pairwise visual discrimination task, and impairments in the acquisition of contextual fear conditioning in wild-type mice; increases freezing behavior in contextual and tone fear conditioning tests in wild-type mice when administered prior to the conditioning session from 3-30 mg/kg; reduces motor incoordination and prevents decreases in locomotion in the YAC128 transgenic mouse model of Huntington's disease at 10 mg/kg