The present invention provides a compound which has a cholinergic muscarinic M1 receptor positive allosteric modulator activity and may be useful as a medicament such as an agent for the prophylaxis or treatment of Alzheimer's disease, schizophrenia, pain, sleep disorder, Parkinson's disease dementia, Lewy body dementia and the like. The present invention relates to a compound represented by the formula (I) or a salt thereof. In the formula (I), each symbol is as described in the attached specification.