The present invention provides a compound having a cholinergic muscarinic M1 receptor positive allosteric modulator activity and useful as an agent for the prophylaxis or treatment of Alzheimer s disease schizophrenia pain sleep disorder Parkinson s disease dementia dementia with Lewy bodies and the like. The present invention relates to a compound represented by the formula (I) or a salt thereof. (I) wherein each symbol is as described in the specification or a salt thereof.