A mental state is assumed to be stable depending on how long it remains in one state. If the mental state is stable, and consistent in reacting to stimuli, it means that a schema is activated in the brain, causing the reaction. According to several accounts, schemas correlate with the activities of neuronal assemblies, which are groups of coupled neurons. These neurons are connected to form an assembly. The connection between the neurons within the assembly is stronger than the connections between the neurons and the environment.