The article doesn't spell it out, but it seems that's how dopaminergic stimulants make it hard to sleep. Dopamine deactivates the sleep circuit. This opens the

The article doesn't spell it out, but it seems that's how dopaminergic stimulants make it hard to sleep. Dopamine deactivates the sleep circuit. This opens the way to stimulants that doesn't impair sleep and the reverse. That could explain (partially unknown) modafinil's mode of action - a dri that works preferentially on the sleep neurons.