1. Quite secluded from sense desire, secluded from unskillful states -- one enters & remains in the first jhana: rapture & happiness born of seclusion, accompanied by thinking & examining. Quite secluded from the dopamine-based wanting system (substantia nigra), secluded from any other disturbing mental activity -- one enters & remains in the first jhana: norepinephrine system activation & opioid-based liking system activation born of seclusion, accompanied by background mental activity.

2. With the stilling of thinking & examining, one enters & remains in the second jhana: rapture & happiness born of concentration, unification of awareness free from initial thinking & sustained thinking -- internal tranquility. With the stilling of background mental activity, one enters & remains in the second jhana: norepinephrine system activation & opioid-based liking system activation born of concentration, unification of awareness free from background mental activity -- internal tranquility due to opioids flooding the nervous system.

3. With the fading of rapture, one remains in equanimity, mindful & clearly aware, and experiences happiness throughout ones being. One enters & remains in the third jhana, of which the Noble Ones declare, 'Equanimous & mindful, one has a pleasurable abiding.' With the fading of norepinephrine system activation, remaining equanimous, mindful & clearly aware -- with continued opioid-based liking system activation, one experiences happiness throughout ones being. One enters & remains in the third jhana, of which the Noble Ones declare, 'Equanimous & mindful due to opioid system activation, one has a pleasurable abiding.'

4. With the abandoning of pleasure & pain -- as with the earlier disappearance of elation & distress -- one enters & remains in the fourth jhana: mindfulness fully purified by equanimity, neither pleasure nor pain. With the abandoning of liking generated by opioid system activation -- as with the earlier disappearance of liking generated by dopamine system activation -- one enters & remains in the fourth jhana: mindfulness fully purified by the equanimity remaining from the prior opioid activation, a neutral state now that the liking systems have calmed down.