Oct 1, 2022
[Original post: Unpredictable Reward, Predictable Happiness]
1: Okay, I mostly wanted to highlight this one by Grognoscente:
I think really digging into the neural nitty gritty may prove illuminative here. Dopamine release in nucleus accumbens (which is what drives reward learning and thus the updating of our predictions) is influenced by at least three independent factors:
1. A "state prediction error" or general surprise signal from PFC (either directly or via pedunculopontine nucleus and related structures). This provokes phasic bursting of dopamine neurons in the Ventral Tegmental Area.
2. The amount and pattern of GABAergic inhibition of VTA dopamine neurons from NAc, ventral pallidum, and local GABA interneurons. At rest, only a small % of VTA DA neurons will be firing at a given time, and the aforementioned surprise signal alone can't do much to increase this. What CAN change this is the hedonic value of the surprising stimulus. An unexpected reward causes not just a surprise signal, but a release of endorphins from "hedonic hotspots" in NAc and VP, and these endorphins inhibit the inhibitory GABA neurons, thereby releasing the "brake" on VTA DA neurons and allowing more of them to phasically fire.