Reason or emotion

" Cohen's clever trial went like this: he stuck people in an fMRI machine and made them decide between a small Amazon gift certificate that they could have right away, or a larger gift certificate that they'd receive in 2 to 4 weeks. Contrary to rational models of decision-making, the two options activated very different neural systems. When subjects contemplated gift certificates in the distant future, brain areas associated with rational planning (the Promethean circuits of the prefrontal cortex) were more active. These cortical regions urge us to be patient, to wait a few extra weeks for the bigger gift certificate.
On the other hand, when subjects started thinking about getting a gift certificate right away, brain areas associated with emotion - like the midbrain dopamine system and NAcc - were turned on. These are the cells that tell us to take out a mortgage we can't afford, or run up credit card debt when we should be saving for retirement. They are our impulsive pleasure seekers, the hedonists inside our head.
By manipulating the amount of money on offer in each situation, Cohen and his collaborators could watch this neural tug of war unfold. They saw the fierce argument between reason and feeling, as our mind was pulled in contradictory directions. Our ultimate decision--to save for the future or to indulge in the present--was determined by whichever region showed greater activation. More emotions meant more impulsivity. "

""the neurons that most strongly correlate with reward value in monkeys are not in the brain, they're the neck muscles as the monkey tenses before receiving a reward; but no one is going to argue that the neck muscles are "encoding" reward; (this isn't from any published studies, just personal communication with monkey physiology folks who do reward studies.)
* the midbrain dopamine neurons that encode reward value seem to be somewhat of a computational paradox, because the inputs that they receive from the visual system come from a brain area that only discriminates rough shapes of objects, so they can't possibly determine, from a computational standpoint, which object in the visual field is most rewarding.
All of this midbrain dopamine reward research stems from the original (and many, many, many subsequent) findings by Wolfram Schultz that led to the formation of the reward-prediction error hypothesis, that is, neurons in the substantia nigra (SN, in the midbrain) signal unpredicted rewarding events."

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