Signatures of Value Comparison in Ventral Striatum Neurons

Abstract

The ventral striatum (VS), like its cortical afferents, is closely associated with processing of rewards, but the relative contributions of striatal and cortical reward systems remains unclear. Most theories posit distinct roles for these structures, despite their similarities. We compared responses of VS neurons to those of ventromedial prefrontal cortex (vmPFC) Area 14 neurons, recorded in a risky choice task. Five major response patterns observed in vmPFC were also observed in VS: (1) offer value encoding, (2) value difference encoding, (3) preferential encoding of chosen relative to unchosen value, (4) a correlation between residual variance in responses and choices, and (5) prominent encoding of outcomes. We did observe some differences as well; in particular, preferential encoding of the chosen option was stronger and started earlier in VS than in vmPFC. Nonetheless, the close match between vmPFC and VS suggests that cortex and its striatal targets make overlapping contributions to economic choice.

The description-experience gap in risky choice in nonhuman primates

“…Overall, B chose the risky option on 63.48% of trials (n = 879 trials), 95% CI [60.20,66.67]; J chose risky on 59.01% of trials (n = 966 trials), 95% CI [55.83, 62.13]; K chose risky on 63.80% of trials (n = 489 trials), 95% CI [59.37,68.07]; all three biases are significantly greater than indifference (P < 0.0001, binomial tests). This replicates earlier reports showing that monkeys are riskseeking for described gambles Seo & Lee, 2009;So & Stuphorn, 2010;Stauffer, Lak, Bossaerts, & Schultz, 2015;Strait et al, 2014;Strait et al, 2015).…”

Taste, olfactory, and food reward value processing in the brain

“…Consistent with this, some neurons in these striatal regions respond to the taste, flavor, and/or sight of food (Rolls et al, 1983d;Rolls and Williams, 1987;Rolls, 2014;Strait et al, 2015;Williams et al, 1993).…”

A Spotlight on Reward

“…The idea is that a neuron's firing rate refers to the relative value of the attended option (Lim et al, 2011, Krajbich et al, 2010, Strait et al, 2015, Blanchard et al, 2015. (Relative means that value is in proportion to the value of its alternatives.)…”

“…Similar results are observed in single neurons when options are presented asynchronously. When the first option appears, neuronal responses in OFC, in ventromedial area 14 (vmPFC), and in ventral striatum all encode its value and then, when the alternative appears, they encode the value of the alternative, relative to the first (Strait et al, 2015, Blanchard et al, 2015.…”

“…decision maker should reject it. If value representations are formatted to the attended option, then the ensemble firing rate of OFC can be said to embody the evidence in favor of selecting the attended option (Rich and Wallis 2016;Strait et al, 2015). And if that's the case, then economic choices are fundamentally a series of stopping problems.…”