Talk abstracts > Sébastien Ballesta (Université de Strasbourg)

Economic choices between goods entail the computation and comparison of subjective values. Previous studies examined neuronal activity in the orbitofrontal cortex (OFC) of monkeys choosing between different types of juices. Three groups of neurons were identified: offer value cells encoding the value of individual offers, chosen juice cells encoding the identity of the chosen juice, and chosen value cells encoding the value of the chosen offer. The encoded variables capture both the input (offer value) and the output (chosen juice, chosen value) of the decision process, suggesting that values are compared within OFC. Value-encoding cells integrate multiple dimensions, variability in the activity of each cell group correlates with variability in choices and the population dynamics suggests the formation of a decision. However, it was unclear whether these neural processes were causally related to choices. Using electrical stimulation, we recently demonstrated that neuronal activity in the OFC is causal to economic choices. Low-current stimulation (25 µA) increased the subjective value of individual offers and thus predictably biased choices. High-current stimulation (>100 µA) disrupted both the computation and the comparison of subjective values, and thus increased choice variability. Weak electrical stimulation (5-15µA) of OFC specifically disrupts value comparison without altering offer values. Therefore, (1) choices are causally linked to the activity of offer value cells and (2) OFC contributes to value comparison, likely by a circuit inhibition cellular mechanism (not by mutual inhibition at the level of offer value). All together, these results support the idea of a causal chain linking subjective values encoded and compared in OFC to valuation and choice. However, the exact cellular mechanisms by which values are compared within OFC remains an open question to the field.