Padoa-Schioppa also found that other neurons in the OFC encode the value of only one of the two juices offered to the monkey. Some neurons encoded the value of the grape juice, while other neurons encoded the value of the apple juice. "The monkey's choice may be based on the activity of these neurons," says Padoa-Schioppa.
An important aspect of the results is that neurons in the OFC encode the economic value of offered and chosen goods independently of the particular way the goods are offered to the monkey, and independently of the specific action the animal uses to signal its choice. For example, OFC neurons encoding the value of apples and oranges would do so regardless of whether the apple is offered on the right and the orange on the left, or vice versa.
"This result has broad implications for possible psychological models of economic choice," says Padoa-Schioppa. "It suggests that economic choice is, at its essence, a choice between goods as opposed to a choice between actions--such as reaching to the right to take the apple or to the left to take the orange."
This work follows a paper published in February in the journal Cognition by Padoa-Schioppa with collaborators Lucia Jandolo and Elisabetta Visalberghi of the Italian National Research Council in Rome. That behavioral study found that monkeys indeed make choices by assigning values to available foods. In the present study, Padoa-Schioppa and Assad identify the neurons in the OFC that correlate such values.