Dissociation of value and confidence signals in the orbitofrontal cortex during decision-making: an intracerebral electrophysiology study in humans.

Some decisions, such as selecting a food item in a novel menu, are not based on rational norms, or on trained habits, but on subjective preferences. How the human brain makes these preference-based decisions is still debated in cognitive neuroscience. Classical models focus on the comparison mechanism that achieves the selection of the option with best expected value. Recent models suggest that estimates of option values are refined until reaching sufficient confidence in the considered choice. Neuroimaging studies in humans and electrophysiology studies in animals have gathered evidence that value and confidence estimates are both represented in medial and lateral regions of the orbitofrontal cortex (OFC). Here, we took advantage of electrodes implanted within the OFC of human patients with pharmaco-resistant epilepsy (14 women, 12 men) to investigate whether value and confidence estimates can be dissociated in electrophysiology activity recorded during preference-based binary decisions. The overall value (liking ratings summed over options) and choice confidence (selection probability of the chosen option) were identified in low-frequency (4-8 Hz) OFC activity. These value and confidence signals were time-locked to the decision, showed opposite signs of correlation and were recorded in separate sites. This pattern of results is not consistent with the simulations of an attractor neural network model implementing a comparison of option values. However, it is compatible with the notion of a neural network generating sparse representations of option values and choice confidence estimates, based on which decisions can be made. The orbitofrontal cortex (OFC) is known to play a critical role in decisions based on subjective preferences, such as choosing between food items in a menu. However, the information provided by the human OFC has remained elusive, due to limitations of neuroimaging techniques. Here, taking advantage of electrodes implanted in patients for clinical purposes, we present a rare dataset of electrophysiological activity recorded during preference-based decisions. Our analyses suggest that the OFC signals two distinct constructs on which decisions could be based: the subjective values of available options and the confidence in the intended choice.