Encoding of multiple reward-related computations in transient and sustained high-frequency activity in human OFC
Saez, I, Lin J, Stolk A, Chang E, Parvizi J, Schalk G, Knight RT & Hsu M. Current Biology 2018.Abstract:
Human orbitofrontal cortex (OFC) has long been implicated in value-based decision-making. In recent years, convergent evidence from human and model organisms have further elucidated its role in representing reward-related computations underlying decision-making. However, a detailed description of these processes remains elusive, due in part to (i) limitations in our ability to observe human OFC neural dynamics at the timescale of decision processes, and (ii) methodological and interspecies differences that make it challenging to connect human and animal findings or to resolve discrepancies when they arise. Here we sought to address these challenges by conducting multi-electrode electrocorticography (ECoG) recordings in neurosurgical patients during economic decision-making to elucidate the electrophysiological signature, sub-second temporal profile, and anatomical distribution of reward-related computations within human OFC. We found that high frequency activity (HFA, 70-200Hz) reflected multiple valuation components grouped in two classes of valuation signals that were dissociable in temporal profile and information content: (i) fast, transient responses reflecting signals associated with choice and outcome-processing, including anticipated risk and outcome regret, and (ii) sustained responses explicitly encoding what happened in the immediately preceding trial. Anatomically, these responses were widely distributed in partially overlapping networks, including regions in the central OFC (Brodmann Areas 11 and 13) which have been consistently implicated in reward processing in animal single unit studies. Together, these results integrate insights drawn from human and animal studies and provide evidence for a role of human OFC in representing multiple reward computations.