Introduction: Subjective judgment allows humans to make rapid decisions under novel scenarios in the absence of explicit rules to guide their selection, and plays a critical role in many social, legal and political arenas. The single-neuronal basis by which subjective judgments are made in humans, however, is unknown.
Methods: Ten human subjects undergoing DBS surgery gave informed consent to participate in our study. Using microelectrodes, we isolated single units in the dorsolateral prefrontal cortex (DLPFC) along the trajectory of the clinical target. Patients then completed a subjective judgment task, where they are presented with visual stimuli of seven different real-world scenes with varying levels of danger and asked to judge whether the scene is safe or dangerous. The spiking activity of DLPFC neurons were collected and single units were then spike-sorted and analyzed offline.
Results: We isolated 96 single units in ten patients. 44 units demonstrated significant task-modulation compared with baseline activity (before stimulus presentation). We find that while many neurons displayed biphasic responses that closely tracked the individual’s opposing decisions, another prominent and largely distinct group of neurons closely tracked the equipoise or ‘tipping-point’ between the opposing decisions independently of their objective report. Taken together, these neurons provided a remarkably accurate representation of the individual’s voting profile, while displaying little or no information about the actual motor response used to indicate their selections.
Conclusions: We identify a group of neurons in the DLPFC that encode subjective valuations in humans, and provide a novel understanding of how complex subjective judgments are computed at the single-neuronal and population-levels. Taken together, these findings may help elucidate how decisions making is represented in the human brain and provide new insight into how to treat individuals with higher cognitive disorders.
Patient Care: We hope that by better understanding the neurophysiology behind decision-making, we can improve therapies for patients suffering from higher cognitive disorders.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Discuss ways in which the DLPFC participates in decision-making, 2) Identify neuronal responses in the DLPFC to subjective valuations of danger