Testing the core properties of the Brain Valuation System: an Intracranial EEG investigation
Dr. Alizee Lopez-Persem
Tuesday, 05 June 2018, 1pm to 2pm
Lecture Theatre, Plant Sciences
Hosted by Matt Apps
Estimating the value of alternative options is a key process in decision making. fMRI studies have identified a brain system, with the ventromedial prefrontal cortex (vmPFC) as a central component. Here, we examined the properties of this brain valuation system using a different recording technique, intracranial electroencephalography (iEEG), which offers direct access to the electrophysiological activity supposed to underpin hemodynamic responses, with much better temporal resolution. We recorded iEEG signals in 36 epileptic patients while they performed judgment tasks that involved rating different kinds of items (food, face, painting) and different features (age, likeability). We identified several brain regions in which High-gamma activity (50-150 Hz) positively correlated with likeability ratings, including not only the vmPFC but also the lateral orbitofrontal cortex (lOFC) and the hippocampus. Focusing on these three regions, we characterized the dynamics of value coding across time and frequency bands. Then we investigated their functional properties of valuation in the high frequency bands. All properties derived from fMRI results were replicated in the vmPFC: likeability ratings could be decoded in pre-stimulus activity (anticipation of value judgment), for both food and non-food items (generality), during both explicit and distractive tasks (automaticity), with both linear and quadratic functions (aggregation of value and confidence). Overall, our findings provide a bridge between two literatures on the neural underpinnings of subjective values: one based on electrophysiological studies in non-human primates and one based on fMRI studies in humans.