Mapping the Effects of Intracranial Electrical Stimulation of the Human Orbitofrontal Cortex.

Abstract

Introduction: Prior findings on direct intracranial electrical stimulation (iES) of the human orbitofrontal cortex (OFC), which includes the orbital and ventromedial prefrontal regions, have been mixed, with several reports lacking replication. We aimed to clarify the effects of iES in the OFC.

Methods: We analyzed data from 608 stimulations across 277 OFC site pairs (352 sites total) in 49 patients collected over 17 years of our practice.

Results: We found 24.4% of sites as responsive to iES, with subjects reporting visual and olfactory sensations. However, post hoc analysis revealed that these responses largely originated from the stimulation of nearby non-OFC optic and olfactory structures. After applying quality controls, stimulation of only 0.6% of OFC sites (2 sites, 2 patients) produced changes in subjective domain, while 99.4% had no reportable effects. Contrary to earlier studies, we found no evidence of valence lateralization or functional organization within the OFC.

Conclusions: Our findings suggest that the electrical perturbation of OFC is largely silent and does not lead to reportable change in the subjective state of the individual.

Significance: Orbitofrontal cortex is a higher transmodal cortical area. The variability and limited replicability of reported effects from prior publications and the inconsistencies in the extant literature about OFC stimulations can be attributed to methodological shortcomings.