Asymmetric functional connectivity is not specific to reward-related task activity in OFC

Hemispheric asymmetry in functional connectivity of the orbitofrontal cortex (OFC) has been recently demonstrated in reward-related cognitive tasks like gambling. In this work, which was part of our Neuromatch Academy 2022 project, we used resting state and task-dependent fMRI data from 339 human subjects from the Human Connectome Project (HCP 2020) to quantify the asymmetry of functional connectivity between left and right OFC, and posterior OFC (pOFC) regions during rest and task blocks. We then aimed to relate this asymmetry index (AI) to reward-driven impulsivity traits, quantified by subjects’ mean response times during a gambling task. We first identified sets of brain regions showing significant functional connectivity with left, and right OFC and pOFC regions during resting state across the group of subjects. This revealed 320 regions for right OFC, 308 for right pOFC, 296 for left OFC, and 241 for left pOFC spread across both hemispheres. We quantified the hemispheric asymmetry of each of these four regions (left and right OFC, pOFC) during gambling task, and in a task involving fearful or neutral stimuli. We found that left OFC, and pOFC showed a significantly higher AI during gambling task relative to resting state, but not their counterparts on the right hemisphere, replicating earlier reports of hemispheric asymmetry in the functional connectivity of OFC during gambling task. This asymmetry was comparable between reward and punishment blocks of the gambling task. However, we found no relation between the AI and subjects’ mean response times during the gambling task suggesting that impulsivity traits in behavior is not driven by hemispheric asymmetry of OFC, and pOFC regions. Furthermore, we found that left OFC, and pOFC had significantly higher AI during a non-gambling task involving fearful or neutral stimuli compared to resting state, and the AI computed for these two tasks were comparable. Taken together, these results suggest that asymmetric functional connectivity of OFC regions is coupled to task performance but not necessarily to reward-driven impulsivity traits.