The effects of vagus nerve stimulation on decision-making

Subcortical and brainstem structures are increasingly becoming recognized as important contributors to higher cognitive functioning. Decision-making is one such function, particularly as viewed within the framework of the somatic marker hypothesis (SMH). The SMH views the participation in decision-making by the body proper as integral to emotional biasing and hence key to choosing in an advantageous manner. This study focuses on the vagus nerves as a possible conduit for somatic afferent signals pertinent to decision-making. We tested eight epileptic patients with implanted left vagus nerve stimulators. To assess decision-making we used the gambling task, which is sensitive to real-life decision-making deficits. Using a counterbalanced design, each participant performed the gambling task under a condition in which low-level vagus nerve stimulation (VNS) was covertly delivered, and another condition in which no VNS was delivered. Participants showed improved performance, that is, made more advantageous choices, in the stimulated relative to the unstimulated condition. Although these results should be viewed as preliminary, they suggest that the vagus nerve is a conduit for afferent somatic signals that can influence decision-making.