Vagus Nerve Stimulation Modulates Neuronal Spike Field Phase Locking and Synchrony Cross Areas Associated with Facilitation of Decision-making in Rats

Vagal nerve stimulation (VNS) has been shown to enhance memory and cognitivefunctions in humans and rats. A preliminary study has shown that VNS could influencedecision-making in epileptic patients. Neuroimaging data using human subjects haveindicated a critical role for the prefrontal cortex and amygdala in selecting properactions and calculating the expected value of loss- or gain-related, outcomes. Publisheddata in rats suggested that the decision-making performances were relying on thefunctional integrity of the basolateral amygdala (BLA) and anterior cingulate cortex(ACC). In this project we establish a rat model to monitor the effect of VNS on decisionmaking using rat gambling task (RGT) and characterize the electrophysiologicalproperties of ACC and BLA activated by VNS.We will show that moderate VNS does not affect rat’s general activity. VNS immediatelyfollowing training sessions in RGT facilitates advantageous choices in rats thatperformed RGT. This animal study will provide evidence supporting the somatic markerhypothesis (SMH) that bioregulatory processes, including those that express themselvesin emotions and feelings (somatic states), do play a role in influencing decisions.Brain neuronal oscillations play a basic role in coordinated activity, the field potentialoscillations modulate local spike timing, and moreover, the theta band (frequenciesamong 4 and 10 Hz) has been acknowledged for a wide span of cognitive functions.Given the fact that synchronously discharging cells are more effective at drivingneurons at subsequent processing stages next we will perform multi-electrodesrecording of neural spike and local field potential (LFP) from neuronal ensembles inACC and BLA simultaneously with RGT in behavioral animal to explore the neuralmechanisms underlying the VNS-induced facilitation of decision making. First, we willidentify the plasticity in the BLA-ACC synapse and demonstrate that VNS enhancessynaptic transmission in this pathway. Then, we will clarify the spike field (thetaoscillation) coherence and phase locking in BLA and ACC. Finally, cross-correlationanalysis will show that VNS induces enhancements of synchronization between LFPsrecorded in ACC and BLA, in particularly, in the theta range, which is consistent with anincrease of neuronal communication between the two regions. Combination of multipleelectrophysiological recording with rat gambling task in behavioral models in vivo shouldfacilitate to identifying the putative mechanisms underlying the therapeutic VNS incognitive impairment.