Abstract
Vagus nerve stimulation (VNS) can enhance memory and cognitive functions in both rats and humans. Studies have shown that VNS influenced decision-making in epileptic patients. However, the sites of action involved in the cognitive-enhancement are poorly understood. By employing a conscious rat model equipped with vagus nerve cuff electrode, we assess the role of chronic VNS on decision-making in rat gambling task (RGT). Simultaneous multichannel-recordings offer an ideal setup to test the hypothesis that VNS may induce alterations of in both spike-field-coherence and synchronization of theta oscillations across brain areas in the anterior cingulate cortex (ACC) and basolateral amygdala (BLA). Daily VNS, administered immediately following training sessions of RGT, caused an increase in ‘good decision-maker’ rats. Neural spikes in the ACC became synchronized with the ongoing theta oscillations of local field potential (LFP) in BLA following VNS. Moreover, cross-correlation analysis revealed synchronization between the ACC and BLA. Our results provide specific evidence that VNS facilitates decision-making and unveils several important roles for VNS in regulating LFP and spike phases, as well as enhancing spike-phase coherence between key brain areas involved in cognitive performance. These data may serve to provide fundamental notions regarding neurophysiological biomarkers for therapeutic VNS in cognitive impairment.
Highlights
Utilized in human studies[14], most rats can learn to maximize their food reward by reasoning
We found that daily Vagus nerve stimulation (VNS), administered immediately following the training sessions of rat gambling task (RGT), resulted in increase in the number of ‘good decision makers’
At the beginning of RGT training two rats failed the test to induce a behavioral response by high intensity VNS stimulation which is a criteria of successful implantation of the cuff electrode
Summary
Utilized in human studies[14], most rats can learn to maximize their food reward by reasoning. Recent animal studies have shown that decision-making performances in the RGT depend on the integrated function of several sub-regions of the PFC, especially the prelimbic, cingulated and orbitofrontal cortices, and amygdala[18]. Several imaging studies of VNS, those using fMRI, have found changes in the PFC, orbitofrontal cortex, insula, anterior temporal poles and the hypothalamus[19,20]. These data suggest that VNS may be affecting areas of the brain involved in decision-making. The association between the locking of the ACC spikes to the phase of the theta oscillations in the BLA (cross-area spike-LFP-phase locking) following VNS was quantified
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