Immediate Effects of Vagus Nerve Stimulation on Human Cognition and Emotion

Vagus nerve stimulation is used for treating refractory epilepsy and major depression. This method has been shown to have a positive outcome in treatment on seizures in epilepsy, but its impact on human cognition remains unclear. The goal of this study was to study the immediate effects of vagus nerve stimulation on attention, cognition and emotional reactivity in patients with epilepsy.

This study included twenty patients (12 male and 8 female; 45 ± 13 years old) who were treated with VNS due to refractory epilepsy. Subjects performed a computer-based test of executive functions embedded with emotional distractors. During the test, their brain activity was recorded with electroencephalography. Subjects’ cognitive performance, early visual event related potential N1 and frontal alpha asymmetry were studied when cyclic vagus nerve stimulation was on and when it was off.

Our results show that vagus nerve stimulation improved working memory performance as seen in reduced error rate, OR = 0.63 (95% CI 0.47-0.85) and increased level of attention as seen in increased N1 amplitude [F(1, 15) = 10.17, p = 0.006]. In addition, vagus nerve stimulation modified brain's reactions to threat which was seen as longer reaction time [F(1, 16) = 8.23, p = 0.019] and greater frontal alpha asymmetry [F(1, 16) = 11.79, p = 0.003] in response to threat-related distractor

This is the first study to demonstrate immediate improvement in working memory performance in humans with clinically used vagus nerve stimulation. Moreover, vagus nerve stimulation had immediate effect on emotional reactivity shown in behaviour and brain physiology.