As a representative of acupuncture and nonpharmaceutical therapy, auricular acupuncture has been widely for the treatment of insomnia. Transcutaneous auricular vagus nerve stimulation is a combination of auricular point stimulation and vagus nerve stimulation. It can not only treat primary insomnia effectively, but also is noninvasive, painless, portable and economical.
The medial prefrontal cortex is a core region of default mode network, which is important for maintenance of sleep. However, the mechanism of transcutaneous auricular vagus nerve stimulation in alleviating primary insomnia remains to be clarified. In this study, we found that taVNS could not only effectively reduce the score of Pittsburgh Sleep Quality Index, but also decreased functional connection between the left medial prefrontal cortex and bilateral dorsal anterior cingulate gyrus as well as functional connection between the right medial prefrontal cortex and the occipital cortex in patients with primary insomnia.
Furthermore, the decrease in functional connection was positively correlated with the decline of sleep index score. Therefore, we proposed that treatment with transcutaneous auricular vagus nerve stimulation can improve sleep quality and prolong sleep duration in patients with primary insomnia by reducing functional connection within default mode network, functional connection between default mode network and salience network, as well as functional connection between default mode network and the occipital cortex. This may be one of mechanisms of transcutaneous auricular vagus nerve stimulation in treating primary insomnia.