The company Nervana claim that their new earphones and generator devices can stimulate the vagus nerve in the ear.
The proprietary left earbud [...] not only receives the left channel of the music signal at its speaker, it also receives the stimulation signal within the earbud material itself, to deliver electrical stimulation to the inside surface of the ear canal and, thereby, the Vagus nerve.
They claim this improves mood, balance and relaxation:
NERVANA signals electrically stimulate nerves that trigger pleasure producing neurotransmitters. Neuroscientists have known for decades that these compounds are responsible for sensations of happiness, infatuation, and enhanced mood.
There are no references on their website.
Is there any research to suggest that Nervana headphones are capable of this?