BDNF and major depressive disorder: We can observe that the outcomes studied were the effects of VNS on the rehabilitation of upper limb motor function; cognitive or sensory rehabilitation and emotional responses; effects of VNS on swallowing function; safety and feasibility of the VNS application; gait in subacute post-stroke; level of depression; daily life function and serum levels of CREB1, BDNF, and 5-HT; and comparison of active VNS paired with rehabilitation versus sham stimulation paired with rehabilitation.