Newborns who are born premature or suffer brain injury at birth are at risk for motor problems that may cause weakness in reaching and grasping on one side of the body. In older children, therapists may use a hand mitt and restraint for the stronger arm, to encourage use of the weaker side, called constraint-induced movement therapy (CIMT). Even with the high intensity therapy of CIMT, it typically takes between 40-120 hours total treatment time for most children to improve their motor skills. A non-invasive form of nerve stimulation, transcutaneous auricular vagus nerve stimulation (taVNS), stimulates a nerve by the ear that enhances learning motor skills. The purpose of this study is to evaluate the safety and effectiveness of taVNS to improve motor skills when paired with CIMT in infants with one-sided weakness at 6-18months of age.