This study is for infants and toddlers between 8 and 24 months old who use one arm and/or hand differently following a perinatal brain injury. This is a time when investigators think they can best help improve how the brain controls movement. Investigators are testing whether the combination of transcutaneous auricular vagus nerve stimulation (taVNS) with 40 hours of constraint-induced movement therapy (CIMT) can help infants move their weaker arm and hand better and make the brain pathways for movement stronger.