The purpose of this study is to find out what are the best settings for applying electrical nerve stimulation over the skin for the short-term improvement of hand dysfunction after a stroke. The ultimate goal is to some day design an effective long-term training program to help someone recovery their ability to use their hands and function independently at home and in society. In order to know how to apply electrical nerve stimulation to produce a good long-term effect on hand dysfunction, we first need to know how to make it work best in the short-term, and improve our understanding of for whom it works and how it works.We will use a commercially available transcutaneous electrical nerve stimulation (TENS) unit to gently apply electrical nerve stimulation over the skin of the affected arm. This is a portable, safe and easy to use device designed for patients to operate in their homes.