People with brainstem stroke, advanced amyotrophic lateral sclerosis (ALS, also known as Lou Gehrig's disease), or other disorders can become unable to move or speak despite being awake and alert. In this project, the investigators seek to further translate knowledge about interpreting brain signals related to movement, and to further develop an intracortical brain-computer interface (iBCI) that could restore rapid and intuitive use of communication apps on tablet computers by people with paralysis.