Adaptive and Individualized AAC

Inclusion Criteria: Control Subjects: * Adults and Children; \>12yo * Male or Female * All participants will be: (a) able to spell, (b) able to follow 2-3 step directions, (c) have functional vision sufficient to read 40 point text * No history of communication disorders; * No history of neurological disorders affecting speech or head movement. Subjects with SPI: * Adults or Children; age\>12yo * Male or Female * All participants will be: (a) able to spell, (b) able to follow 2-3 step directions, (c) have functional vision sufficient to read 40 point text, and (d) have a motor impairment that requires the use of an alternative access strategy to communicate and/or use technology. * Current or prospective AAC user with complex communication needs representing a broad spectrum of developmental and acquired SPI disabilities resulting from high spinal cord injury, chronic Guillain-Barré syndrome, brain stem stroke, cerebral palsy, locked-in syndrome, among others; * Sufficient head control and voluntary facial muscle activation (on the basis of clinical evaluation by Dr. Susan Fager and her team) to use the proposed wearable EMG/IMU sensor for the purposes of this study; * Evidence of at least partial voluntary head movement in at least 2 degrees of freedom (Individual differences in providing controlled movements of the head in various degrees of freedom due to their disease or trauma is not only acceptable but desirable); * Sufficient stamina and developmental maturity (on the basis of clinical evaluation by Dr. Susan Fager) to attend to the approximately 1-hour protocol outlined in Aims 1 and 3 without excess fatigue or distraction; * Availability for at least 3-4 testing sessions over the study period; * No medical or safety restrictions of active head and neck movement (as determined by Dr. Susan Fager in consultation with her clinical team); * Clinical evidence of preserved cognition by a score of 0 or 1 on NIHSS Consciousness and Communication item; * Ability to voluntarily blink eyes or raise eyebrows on command. Exclusion Criteria: Control Subjects * Non-English speaker; * Inability to follow simple instructions in English; * Restricted ROM of the head or neck; * Pain with head movement * Medical history of cardiac or respiratory complications, or disorders that would place the subject at risk for conducting the different motor activities; * Skin disorders that result in open lesions or hyper-sensitive/fragile skin on the forehead, preventing the use of medical-grade adhesive tapes to secure the sensors to the skin; * Unable to provide informed consent in English. Subjects with SPI * Non-English speaker; * Inability to follow simple instructions in English; * Medical history of musculoskeletal conditions (arthritis, spondylosis, etc.) that severely limit head movement or causes pain on head movement; * Restricted active or passive rotation of head and neck resulting from unstable vertebral, spinal cord, or nerve roots that places the subject at risk; * Medical history of cardiac or respiratory complications, or similar disorders that would severely reduce stamina and/or place the subject at risk for conducting the different motor activities; * Skin disorders that result in open lesions or hyper-sensitive/fragile skin on the forehead, preventing the use of medical-grade adhesive tapes to secure the sensors to the skin; * Unable to provide informed consent in English.