  Adults who are minimally verbal with autism spectrum disorder (mvASD) have
pronounced speech difficulties linked to impaired motor skills. Existing
research and clinical assessments primarily use indirect methods such as
standardized tests, video-based facial features, and handwriting tasks, which
may not directly target speech-related motor skills. In this study, we measure
activity from eight facial muscles associated with speech using surface
electromyography (sEMG), during carefully designed tasks. The findings reveal a
higher power in the sEMG signals and a significantly greater correlation
between the sEMG channels in mvASD adults (N=12) compared to age and
gender-matched neurotypical controls (N=14). This suggests stronger muscle
activation and greater synchrony in the discharge patterns of motor units.
Further, eigenvalues derived from correlation matrices indicate lower
complexity in muscle coordination in mvASD, implying fewer degrees of freedom
in motor control.
