Spatiotemporal coupling of the tongue in amyotrophic lateral sclerosis.

PURPOSE The primary aim of the investigation was to identify deficits in spatiotemporal coupling between tongue regions in amyotrophic lateral sclerosis (ALS). The relations between disease-related changes in tongue movement patterns and speech intelligibility were also determined. Methods The authors recorded word productions from 11 individuals with ALS with mild, moderate, and severe dysarthria using an x-ray microbeam during word productions. A coupling index based on sliding window covariance was used to determine disease-related changes in the coupling between the tongue regions across each word. RESULTS The results indicated decreased spatiotemporal coupling of mid-posterior tongue regions and reduced tongue speed in the ALS-moderate subgroup. Changes in the range of tongue coupling relations and speed of movement were highly correlated with speech intelligibility. CONCLUSIONS These results provide new insights into the loss of lingual motor control due to ALS and suggest that measures of tongue performance may provide useful indicators of bulbar disease severity and progression.