Towards a typology of intonation in motor speech disorders

Intonational disturbances are known to play a major role in motor speech disorders (MSDs). Whilst detailed investigations were conducted to describe intonational deviances from a phonetic perspective, little attention has been directed towards classifying clinical intonation patterns from a phonological point of view. In addition, investigations have largely been based on structured speech tasks, providing little information on how findings translate into naturalistic speech behavior. Our study addresses this research gap, aiming to chart intonational profiles of and establishing typological similarities and differences between a variety of motor speech disorders including hypokinetic dysarthria (PD), ataxic dysarthria (AT) and foreign accent syndrome (FAS). Spontaneous speech samples of 20 speakers with MSDs (8 PD, 8 AT and 4 FAS) and 10 control speakers were analyzed in relation to inventory and prevalence of pitch
patterns as well as phrasing and accentuation using the autosegmental-metrical (AM) framework of intonational analysis. The results show that the MSD groups differed from the control group and from each other in 3 of the 4 aspects of intonation investigated, namely prevalence of pitch patterns, phrasing and accentuation. These findings indicate that the MSD groups investigated here present with clear typological differences allowing the charting of disorder-specific intonational profiles.