Semantic and logopenic primary progressive aphasia differ in pitch variation during a motor speech task

Abstract

AbstractBackgroundSemantic variant primary progressive aphasia (svPPA) is an uncommon neurodegenerative disease associated with selective atrophy of the dominant temporal lobe. Previous observations of left hemisphere damage suggest that prosodic expression (mediated predominantly by the right hemisphere and dorsal processing streams) is often preserved and may even be enhanced as a release phenomenon in some aphasic syndromes. We predicted left temporal injury would be associated with increased pitch variation, thereby distinguishing it from other PPA syndromes such as the logopenic variant of primary progressive aphasia (lvPPA).Method8 patients with svPPA and 10 patients with lvPPA repeated the syllable "Pa" as part of a motor speech evaluation. We compared the coefficient of variation of fundamental frequency, perceived as vocal pitch, using a separate variances two‐way t‐test. To better understand what may drive differences in pitch variation, we also correlated pitch variation with disinhibition measures on the Neuropsychiatric Symptoms Inventory Questionnaire (NPI‐Q) and the Frontal Assessment Battery (FAB).ResultCompared to 10 patients with lvPPA (M 4.5, SD 1.6), patients with svPPA (M 14.0, SD 10.3) displayed more variation of fundamental frequency (T = 2.6, p = 0.02). There was no correlation with either the NPIQ or FAB disinhibition measures.ConclusionPitch variation during simple motor speech tasks may serve as an additional diagnostic feature to distinguish between subtypes of PPA. The temporal atrophy associated with svPPA may release hyperprosodic performances on a simple motor speech task, through a mechanism beyond behavioral disinhibition as assessed in either the NPI‐Q or the FAB. Further research is needed to better understand the neural underpinnings of prosodic differences between PPA subtypes.