Introduction: Impaired expression of emotion through tone, loudness, rate, and rhythm of speech (affective prosody) is common after right hemisphere (RH) stroke and impedes all social interactions.
Hypothesis: Abnormal patterns of acoustic features correlate with listener judgment of affective prosody and are associated with infarcts of specific RH gray and white matter regions.
Methods: Forty acute ischemic RH stroke patients had MRI DWI and described a picture within 48 hours of onset. Affective prosody of picture descriptions was rated by 21 healthy volunteers (1-7 scale). We identified acoustic features that correlated with listener ratings with Spearman correlations and with linear regression to identify independent predictors. A neurologist identified percent damage to each of 9 regions after co-registration of DWI to an atlas. We identified lesions associated with abnormalities in important acoustic features using logistic regression.
Results: Listener ratings of prosody correlated with duration of voiced segments divided by total duration of speech segments(DurV/Dur) (rho=0.63; p<0.00001) and Spectral Flatness (SF) (rho= -0.55; p=0.0002). Variability in listener rating was best accounted for by DurV/Dur, SF, pitch range, and fundamental frequency coefficient of variation (CoV) in both women (F (4,12) =6.58; p=0.0048) and men (F(5,18)=5.13; p=0.0056). The only feature independently associated with prosody rating after adjusting for other variables was DurV/Dur (p<0.0001) for women, and SF (p=0.007) for men. Low SF was predicted by sex, age, lesion volume, and percent damage to the 9 RH regions (X2=27; p=0.0081). Sex, lesion volume, damage to inferior frontal gyrus pars opercularis, inferior fronto-occipital fasciculus, superior longitudinal fasciculus (SLF), and uncinate were the only independent predictors. The same variables predicted CoV (X2=33; p=0.0005); age and damage to supramarginal gyrus and SLF were the only independent predictors. The same variables plus education predicted low DurV/Dur (X2=25; p=0.02).
Conclusions: Impaired emotional expression after RH stroke is due to changes in specific acoustic features caused by infarct in right pars opercularis or supramarginal gyrus, or associated white matter tracts.