Phonetic measures of reduced tongue movement correlate with negative symptom severity in hospitalized patients with first-episode schizophrenia-spectrum disorders.

Background: Aprosody, or flattened speech intonation, is a recognized negative symptom of schizophrenia, though it has rarely been studied from a linguistic/phonological perspective. To bring the latest advances in computational linguistics to the phenomenology of schizophrenia and related psychotic disorders, a clinical first-episode psychosis research team joined with a phonetics/computational linguistics team to conduct a preliminary, proof-of-concept study.
Methods: Video recordings from a semi-structured clinical research interview were available from 47 first-episode psychosis patients. Audio tracks of the video recordings were extracted, and after review of quality, 25 recordings were available for phonetic analysis. These files were de-noised and a trained phonologist extracted a 1-minute sample of each patient's speech. WaveSurfer 1.8.5 was used to create, from each speech sample, a file of formant values (F0, F1, F2, where F0 is the fundamental frequency and F1 and F2 are resonance bands indicating the moment-by-moment shape of the oral cavity). Variability in these phonetic indices was correlated with severity of Positive and Negative Syndrome Scale negative symptom scores using Pearson correlations.
Results: A measure of variability of tongue front-to-back position-the standard deviation of F2-was statistically significantly correlated with the severity of negative symptoms (r=-0.446, p=0.03).
Conclusion: This study demonstrates a statistically significant and meaningful correlation between negative symptom severity and phonetically measured reductions in tongue movements during speech in a sample of first-episode patients just initiating treatment. Further studies of negative symptoms, applying computational linguistics methods, are warranted.
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