Electropalatographic study of connected speech in lateral misarticulation

Aim: Lateral misarticulation (LM) is a speech sound disorder in which air escapes laterally during speech. In LM speech therapy, errors often remain in conversational speech, even when single syllables are produced correctly. However, previous studies have used syllables, words, and phrases as speech samples and have not analyzed conversational speech. In this study, electropalatography (EPG) was used to observe tongue-palate contact patterns in a sentence that is similar to conversational speech and thereby clarify the articulatory dynamics of LM in connected speech. Methods: The participants included 30 patients with LM and 10 typical speakers. Tongue-palate contact patterns were recorded simultaneously with speech sounds. A global pattern (GP) for each participant was created by accumulating all the EPG patterns during the sentence production. The contact rates of cumulative global patterns (CGP) for each group were examined. Results: The GP for each participant revealed that typical speakers displayed continuous contact in the bilateral posterolateral region and less contact in the central region, whereas patients with LM exhibited less contact in the posterolateral region and more contact in the central region. The CGP for each group indicated that the LM group tended to have a lower contact rate in the posterolateral region and a higher contact rate in the anterior-central region than the typical group. Conclusion: Lateral bracing in the posterolateral region and groove formation in the central region are important for patients with LM to consistently produce correct sounds in connected speech.