How do Alzheimer’s patients coordinate rhythmic gestures with singing voice?
Résumé
In Alzheimer’s disease, studies on bimodal language production (Carlamagno & coll., 2008) do not treat aspects of speech and gestures in a concomitant way. Supported by the results obtained from a case study (Caussade & coll., 2014), we made the hypothesis that Alzheimer patients’ communication disorders include a de-synchronization between speech and hand gestures. In this context, a protocol was elaborated to study the coordination between singing and hand gestures of patients with Alzheimer’s disease. The repetition tasks used in this protocol consisted in singing lallation on four melodies, and in four nursery rhymes. The songs were composed of 6 phrases with 8 syllables and a rhythm of one syllable per note. Each rhythmic gesture/beat was analyzed in terms of preparation phase and stroke to observe the temporal relationship between hand and singing rhythmic patterns. 20 French-native right-handed participants were recorded: 10 control participants paired by age and socio-educational level to 10 Alzheimer’s patients diagnosed with a MMSE score between 10 and 24 by our hospital partner. Professional musicians were excluded from the trial. Recordings were performed at the subjects’ home using two camcorders for front and profile views, and a lapel microphone. Preliminary results show patients made longer breaks than control participants, which is in line with Barkat-Defradas & coll. (2009), and thus their preparation phases of beats were longer, showing a de-synchronization between beats’ preparation phase and singing. Our results also show that both patients and control participants synchronize beats’ stroke at the peak intensity of the syllables, mostly with the syllable vowel nuclei which is coherent with French prosody (Crouzet & Angoujard, 2009). Lyrics in the nursery rhyme repetition tasks seemed to help both patients and control participants to repeat the melody with better accuracy than lallation, and more specifically to sing the good number of notes.