Altered identification with relative preservation of emotional prosody production in patients with Alzheimer's disease

Abstract

Patients with Alzheimer's disease (AD) show cognitive and behavioral disorders, which they and their caregivers have difficulties to cope with in daily life. Psychological symptoms seem to be increased by impaired emotion processing in patients, this ability being linked to social cognition and thus essential to maintain good interpersonal relationships. Non-verbal emotion processing is a genuine way to communicate, especially so for patients whose language may be rapidly impaired. Many studies focus on emotion identification in AD patients, mostly by means of facial expressions rather than emotional prosody; even fewer consider emotional prosody production, despite its playing a key role in interpersonal exchanges. The literature on this subject is scarce with contradictory results. The present study compares the performances of 14 AD patients (88.4±4.9 yrs; MMSE: 19.9±2.7) to those of 14 control subjects (87.5±5.1 yrs; MMSE: 28.1±1.4) in tasks of emotion identification through faces and voices (non linguistic vocal emotion or emotional prosody) and in a task of emotional prosody production (12 sentences were to be pronounced in a neutral, positive, or negative tone, after a context was read). The Alzheimer's disease patients showed weaker performances than control subjects in all emotional recognition tasks and particularly when identifying emotional prosody. A negative relation between the identification scores and the NPI (professional caregivers) scores was found which underlines their link to psychological and behavioral disorders. The production of emotional prosody seems relatively preserved in a mild to moderate stage of the disease: we found subtle differences regarding acoustic parameters but in a qualitative way judges established that the patients' productions were as good as those of control subjects. These results suggest interesting new directions for improving patients' care.