Prosodic Impairment in Dementia: Review of the Literature

Objective: Prosody, an important aspect of spoken language, is defined as the emphasis placed on certain syllables, changes in tempo or timing, and variance in pitch and intonation. Most studies investigating expression and comprehension of prosody have focused primarily on emotional prosody and less extensively on supralexical prosody. The distinction is indeed important, as the latter conveys information such as interrogative or assertive mode, whereas the former delivers emotional connotation, such as happiness, anger, and sadness. These functions appear to rely on distinct neuronal networks, supported by functional neuroimaging studies that show activation of the right hemisphere, specifically in the right inferior frontal area during emotional detection. Conclusion: This review summarizes the studies conducted on prosody impairment in Alzheimer's disease and other dementias, with emphasis on experiments designed to investigate the emotional vs. the supralexical aspect of speech production. We also discussed the available tools validated to test and quantify the prosodic impairment.