Prosodic expression and levodopa in Parkinson's disease

Abstract

Prosody is an important supra-segmental aspect of speech. Through prosodic variation, many cues regarding message intention, affected expression and type of interpersonal relationship are given to the listener. The main characteristics involved in prosody are fundamental frequency and loudness variability, speech rate, duration of pauses, vowel length, force of articulation and rhythm.Prosody pattern is an individual characteristic that requires an intact central and peripheral nervous system. It is highly influenced by biological factors, cultural features, personality traits, emotional states and aging. It is easy to understand that many neurological and mental disorders can produce a direct impact on prosodic expression. For example, maniacal episodes are vocally characterized by uncontrolled intensity and excessive frequency variability; on the other hand, vocal fold paralysis can severely limit frequency and loudness control, impairing the speaking and singing voice.Parkinson's disease (PD) patients suffer from reduction of the extent of all movements relating to speech, involving three subsystems: respiratory, phonatory and articulatory. In addition, swallowing may also be impaired 1 . Rigidity, bradykinesia and tremor are also present in oral communication, at several degrees of intensity that are not always directly related to the Hoehn and Yahr stages. PD patients' respiratory limitations do not provide proper breathing support for them to produce normal phrases and loudness variation; at the phonatory level, the vocal folds present reduced elongation, with restricted and unstable adduction impact on vocal quality and voice range profile; finally, at the articulatory level, speech sound imprecision and resonance imbalance contributes towards lower intelligibility scores. Patients with PD are usually characterized as presenting lower fundamental frequency (low pitch voice), monopitch and monoloudness (which gives the impression of a monotonous speech), phonoasthenia and lack of articulatory integrity 1 . The psychodynamics of individual with these characteristics are mostly negative: listeners may evaluate these patients as boring, unattractive and unhealthy, and even as having lower cognitive resources than their real condition permits 2,3 . Moreover, since message intelligibility may be reduced, misinterpretations due to the lack of sound precision and reduced intonation patterns will possibly decrease communicative interactions, lead to greater social isolation and limit quality of life 3 .Studies on voice and speech among PD patients, before and after treatment, frequently focus on the fundamental frequency and its variability and loudness levels in sustained vo wels or selected phrases 4,5 . Within this context, the paper published in this issue of Arquivos de Neuro-Psiquiatria by Azevedo et al. 6 adds an important attempt to assess prosody using several acoustic and temporal speech measurements. In addition to extracting 12 selected parameters relating to the oral communication impact of PD, the au...