Reading fluency in Spanish patients with Parkinson's disease: A reading prosody examination.

Abstract

The expressiveness during reading is essential for a fluent reading. Reading prosody has been scarcely studied in an experimental manner, owing to the difficulties in taking objective and direct measures of this reading skill. However, new technologies development has made it possible to analyse reading prosody in an experimental way. Prosodic patterns may vary, not being the same at the beginning of the reading learning process as in adulthood. They may also be altered in disorders such as dyslexia, but little is known about the prosodic characteristics and reading fluency of people with neurodegenerative diseases that cause language impairment, such as Parkinson's disease (PD). The aim of this work was to study reading fluency in PD considering the prosodic characteristics of its reading. The participants were 31 Spanish adults with PD and 31 healthy controls, aged 59-88 years. Two experimental texts were designed that included declarative, interrogative, and exclamatory sentences and experimental verbs and nouns. The manipulability level of the nouns and the motor content of the verbs were considered. The reading of the participants was recorded and analysed with Praat software. A longer reading duration and a greater number of pauses, especially in verbs, were found in the PD group, which also showed less pitch variation than the control group in the experimental sentences. The control group showed a big initial rise in declarative and interrogative sentences, as well as a stronger final declination in declarative and exclamatory ones, when compared to the PD group. The use of experimental methodologies for the analysis of reading fluency allows learning more about the prosodic characteristics of people with different pathologies, such as PD. Scarce pitch variability found in the analysis, together with the great number of pauses and the longer reading duration, leads to poorly expressive reading, which compromises fluency in PD. The exhaustive evaluation of the reading fluency of PD patients will make it possible to design more complete assessment methods that will favour the diagnosis and early detection of this pathology. What is already known on this subject • The speech of people with Parkinson's disease (PD) is often impaired by the appearance of hypokinetic dysarthria. The language of people with PD is usually affected with the progression of the disease, with lexico-semantic impairment which mainly affects verbs. Previous literature on reading fluency in PD usually considers reading speed and accuracy, neglecting prosody. Other neurodegenerative diseases with language impairment, such as Alzheimer's disease, commonly cause reading fluency problems. What this paper adds to existing knowledge • This study provides direct and objective measures of the reading fluency (speed, accuracy and prosody) in patients with PD, by the design of experimental texts. Reading fluency characteristics were found to be altered in these patients, especially in pitch variations and reading duration. The reading of Parkinson's patients showed a more flattened pitch. In addition, a greater number of pauses and longer reading durations were also found in the reading of verbs compared to the control group. What are the potential or actual clinical implications of this work? • The use of experimentally created texts makes it possible to analyse the influence of different psycholinguistic variables (frequency, length, motor content, manipulability) on reading fluency, and how the processing of these stimuli could be affected in PD. The objective analysis of the reading fluency characteristics in PD allows the design of more specific evaluation and diagnostic tasks. More complete assessment methods may allow the early detection of the disease. In the same way, it may favour a differential diagnosis with other neurodegenerative diseases.