Objective: Investigate differences in spoken language content in Parkinson’s disease (PD) compared to older controls.

Background: Conveying information is a primary goal of communication. PD language has been described as less detailed and less informative by family members and by naïve listeners, when compared to healthy adults and to pre-PD states. Yet, few studies have systematically explored the information content of spoken language in PD.

Methods: Spontaneous language samples from 19 PD participants (M_age = 70.74, M_UPDRSmotor  = 30.26) and 19 healthy controls (M_age = 68.16) were collected using two parallel forms of a standardized picture description task. The two groups did not differ on standardized measures of speech intelligibility and speech rate. Dementia was ruled-out using DSM-IV criteria and the Dementia Rating Scale-2. We conducted Main Event analyses (Capilouto & Wright, 2005) to quantify the main ideas conveyed correctly and with sufficient detail relative to the actors, actions, and events portrayed.  Correct Information Units (Nicholas & Brookshire, 1993; CIUs) were used to quantify words used that were correct to the picture and conveyed unique information.

Results: PD and Control language samples were equivalent on all productivity measures: total words, total CIUs, speaking rate, and sample duration, all p’s > 0.05).  This suggests that statistically significant primary outcome effects were likely unrelated to motor-speech difficulties. For the Main Event analysis (% complete and accurate main events), there was a significant difference between PD (M = 18.28, SD = 19.95) and Controls (M = 31.06, SD = 18.74) F (1, 36) = 4.14, p < 0.50, η² = 0.10. However, for the lexical measure (% CIUs) there was no significant difference between PD (M = 77.11, SD = 8.33) and Controls (M = 78.68, SD = 5.60) F (1, 36) = .470, p > 0.50).

Conclusions: While non-demented individuals with PD used correct words to describe events (CIUs), they tended to produce language with fewer overall and less complete details (main events).  This is important because reduced main event informativeness has been reported as a marker of subtle and early cognitive decline in MCI and Alzheimer’s disease. These data underscore the value of discourse analyses in understanding cognitive-communication difficulties in PD, beyond motor speech impairments, and highlight the potential for informativeness measures as early markers of cognitive changes in PD.

References: Capilouto, G., Wright, H. H., & Wagovich, S. A. (2005). CIU and main event analyses of the structured discourse of older and younger adults. Journal of Communication Disorders, 38(6), 431-444. doi:10.1016/j.jcomdis.2005.03.005.

Nicholas, L. E., & Brookshire, R. H. (1993). A system for quantifying the informativeness and efficiency of the connected speech of adults with aphasia. Journal of Speech and Hearing Research, 36(2), 338-350.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/information-content-of-spoken-language-in-parkinsons-disease-without-dementia/