Objective: We investigated action-verb generation in relation to cognitive function and motor severity in patients with Parkinson disease (PD).

Background: PD causes speech and language impairments, with defects in syntax, grammar and verb formulation. Action verb production may be particularly impaired and may reflect both motor and cognitive pathways. We evaluated action verb processing with a novel approach, through pauses before action verbs in semi-structured speech. We hypothesized that the duration of pauses before action verbs would be prolonged when compared with pauses before non-action verbs in PD and that action verb generation would be associated with cognitive function.

Methods: Digital recordings of non-demented PD (n=52) and healthy elderly controls (HC, n=28) participants describing the cookie theft picture or an alternative scene were analyzed with Praat software. Global cognition was assessed with MoCA. Pauses >1 second before action and non-action verbs were measured. Linguistic variables were compared in PD and HC groups with Mann-Whitney U test, then entered into a multivariate linear regression model, with dependent variable MoCA, controlling for age and motor severity.

Results: In the PD group, the mean number of action verbs used was 13.6 (SD 5.73), the number of pauses before action verbs was 0.36 (SD 0.72). There were no significant differences in pauses before action verbs or non-action verbs overall in PD compared to HC. However, PD patients generated fewer verbs relative to nouns when compared to HC (ratio of total nouns/total verbs (PD vs. HC) p=0.03). Global cognition was significantly correlated with total action verbs (r=0.40, p= 0.01), non-action verbs (r=0.46, p<0.01), and total nouns (r=0.33, p=0.02), though these associations were no longer significant in the multivariate model controlled for age and motor severity.

Conclusions: Non-demented PD patients displayed subtle deficits in verb generation in semi-structured spontaneous speech. Verb and noun generation correlated with global cognition. Our results support the further study of linguistic markers in PD, but pauses before action verbs will require further investigation to determine associations with motor and cognitive function in PD and with disease progression.

References: Syntax, action verbs, action semantics, and object semantics in Parkinson’s disease: Dissociability, progression, and executive influences.

Bocanegra et al, Cortex. 2015 Aug;69:237-54. doi: 10.1016/j.cortex.2015.05.022. Epub 2015 Jun 3.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/action-verb-generation-as-a-marker-of-cognitive-function-in-parkinson-disease/