Say what you don’t mean: cognitive difficulties in Parkinson’s can worsen intelligibility
Reviewed by Anna Volkmer

Hypokinetic dysarthria, seen in 70–90% of people with Parkinson’s, causes reduced range of movement during speech production, reduced volume, rate, pitch and intelligibility. This study aimed to explore the role of higher cognitive function in speech production by asking 20 people with Parkinson’s to produce 28 statements with either congruent or incongruent emotional prosody, e.g. ‘I won the state lottery’ in a happy or sad tone. Masked judgements of emotional tone and acoustic measures of speech rate demonstrated that, whilst people with Parkinson’s were able to generate accurate tones as per task demands, their speech rate increased on incongruent tasks. The authors hypothesise that this is likely an indication that people with Parkinson’s cannot make speech-motor adjustments to manage the cognitive demands of this task. They suggest that it is the cognitive demands that increased risk of unintelligibility. A better understanding of this could allow for the development of appropriately targeted interventions.

Congruency and Emotional Valence Effects on Speech Production in Individuals with Parkinson’s Disease.
Hebert K, Ahn JS, Azmi H, et al.
SEMIN SPEECH LANG
2025;46(1):4–13.