Lexical boundary error analysis in hypokinetic and ataxic dysarthria

Area of Science:

• Speech-Language Pathology
• Neuroscience
• Linguistics

Background:

• Dysarthria, a motor speech disorder, often results in reduced speech intelligibility.
• Listeners' perceptual strategies may not align with acoustic information in dysarthric speech.
• Previous research indicates lexical boundary errors (LBEs) are a key factor in intelligibility deficits.

Purpose of the Study:

• To investigate the role of lexical boundary errors in differentiating intelligibility issues between hypokinetic and ataxic dysarthria.
• To analyze how listeners use acoustic cues to segment speech in the presence of dysarthric speech characteristics.
• To compare the perceptual challenges posed by the prosodic deficits in ataxic versus hypokinetic dysarthria.

Main Methods:

• Lexical boundary error (LBE) analysis was performed on listener transcripts.
• Speech samples from individuals with hypokinetic dysarthria, ataxic dysarthria, and normal controls were analyzed.
• Intelligibility (words-correct) and error patterns were compared across speaker groups.

Main Results:

• Hypokinetic and ataxic dysarthria groups showed similar overall intelligibility scores.
• Distinct patterns of LBEs were observed between hypokinetic and ataxic dysarthria.
• Listeners' segmentation of ataxic speech deviated more from predictions based on degraded normal speech compared to hypokinetic speech.
• Prosodic deficits in ataxic speech (e.g., syllabic isochrony, loudness variation) presented greater perceptual challenges than those in hypokinetic speech (e.g., rapid rate, monotony).

Conclusions:

• The pattern of lexical boundary errors provides insight into listener processing of dysarthric speech.
• Ataxic dysarthria's prosodic deficits, particularly those affecting syllabic timing and loudness, significantly impact speech intelligibility.
• Listeners' difficulties in segmenting ataxic speech suggest a mismatch between available acoustic information and perceptual strategies.