Voice onset time perception in Japanese aphasic patients

Area of Science:

• Linguistics
• Neurolinguistics
• Speech Science

Background:

• Aphasia, a language disorder resulting from brain damage, can affect speech perception.
• Voice onset time (VOT) is a crucial acoustic cue for distinguishing speech sounds, particularly in languages like Japanese.
• Previous research indicates that aphasic individuals may exhibit difficulties in processing various speech parameters.

Purpose of the Study:

• To investigate the ability of Japanese aphasic subjects to identify synthetic speech stimuli varying in voice onset time (VOT).
• To determine the extent of VOT identification impairment in this population.
• To explore the underlying reasons for any observed difficulties in VOT perception.

Main Methods:

• 17 Japanese individuals diagnosed with aphasia participated in the study.
• Participants were presented with synthetic speech stimuli ([ga] and [ka]) with systematically varied VOTs.
• Performance was assessed based on the accuracy of identifying the presented stimuli.

Main Results:

• Approximately two-thirds of the aphasic subjects demonstrated impaired performance in identifying the VOT of the synthetic speech stimuli.
• Analysis revealed that difficulties were not solely limited to labeling the sounds.
• Evidence suggests underlying issues in processing the acoustic and/or phonetic information of the speech stimuli.

Conclusions:

• A significant portion of Japanese aphasic subjects experience deficits in VOT identification.
• These deficits likely stem from challenges in both perceptual processing of acoustic-phonetic information and the categorization of speech sounds.
• Findings highlight the complex nature of speech perception impairments in aphasia.