Impaired Speaking-Induced Suppression in Alzheimer's Disease

Area of Science:

• Neuroscience
• Speech Motor Control
• Cognitive Impairment

Background:

• Alzheimer's disease (AD) is a neurodegenerative condition characterized by cognitive decline and speech alterations.
• Speaking-induced suppression (SIS) is an auditory cortical phenomenon reflecting the accuracy of auditory feedback predictions during speech production.
• A state feedback control (SFC) model posits that SIS arises from the match between predicted and actual auditory feedback during speaking.

Purpose of the Study:

• To investigate the impact of Alzheimer's disease on the fidelity of auditory feedback predictions during speech.
• To examine speaking-induced suppression (SIS) in individuals with AD compared to healthy controls.

Main Methods:

• Utilized magnetoencephalography (MEG) to measure auditory cortical responses in 20 AD patients and 12 healthy controls.
• Quantified speaking-induced suppression (SIS) by comparing auditory cortical responses during speaking versus listening to recorded speech.
• Employed a linear mixed effects model to analyze differences in SIS between groups.

Main Results:

• A significant reduction in SIS was observed in AD patients around 100 ms post-stimulus compared to healthy controls (p=0.011).
• This reduction suggests that individuals with AD generate less accurate predictions of their auditory feedback during speech.
• The findings align with the SFC model's hypothesis that reduced SIS indicates prediction inaccuracies.

Conclusions:

• Alzheimer's disease is associated with impaired auditory feedback prediction mechanisms during speech production.
• Inaccurate auditory feedback predictions contribute to the speech and language abnormalities observed in AD.
• This study provides novel insights into the neural underpinnings of speech deficits in Alzheimer's disease.