Plasticity in the human speech motor system drives changes in speech perception

Area of Science:

• Neuroscience
• Speech Science
• Auditory Perception

Background:

• Speech motor learning is linked to auditory perceptual changes.
• The precise drivers of these perceptual shifts remain unclear.

Purpose of the Study:

• To investigate whether motor system changes or sensory inflow during speech learning drives auditory perceptual shifts.
• To determine the causal relationship between vocal sensorimotor adaptation and speech sound perception.

Main Methods:

• Subjects underwent a speech motor-learning task with altered auditory feedback.
• Two experiments utilized different auditory perceptual continua to test for perceptual changes post-learning.
• Speech production and perception were measured before and after the learning task.

Main Results:

• Auditory speech perception changed when motor learning adaptation shifted speech production into the perceptual test's phonetic range.
• No significant perceptual change occurred when auditory feedback during learning fell within the perceptual test's phonetic range.
• Central motor outflow, not just sensory feedback, was identified as the driver of perceptual shifts.

Conclusions:

• Changes in the speech motor system, specifically central motor outflow, are the primary drivers of altered auditory speech perception following vocal learning.
• This finding highlights the role of motor commands in shaping auditory perception, rather than solely relying on sensory input during learning.