Noninvasive Neurostimulation to the Inferior Frontal Sulcus or Cerebellum Improves Accuracy But Not Timing in a...

Area of Science:

• Neuroscience
• Cognitive Science
• Speech Science

Background:

• Speech motor learning involves phonological working memory (left posterior inferior frontal sulcus - LpIFS) and motor learning (right cerebellum - RCbm).
• Understanding how to enhance the acquisition of novel speech sounds, particularly non-native consonant clusters, is crucial for language learning and therapy.

Purpose of the Study:

• To investigate the causal effects of transcranial direct current stimulation (tDCS) on speech production accuracy and learning of novel non-native syllables.
• To differentiate the roles of LpIFS and RCbm in speech motor learning by applying targeted stimulation.

Main Methods:

• 105 healthy young adults practiced novel pseudowords with non-native clusters.
• Participants received anodal tDCS to either LpIFS, RCbm, or sham stimulation.
• Speech production speed and accuracy were measured for trained and novel stimuli.

Main Results:

• Both LpIFS and RCbm stimulation improved overall speech accuracy compared to sham.
• Learning (trained vs. novel accuracy difference) was enhanced by tDCS to either LpIFS or RCbm, suggesting improved motor program acquisition.
• Speech production speed was not significantly affected by any stimulation condition.

Conclusions:

• Targeted neural stimulation of LpIFS and RCbm can enhance the learning of new speech motor programs, specifically for non-native sounds.
• Phonological and motor learning mechanisms contribute distinctly but synergistically to non-native syllable acquisition.
• tDCS shows potential as an intervention to improve speech learning outcomes.