Participants:	100 healthy participants (aged 18–25)
Type of Study:	Read-aloud Tasks
Location:	Hong Kong
Media type:	audio
DOI:	N/A

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Project Description

This study aims to examine the modulatory effects of High-Definition Transcranial Direct Current Stimulation (HD-tDCS) on speech motor learning by targeting two brain regions: the Broca’s area and the inferior parietal cortex. These two regions play critical roles in speech sensorimotor integration, motor planning, and error monitoring. By delivering a weak direct current through the scalp and skull to a specific cortical region using a 4×1 HD-tDCS montage, HD-tDCS can transiently increase (anodal) or decrease (cathodal) cortical excitability. Therefore, stimulation of these two regions is expected to modulate speech motor learning efficiency and short-term retention in healthy adults.

A total of 100 healthy participants (aged 18–25) were recruited for the study. All participants were randomly assigned to one of the following five groups: (1) anodal HD-tDCS over Broca’s area, (2) anodal HD-tDCS over the inferior parietal cortex, (3) cathodal HD-tDCS over Broca’s area, (4) cathodal HD-tDCS over the inferior parietal cortex, and (5) sham HD-tDCS. The group allocation and stimulation condition were double-blinded, such that neither the researcher administering the stimulation nor the participant was aware of the assigned condition.

For groups (1)–(4), continuous stimulation at 2.0 mA was delivered for 20 minutes. For group (5) the sham condition, 30 seconds of stimulation was delivered at the beginning and end of the session to mimic the tingling sensations associated with active stimulation, and no active current was delivered during the remaining stimulation period.

Participants completed a speech motor learning task at three time points: (A) before HD-tDCS (baseline), (B) during HD-tDCS (online learning phase), and (C) 4 hours after HD-tDCS (delayed retention phase). Parts (A) and (B) were conducted in a single session lasting approximately 1 hour. A 4-hour interval was included to assess short-term consolidation effects, after which part (C) was administered and lasted approximately 15 minutes.

The task consisted of 20 target tongue twisters and 20 filler tongue twisters. The 20 target tongue twisters included 10 contextualized and 10 de-contextualized forms. The de-contextualized versions were derived from the contextualized forms by systematically altering the initial consonants to increase articulatory competition and sequencing demands. The filler tongue twisters were also divided into 10 contextualized and 10 de-contextualized items; however, only 10 filler items were randomly selected by the software for each session to reduce predictability and minimize practice effects.

• Information on participant characteristics is in this spreadsheet.
• The sentence list is in this spreadsheet.
• Jyutping versions of the sentences is in this table.

This dataset is currently under embargo.

Acknowledgements

Christy Sze Wai Cheung helped with the manual correction of the transcripts.