Investigating Speech Sequencing in Neurotypical Speakers and Persons With Disordered Speech

Each trial of the training sessions will follow a simple reaction time protocol in which a nonsense syllable containing novel consonant clusters (e.g., GDADK) is produced as quickly and accurately as possible after an auditory prompt presented via earphones. During each training session, the participant will practice producing a set of 8 stimuli (the Fully Learned stimuli). Each of the 8 Fully Learned stimuli will be produced 60 times over the 6 training sessions.

Each trial of the training sessions will follow a simple reaction time protocol in which a nonsense syllable containing novel consonant clusters (e.g., GDADK) is produced as quickly and accurately as possible after an auditory prompt presented via earphones. During the training session, the participant will practice producing a set of 3 stimuli (the Fully Learned stimuli). Each of the 3 Fully Learned stimuli will be produced 60 times.

Each trial of the training sessions (total of 6 training sessions over 2 days) will follow a simple reaction time protocol in which a nonword stimulus formed by 2 or 3 syllables that are legal in American English is presented auditorily to the participant, who then produces the stimulus as quickly and accurately as possible. During training, each participant will repeatedly produce 6 nonwords, with each nonword produced a total of 60 times over the 6 training sessions.

Continuous anodal tDCS is delivered to a speech processing area of the brain during a 19-minute speech training session. The tDCS stimulation will ramp up to its maximum value (2 milliamperes) in the minute prior to the training session and maintained at that level throughout the session.

Sham tDCS stimulation is delivered to a speech processing area of the brain during a 19-minute speech training session. During the minute prior to training onset, the tDCS stimulator is ramped up to 2 milliamperes and then back down to 0.

Each trial of the training sessions will follow a simple reaction time protocol in which a nonsense syllable containing novel consonant clusters (e.g., GDADK) is produced as quickly and accurately as possible after an auditory prompt presented via earphones. During each training session, the participant will practice producing a set of 3 stimuli (the Fully Learned stimuli). Each of the 3 Fully Learned stimuli will be produced 120 times over the 8 training sessions.