Behavioral and Neural Measures of Speech Motor Control
Phase: NA
Conditions: Speech
Sponsor: University of Wisconsin, Madison

Title: Behavioral and Neural Responses to External Alterations of Speech 
Variability (Exp 5) 
NCT number: NCT05286658 
Document date: 7/18/2023 
 
 

Study Protocol 
This study consists of three related behavioral paradigms aiming to test sensorimotor 
adaptation, a correlative analysis investigating the relationship between the outcome 
measurements from these three experiments, and several experiments seeking to modulate 
these outcome measures. Here we describe Experiment 5, which used 
magnetoencephalographic (MEG) imaging to will noninvasively measure auditory cortical 
activity evoked during speech production and playback. 
 
Experiment 5 specific Methods: In each of 3 separate sessions (order counterbalanced across 
participants), participants produce and listen to playback of the stimulus words ease, add, odd, 
and ooze (these contain the same four vowels as in Aim 1, but start without a consonant to 
avoid movement artifacts in MEG). We compare behavioral and neural responses induced by 
exposure to the perturbation field. 
• 
Baseline phase: 60 productions of each word to determine each vowel’s target (center of 
distribution in F1/F2 space) and to measure baseline variability and centering. These 
240 production trials will be interleaved with 240 perception trials where participants 
passively listen to speech audio recorded from production trials. 
• 
Exposure phase, Session A: inward-pushing perturbation field. A perturbation pushes 
each trial toward the vowel target measured in the baseline phase. The perturbation 
magnitude is 50% of the distance between the current production and the target. This 
effectively reduces the perceived error. 
• 
Exposure phase, Session B: outward-pushing perturbation field. A perturbation pushes 
each trial away from the vowel target measured in the baseline phase. The perturbation 
magnitude is 50% of the distance between the current production and the target. This 
effectively increases the perceived error. 
• 
Exposure phase, Session C: no perturbation is given. 
• 
Test phase: Identical to baseline phase. 
 
 
- 
MEG procedure: MEG data will be collected using a 306-channel, whole-head Elekta 
VectorView MEG system (Elekta Neuromag, Helsinki, Finland) located at the Medical 
College of Wisconsin, where Prof. Niziolek maintains an ongoing collaboration for MEG 
data collection. Participants will wear insert headphones and perform the speaking tasks 
described above. 
- 
Data analysis and outcome measurements: Behavioral outcome variables include 1) 
variability across trials in F1/F2 space (Fig 2C) and 2) centering, the reduction in 
variability from vowel onset to vowel midpoint. The MEG analysis measures participants’ 
auditory sensitivity to self-produced variability, as well as how this sensitivity is 
modulated by external manipulations to variability during the exposure phase. As in our 
past work, MEG sensor data from passive listening trials will be localized to its auditory 
cortical sources, yielding a peak source voxel in each hemisphere. From these peak 
voxels, the “virtual source” time-course will be estimated from the MEG sensor data in 
both speaking and listening trials constrained by each subject’s MRI. The dependent 
measure is the speaking-induced suppression (SIS), defined as the z-score reduction in 
average M100 amplitude in the speak condition compared with the listen condition. The 
M100 peak is defined as the peak activity between 75 and 150 ms after stimulus onset; 
peaks will be confirmed by visual inspection.  
- 
Sample size with power analysis: We planned to test 35 participants across the 3 
conditions; moving to a within-subjects design, we tested 15 participants in each of our 3 
conditions for a total of 45 scanning sessions. This provides a power of slightly over 0.80 

at α = 0.05 for detecting changes in variability (0.82, d = 0.44) and centering (0.81, d = 
0.43) observed in our behavioral data. Our previous MEG data investigating differences 
in within-participant SIS magnitude between different speaking conditions showed larger 
effects of d = 1.2 (mean z-score difference of 2.8). 
 
Statistical Analysis Plan 
Experiment 5: Behavioral outcome variables include 1) variability across trials in F1/F2 space 
and 2) centering, the reduction in variability from vowel onset to vowel midpoint. The MEG 
analysis measures participants’ auditory sensitivity to self-produced variability, as well as how 
this sensitivity is modulated by external manipulations to variability during the exposure phase. 
The dependent measure for sensitivity is the speaking-induced suppression (SIS), defined as 
the z-score reduction in average M100 amplitude in the speak condition compared with the 
listen condition. The M100 peak is defined as the peak activity between 75 and 150 ms after 
stimulus onset; peaks will be confirmed by visual inspection. We planned to test 35 participants 
across the 3 conditions; moving to a within-subjects design, we tested 15 participants in each of 
our 3 conditions for a total of 45 scanning sessions. Given our preliminary data, this provides a 
power of 0.82 at α = 0.05 (d = 0.44) for detecting differences in variability and a power of 0.81 at 
α = 0.05 (d = 0.43) for detecting differences in centering. Our previous MEG data investigating 
differences in within-participant SIS magnitude between different speaking conditions showed 
larger effects of d = 1.2 (mean z-score difference of 2.8).