Vowel Space Expansion Sensorimotor Adaptation

Behavioral and Neural Measures of Speech Motor Control

The purpose of this research study is to understand how the brain processes and controls speech in healthy people. The investigators are doing this research because it will help identify the mechanisms that allow people to perceive their own speech errors and to learn new speech sounds. 117 participants will be enrolled into this part of the study and can expect to be on study between 1 day (Experiment 1) and 4 weeks (Experiment 2).

Study Overview

• Status: Recruiting
• Conditions: Speech
• Intervention / Treatment: Behavioral: Exp 3 Speaking Task

Detailed Description

The overall study (Establishing the clinical utility of sensorimotor adaptation for speech rehabilitation) aims to understand how cognitive, perceptual, and motor processes are integrated in the control of speech movements. The investigators study how this complex skill is performed in healthy speakers to understand how this system functions, how this skill relates to the perception of speech, and what role different parts of the brain play in this process. Different studies look at how speech motor control is executed, maintained, and changed. Overall, the study will recruit 329 participants over the course of 5 years. Participants can expect to be on study for up to 4 weeks.

The entire study is composed of 8 experiments and 6 interventions. The present record represents Experiments 1-4: 1) Generalization of Vowel Space Expansion to Untrained Words and Vowels; 2) Retention of Vowel Space Expansion After Training in Multiple Sessions; 3) Vowel Space Expansion Training With Connected Speech, and 4)The Relationship Between Acuity, Variability, and Adaptation in Vowels. The paradigms in Experiments 1-3 all involve speech production under conditions of altered auditory feedback, while Experiment 4 is a correlative analysis that compares data from Experiments 1 and 2.

The Experiment 1 paradigm tests how the vowel space expansion induced by sensorimotor adaptation generalizes to untrained items in a single session. Participants will produce four training words (bead, bad, bod, and booed) under a vowel centralization feedback paradigm in which auditory feedback is altered, training them to produce these words with more vowel contrast. In addition to these trained words, eight test items will be produced in pre-training and post-training phases only. We will compare to measure how learning transfers across words that share the same vowel (test words: keep, cap, cop, coop) or whose vowels are intermediate to those of the trained words and which share consonants with the trained words (test words: bid, bud, bade, bode).

The Experiment 2 paradigm tests how the vowel space expansion induced by sensorimotor adaptation is retained over time. Participants will complete eight sessions of the vowel centralization sensorimotor adaptation paradigm over four weeks, producing four training words (bead, bad, bod, and booed) under conditions of altered auditory feedback that train them to produce these words with more vowel contrast. We will measure changes in produced vowels at the start of each session in a baseline phase to assess how much retained across days and weeks.

The Experiment 3 paradigm tests whether vowel space expansion can be evoked by a vowel centralization feedback paradigm applied to running speech (full sentences) rather than single words in healthy speakers. Participants will produce sentences from the Harvard corpus while their speech feedback is altered to centralize vowel feedback. The investigators will measure how working vowel space increases under this paradigm.

Experiment 4 is a correlative analysis which tests whether sensory acuity and speech production variability can predict magnitude of sensorimotor adaptation in interventions 1 and 2. Auditory acuity will be measured through a phoneme discrimination task in which vowel sounds are played to participants over headphones; somatosensory acuity will be measured through a tactile discrimination task in which participants report the orientation (horizontal or vertical) of the gratings on a plastic dome pressed lightly into the tongue. Speech production variability will be measured as the formant variability in the baseline phase of the sensorimotor adaptation experiments in interventions 1 and 2. These measures will be correlated with sensorimotor adaptation magnitude found in the prior interventions.

• Study Type: Interventional
• Enrollment (Estimated): 117
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Carrie Niziolek, PhD; Phone Number: 608-890-0192; Email: cniziolek@wisc.edu

Study Locations

• United States
  • Wisconsin
    • Madison, Wisconsin, United States, 53705
      • Recruiting
      • University of Wisconsin
      • Contact: Carrie Niziolek, PhD; Phone Number: 608-890-0192; Email: cniziolek@wisc.edu

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• English-speaking adults
• normal hearing and speech
• no history of stroke or neurological conditions

Exclusion Criteria:

• Native language other than English
• Any neurological disorders other than the disorder of interest
• Any history of hearing disorders
• Uncorrected vision problems that prevent participants from seeing visually-presented stimuli
• Significant cognitive impairments that prevent participants from carrying out the task or from giving informed consent
• Vulnerable populations (minors and prisoners)

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: Healthy Adult Speakers; healthy adult participants across the lifespan in three groups:18-35, 36-55, and 56+

Behavioral: Exp 3 Speaking Task; Participant will sit in front of a computer screen in a quiet room and to produce speech based on what is on the screen. Participant may see real words or nonsense words to read. Investigators may play sounds through headphones and ask the participant to repeat them. Participant speech will be recorded by a microphone. This task takes about one hour to complete.; Other Names: vowel space expansion

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Average Vowel Spacing (AVS) Measured as the Mean of Pairwise Formant Distances Between Vowels	AVS is a local measure of vowel spacing.	up to 1 hour (Exp 1,3); eight visits of 1 hour each over 4 weeks (Exp 2)
Quadrilateral Vowel Space Area (qVSA)	qVSA measures the area (in Hz^2) between the F1/F2 coordinates of the corner vowels. This is a global measure of working vowel space.	up to 1 hour (Exp 1,3); eight visits of 1 hour each over 4 weeks (Exp 2)
Intelligibility measured by Percent of words correctly identified by 5 independent transcribers	Intelligibility is a perceptual measure. Four repetitions of each spoken production from each adaptation phase, as well as the minimal-pair neighbors from the calibration phase, will be identified by all transcribers. Because intelligibility in healthy speakers is expected to be near ceiling, speech signals will be masked by speech-shaped noise and delivered at 72 dB over closed-ear headphones. Signal-to-noise ratio will be determined prior to testing as the ratio where, on average, 50% of stimuli in the calibration phase are correctly identified. Transcribers will be native English speakers with no history of neurological/hearing disorders who pass a pure-tone hearing test.	up to 1 hour (Exp 1,3); eight visits of 1 hour each over 4 weeks (Exp 2)
Auditory acuity is measured as the average just noticeable difference (JND) along 4 vowel formant continua	Auditory acuity is measured as the average just noticeable difference (JND) along 4 vowel formant continua: /i/-/ɪ/, /ɛ/-/æ/, /u/-/ʊ/, and /ɑ/-/ʌ/. Acuity will be measured at continua midpoint (across-category acuity) and at the four corner vowel endpoints (within-category acuity). JNDs will be measured through a 4-interval, 2-alternative forced choice task (AABA or ABAA) via a staircase procedure.	up to 1 hour (Exp 1,3); eight visits of 1 hour each over 4 weeks (Exp 2)

Collaborators and Investigators

• Sponsor: University of Wisconsin, Madison
• Collaborators: National Institute on Deafness and Other Communication Disorders (NIDCD)
• Investigators: Principal Investigator: Carrie Niziolek, PhD, University of Wisconsin, Madison

Publications and helpful links

Helpful Links

• Link to study record for experiment 5 [NCT05286658]
• Link to study record for experiment 7 [NCT05723575]

Study record dates

Study Major Dates

• Study Start (Actual): February 15, 2024
• Primary Completion (Estimated): June 1, 2026
• Study Completion (Estimated): June 1, 2026

Study Registration Dates

• First Submitted: January 22, 2024
• First Submitted That Met QC Criteria: January 22, 2024
• First Posted (Actual): January 31, 2024

Study Record Updates

• Last Update Posted (Actual): April 9, 2026
• Last Update Submitted That Met QC Criteria: April 8, 2026
• Last Verified: August 1, 2025

More Information

Terms related to this study

• Keywords: speech motor control; vocal learning
• Additional Relevant MeSH Terms: Behavior; Communication; Verbal Behavior; Speech
• Other Study ID Numbers: 2017-1128 Adaptation (Exp 1-4); A481800 (Other Identifier: UW Madison); 1R01DC019134-01A1 (U.S. NIH Grant/Contract); Protocol Version 10/31/2021 (Other Identifier: UW Madison)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No