Noninvasive Thalamocortical Neuromodulation With Low-Intensity Focused Ultrasound for Persistent Developmental Stuttering

University of Michigan20 enrolled

Overview

This research is studying the use of low-intensity focused ultrasound (LIFU; a mild, noninvasive acoustic stimulation technique) in a small number of people to learn about its safety as a treatment for stuttering. LIFU is a small, safe sound signal that produces a gentle, pulsing flow of acoustic waves to help different parts of the brain communicate with each other. Researchers want to understand how the mild, non-invasive brain stimulation affects speech relevant brain areas, which may in turn affect speech fluency and speaking-related brain activity in people who stutter.

This study will investigate whether Low-Intensity Focused Ultrasound (LIFU; also known as transcranial ultrasound stimulation, TUS) targeting the ventral intermediate (VIM) nucleus of the thalamus can safely and feasibly modulate neural activity and improve speech fluency in adults with Persistent Developmental Stuttering (PDS). Adult participants with PDS will be recruited through community advertisements and from existing institutional research registries, including individuals who have previously participated in noninvasive neuromodulation studies and have consented to be re-contacted for future research. All participants will complete an informed consent process prior to any study procedures. This is a within-subject, sham-controlled study in which participants will attend multiple study visits. Study procedures include: (1) baseline behavioral and speech assessments; (2) magnetic resonance imaging (MRI), including structural imaging and diffusion tractography, to localize individualized stimulation targets; (3) functional MRI (fMRI) to assess brain connectivity; (4) neuronavigation-guided LIFU stimulation targeting the VIM thalamic nucleus; and (5) concurrent and pre/post behavioral tasks assessing speech production, reading, and rhythm perception. Participants will receive both active and sham LIFU stimulation in separate sessions. Aim 1 is to evaluate the safety, feasibility, and precision of individualized, MRI-guided LIFU targeting of the left VIM thalamus using neuronavigation and post-hoc acoustic simulation. Feasibility outcomes include targeting accuracy, protocol adherence, adverse event monitoring, and participant tolerability. Aim 2 is to characterize the acute neural and behavioral effects of excitatory VIM-LIFU relative to a passive sham condition (reverse direction of transducer; no stimulation) using a within-subjects, double-blind crossover design. Primary outcome is the change in speech fluency (stuttered syllable percentage). Secondary outcomes are motor inhibition (stop-signal reaction time), and beat-based rhythm discrimination (d'). Exploratory neural outcomes include pre-to-post changes in resting-state thalamocortical functional connectivity and task-based (stop-signal fMRI) connectivity between VIM and speech motor regions (IFG, STN, pre-SMA). Exploratory analyses will also examine whether baseline thalamocortical connectivity predicts changes in functional connectivity and behavioral outcomes following stimulation. The study is noninvasive and does not involve surgical procedures or implantation. Data collected will include neuroimaging, behavioral performance, and speech recordings. The results of this study will inform the feasibility and potential efficacy of noninvasive subcortical neuromodulation for PDS.

Interventions

High DC LIFUDEVICE

Stimulation parameters and target location. Stimulation will be delivered using the BrainSonix BXPulsar 1002 System (BrainSonix Corporation, Sherman Oaks, CA, USA). Sonication Parameters will be as follows. Fundamental frequency: 650 kHz; pulse repetition frequency: 10Hz; pulse duration: 100ms; DC: 70% (yielding pulse width of 70 ms); sonication duration: 30 s; inter-sonication interval: 30s; LIFU-ON epochs per block: 12 epochs (Jang et al., 2025). During active stimulation a total of 4.2 min stimulation will be applied across all LIFU-ON epochs. Both active and sham stimulation sessions will last \~12 mins each. The researchers will be targeting ventral intermediate nucleus (VIM) region of the thalamus for the active stimulation.

ShamDEVICE

Stimulation parameters and target location. Stimulation will be delivered using the BrainSonix BXPulsar 1002 System (BrainSonix Corporation, Sherman Oaks, CA, USA). Sonication Parameters will be as follows. Fundamental frequency: 650 kHz; pulse repetition frequency: 10Hz; pulse duration: 100ms; DC: 70% (yielding pulse width of 70 ms); sonication duration: 30 s; inter-sonication interval: 30s; LIFU-ON epochs per block: 12 epochs (Jang et al., 2025). During sham stimulation a total of 4.2 min stimulation will be applied across all LIFU-ON epochs. Both active and sham stimulation sessions will last \~12 mins each. The researchers will be reversing the direction of the transducer placed on the head such that no active stimulation will be applied to the participant's head. But the neuronavigation procedures (targeting VIM) and stimulation parameters will be kept identical such that the participant experiences the same procedure across active and sham conditions.

Eligibility

Sex: ALLMin age: 18 YearsMax age: 65 Years

Medical Language ↔ Plain English

Inclusion Criteria: * have normal language, hearing and cognition * speak English as their primary language * currently stutter * score at least 10 (very mild) on the Stuttering Severity Instrument (SSI-4) or exhibit greater than 3% stuttered syllables during at least one of the first 3 speech samples * have not receive any treatment for stuttering within the past year Exclusion Criteria: * History of seizures * Major medical or neurological illness (e.g., stroke, serious head trauma, brain infection, Parkinson's disease, etc.) * History of closed head injury with loss of consciousness (e.g., concussion) * Metal or electronic implants such as cochlear implants and pacemakers * Braids or other hair styling that prevents direct access to the scalp (if removal not possible) * Current or planned pregnancy * Any active, unstable, or inadequately treated psychiatric condition, including but not limited to psychosis, active major depressive episode, bipolar disorder with recent mood episode, or current suicidal ideation. * Current use of antipsychotic medications for treatment of a primary psychotic disorder or bipolar disorder; current use of mood stabilizers (e.g., lithium, valproate) or benzodiazepines. Low-dose adjunctive use of atypical antipsychotics (e.g., brexpiprazole, aripiprazole, quetiapine) for treatment-resistant depression or anxiety is not exclusionary if the participant's condition is stable per the existing ≥2-month stability criterion. * Any condition or medication that lowers seizure threshold, consistent with standard practice across non-invasive brain stimulation protocols. Note: participants who cannot undergo MRI may complete the other portions of the study. For participants who cannot undergo MRI can be targeted for LIFU stimulation using a standard T1 scan. Resting state fMRI measures taken before and after stimulation will also be omitted for these cases. But the behavioral and speech measures can still be completed to provide pre and post-stimulation variations.

Outcomes

Primary Outcomes

Percentage of stuttered syllables produced during speech sample

The study will calculate the percentage of stuttered syllables (out of total syllables) in two speech samples (one before LIFU and one sample after LIFU) per each stimulation session. Decreased stuttered syllables represents better outcomes (greater reduction in stuttering). Two samples are collected during session 1 and two samples are collected during session 2. An additional baseline sample is collected at the baseline session (on a separate day before the two stimulation sessions).

Time frame: Baseline, and immediately before and after LIFU stimulation during Stimulation Session 1 and Stimulation Session 2 (sessions occurring a minimum of 2 days apart and a maximum of 1 week apart), for a total of 5 assessments over an estimated 2-3 weeks.

Secondary Outcomes

Stop signal response time (SSRT)

The study will measure the Stop signal response time (SSRT) from the stop signal fMRI task (one before LIFU and one sample after LIFU) per each stimulation session. Two SSRT outcomes are collected during session 1 and two SSRT outcomes are collected during session 2. An additional baseline SSRT is collected at the baseline session (on a separate day before the two stimulation sessions). SSRT will be measured 5 times total.

Rhythm discrimination score (d')

The study will compare the rhythm discrimination behavioral task from before and after LIFU during both session 1 and 2 for a total of 4 measurements. This is measured by the signal direction measures d' that will be calculated to quantify perceptual sensitivity (d'). Apart from the stimulation sessions, the baseline session will also collect this measure. Thus, assessed 5 times in total, considering the baseline session and stimulation sessions 1 and 2.