neural circuitry.

Stuttering is characterized by intermittent speech disfluencies, which are dramatically reduced when speakers synchronize their speech with a steady beat.
The aim of the study was to understand the neural underpinnings of the "rhythm effect" in stuttering using functional magnetic resonance imaging (fMRI).

Participants: 16 adults who stutter (AWS) and 17 adults who do not stutter (ANS).
Procedure: Participants read sentences aloud in two conditions: normal (self-paced) and rhythmic (paced by beats).
Analysis: Activation and task-based functional connectivity analyses were used to compare neural responses between speaking conditions after controlling for speaking rate.

Participants who stutter showed fewer disfluent trials in the rhythmic condition than in the normal condition.
No significant changes in neural activation between conditions for the stuttering group, but greater activation was observed when groups were combined, particularly in:
- Areas associated with speech sequencing
- Sensory feedback control
- Timing perception
Increased functional connectivity among cerebellar regions during rhythmic speech compared to normal speech and decreased connectivity between the left inferior cerebellum and the left prefrontal cortex.

The connectivity modulation suggests that the fluency-inducing technique activates compensatory timing systems in the cerebellum, modulating top-down motor control and attention systems.
Findings support previous research linking the cerebellum to fluency in stuttering and highlight potential targets for therapeutic interventions.

Definition of Stuttering: A speech disorder impacting smooth articulation, affecting 1% of the population, characterized by repetitions, prolongations, and silent pauses accompanied by tension.
Stuttering can lead to social anxiety, reduced self-confidence, and impacts mental health (Craig et al., 2009).
Understanding stuttering could improve therapeutic interventions and quality of life for those affected.

Brain imaging studies have shown structural and functional differences in neural networks related to speech initiation and timing in individuals who stutter.
Individuals who stutter may have:
- Reduced activation in left hemisphere auditory areas.
- Overactivation in the right hemisphere areas typically not dominant for language processing.
Task-based connectivity studies indicate that stuttering arises not only from impairments in specific brain regions but also from disrupted communication between these regions.

The rhythm effect demonstrates that externally paced conditions can reduce disfluencies significantly.
Previous studies support that this fluency enhancement is robust, independent of auditory or visual pacing, and can be elicited by an imagined rhythm (Barber, 1940; Stager et al., 1997).
Pacing methods are proposed to enhance fluency by normalizing underactivation in speech production areas (Toyomura et al., 2011).

AWS: 16 individuals (Men: 11, Women: 5), aged 18-58 (M = 29.9, SD = 12.9).
ANS: 17 individuals (Men: 11, Women: 6), aged 18-49 (M = 28.7, SD = 8.1).
All subjects had normal hearing, speech, vision, and no history of neurological disorders except for AWS.

Speech Tasks: Participants read aloud 16 sentences from the Harvard Sentences set under two conditions:
- Rhythm Condition: Individual syllables paced by isochronous beats (1000 Hz, 25 ms duration).
- Normal Condition: Read at a natural rate.
Subjects practiced each sentence until proficiency was achieved.

MRI data collected in two locations: 3T Siemens Skyra scanner and 3T Siemens Prisma scanner.
Functional data were acquired using a BOLD imaging sequence aligned with speech tasks.

Analyzed disfluency rates and speaking patterns across conditions, finding significant differences in disfluency frequency and speech rate.
Stuttering significantly reduced in rhythmic conditions, with enhanced isochronicity measured by a lower coefficient of variation of intervocalic intervals (CV-IVIs).

BOLD responses modeled using a general linear model (GLM).
First-level contrast estimates were analyzed considering various covariates including motion and condition effects.

Seed-based functional connectivity examined using CONN toolbox, focused on cerebellar and cortical regions involved in speech production.
Connectivity showed significant differences between rhythm and normal conditions, highlighting the dynamic interaction between auditory, motor, and sensory regions.

The cerebellum plays a compensatory role in speech timing for AWS, reinforcing its potential as a target for therapeutic strategies.
Further research is needed to consolidate these findings and translate them into clinical practices for improving fluency in stuttering patients.

Potential confounding factors such as trial sequence presentation and the sparse imaging paradigm which may have affected the hemodynamic response.

Additional studies focusing on functional connectivity in speech tasks could enhance the understanding of speech production in various conditions.

Individuals who stutter may have:
- Reduced activation in left hemisphere auditory areas.
- Overactivation in the right hemisphere areas typically not dominant for language processing.
Task-based connectivity studies indicate that stuttering arises not only from impairments in specific brain regions but also from disrupted communication between these regions.