Shaping Motor Neural Functioning of Developmental Stuttering to Improve Fluency

The Treatment of Persistent Developmental Stuttering: Shaping of Motor Neural Functioning to Improve Fluency

Developmental stuttering (DS) is a motor/speech disorder, characterized by specific alterations in the functioning of brain circuits. Non-invasive brain stimulation may be useful to shape the altered functioning and connectivity of these systems. As a consequence, this project aims to expand the neurophysiological understanding of DS, evaluating effects of transcranial electrical stimulation (tES) on speech fluency and brain functioning of adults with persistent DS. This project will provide high-impact insights into the functioning of DS neural system, also proposing innovative and/or personalized rehabilitation.

Investigators will evaluate the effect of different tES protocols targeting motor associative regions (about 10 "consecutive" stimulation sessions, in different days; tES will be compared to sham stimulation), in association with "canonical" speech therapy. About 30 right-handed adults with idiopathic and persistent DS since childhood will be recruited (age 18-59 years; please see below for inlusion/exclusion criteria). Participants will be subdivided in three groups (in association to speech therapy): two groups will undergo transcranial random noise stimulation or transcranial direct current stimulation, while the third group will undergo sham (placebo) stimulation . Effects will be assessed by measuring stuttering severity (i.e. objective evaluation of stuttering), behavioral/cognitive scales (i.e. subjective evaluation of stuttering), as well as a series of neurophysiological indexes useful to evaluate brain functioning and connectivity (e.g. TMS[transcranial magnetic stimulation]-induced motor/evoked potentials and EEG brain activity). Evaluations will be realized before the start of the tES protocols, as well as at the end of the cycles. Follow-up evaluations (starting from about 6 weeks after completion of stimulation sessions) are also foreseen after the end of the treatments.

Developmental Stuttering, Neuromodulation, transcranial Electrical Stimulation, Speech Fluency, Motor Networks

Participants will be randomly assigned to "real" neuromodulation or to "sham" modulation (in addition to speech therapy)

Transcranial Random Noise Stimulation (1.5 mA, High Frequency) administered by using surface scalp electrodes (20 minutes, initial part of the session) in correspondence of associative motor regions, during speech therapy sessions (45 minutes).

Transcranial Direct Current Stimulation (1.5 mA, anodal) administered by using surface scalp electrodes (20 minutes, initial part of the session) in correspondence of associative motor regions, during speech therapy sessions (45 minutes).

Sham stimulation administered by using surface scalp electrodes (20 minutes, initial part of the session) in correspondence of associative motor regions, during speech therapy sessions (45 minutes).

transcranial Random Noise Stimulation, transcranial Direct Current Stimulation, or Sham are administered (by means of surface electrodes) on associative motor regions during speech therapy sessions (20 minutes, in the initial part of the sessions; 1.5 mA).

Speech Therapy is associated to transcranial electrical stimulation or sham, during stimulation sessions. Total duration of the single session: 45 minutes

Utilization of (objective) scales to evaluate stuttering severity and speech fluency (Stuttering Severity Instrument [range 0-56; higher values indicate higher numbers of dysfluencies])

Utilization of Transcranial Magnetic Stimulation to evaluate excitability (and reactivity) of motor cortex

Utilization of EEG to evaluate brain functioning and brain connectivity (delta, theta, alpha, beta, and gamma activity)

Utilization of (subjective) scales to evaluate stuttering severity/speech fluency (e.g. Premonitory Awareness in Stuttering Scale [range 0-42; higher values indicate higher "invasiveness" of stuttering with respect to quality of life])

Utilization of (subjective) scales to evaluate stuttering severity/speech fluency (e.g. Premonitory Awareness in Stuttering Scale [range 0-42; higher values indicate higher "invasiveness" of stuttering with respect to quality of life])

Utilization of (objective) scales to evaluate stuttering severity and speech fluency (Stuttering Severity Instrument [range 0-56; higher values indicate higher numbers of dysfluencies])

Utilization of Transcranial Magnetic Stimulation to evaluate excitability (and reactivity) of motor cortex

Utilization of EEG to evaluate brain functioning and brain connectivity (delta, theta, alpha, beta, and gamma activity)

Utilization of (subjective) scales to evaluate cognitive/behavioral reactions (e.g. Beck Depression Inventory [range 0-63; higher values indicate higher presence of depressive symptoms])

Utilization of (subjective) scales to evaluate cognitive/behavioral reactions (e.g. Beck Depression Inventory [range 0-63; higher values indicate higher presence of depressive symptoms])

(main) Inclusion Criteria: -Right-handed adults with idiopathic, persistent DS since childhood (main) Exclusion Criteria: Contraindications to non-invasive brain stimulation; Currently assumption of drugs acting on the Central Nervous System; Presence of overt neurological/psychiatric/medical conditions or overt comorbidities (e.g. obsessive-compulsive disorder).