title: Altered Modulation of Silent Period in Tongue Motor Cortex of Persistent Developmental Stuttering in Relation to Stuttering Severity.
abstract: Motor balance in developmental stuttering (DS) was investigated with Transcranial Magnetic Stimulation (TMS), with the aim to define novel neural markers of persistent DS in adulthood. Eleven DS adult males were evaluated with TMS on tongue primary motor cortex, compared to 15 matched fluent speakers, in a "state" condition (i.e. stutterers vs. fluent speakers, no overt stuttering). Motor and silent period thresholds (SPT), recruitment curves, and silent period durations were acquired by recording tongue motor evoked potentials. Tongue silent period duration was increased in DS, especially in the left hemisphere (P<0.05; Hedge's g or Cohen's dunbiased = 1.054, i.e. large effect size), suggesting a "state" condition of higher intracortical inhibition in left motor cortex networks. Differences in motor thresholds (different excitatory/inhibitory ratios in DS) were evident, as well as significant differences in SPT. In fluent speakers, the left hemisphere may be marginally more excitable than the right one in motor thresholds at lower muscular activation, while active motor thresholds and SPT were higher in the left hemisphere of DS with respect to the right one, resulting also in a positive correlation with stuttering severity. Pre-TMS electromyography data gave overlapping evidence. Findings suggest the existence of a complex intracortical balance in DS tongue primary motor cortex, with a particular interplay between excitatory and inhibitory mechanisms, also in neural substrates related to silent periods. Findings are discussed with respect to functional and structural impairments in stuttering, and are also proposed as novel neural markers of a stuttering "state" in persistent DS, helping to define more focused treatments (e.g. neuro-modulation).
authors.affiliation: IRCCS Fondazione Ospedale San Camillo, Venice, Italy.
authors.forename: Pierpaolo
authors.initials: P
authors.lastname: Busan
authors.affiliation: B.R.A.I.N. Center for Neuroscience, Department of Life Sciences, University of Trieste, Trieste, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Del Ben
authors.affiliation: ABC Balbuzie, Turin, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Bernardini
authors.affiliation: Department of Developmental and Social Psychology, University of Padua, Padua, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Natarelli
authors.affiliation: B.R.A.I.N. Center for Neuroscience, Department of Life Sciences, University of Trieste, Trieste, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Bencich
authors.affiliation: Department of Medical, Surgical and Health Sciences, University of Trieste, Trieste, Italy.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Monti
authors.affiliation: Department of Medical, Surgical and Health Sciences, University of Trieste, Trieste, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Manganotti
authors.affiliation: B.R.A.I.N. Center for Neuroscience, Department of Life Sciences, University of Trieste, Trieste, Italy.
authors.forename: Piero Paolo
authors.initials: PP
authors.lastname: Battaglini
mesh_terms: D000328:Adult; D003071:Cognition; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000503:physiopathology*; D013342:Stuttering / Q000503:physiopathology*; D014059:Tongue / Q000503:physiopathology*; D050781:Transcranial Magnetic Stimulation