Untersuchung der sprechbezogenen Veränderungen der Erregbarkeit im primären Motorkortex bei Stotternden und Kontrollprobanden mittels transkranieller Magnetstimulation
von Anna Sophia Elfers
Datum der mündl. Prüfung:2025-02-10
Erschienen:2025-01-14
Betreuer:Prof. Dr. Martin Sommer
Gutachter:Prof. Dr. Martin Sommer
Gutachter:PD Dr. Nicole E. Neef
Zum Verlinken/Zitieren:
http://dx.doi.org/10.53846/goediss-11008
Dateien
Name:Dissertation FINAL _05.01.25 - Version eDiss.pdf
Size:2.13Mb
Format:PDF
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Zusammenfassung
Englisch
Transcranial magnetic stimulation reveals a lack of reduction of intracortical inhibition of the tongue primary motor cortex in adults who stutter as compared to fluent speakers: Original neurogenic non-syndromic stuttering is a complex, multifactorial disease of the nervous system. It is characterized by involuntary speech dysfluencies, namely repetitions and prolongations of sounds and syllables as well as blockages. All these substantially complicate fluent speaking. Despite the high lifetime incidence of up to 8%, there are comparatively few studies which target the pathomechanisms of this disease. One mechanism relates to the modulation of orofacial cortical excitability, elucidated with transcranial magnetic stimulation (TMS) shortly before speech onset. In previous studies, fluent speakers demonstrated a time-dependent increase of excitability, which was lacking in adults who stutter (AWS). It is plausible to infer a disruption in of speech-related movement planning and articulation. Such an excitability increase (indicated by higher amplitudes of motor-evoked potentials, MEP) can be based on two distinct forms of intra-cortical modulation, namely reduced inhibition or increased facilitation. To probe the current state of excitatory and inhibitory interneurons wihthin the primary motor cortex, we used established conditioning – test paired-TMS measures, namely short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) at typical interstimulus intervals. We investigated speech-related changes in cortical excitability in 15 adults who stutter and 14 fluently speaking control subjects in the context of a speaking task and focused in particular on the phase of preparation for a speech act. We were able to show that the contralateral MEP amplitudes in the control group did increase immediately before the start of speech, in contrast to adults who stutter. The documented increase in MEP amplitude during speech preparation in fluent speakers could be attributed to a reduced intracortical inhibition (reduced SICI). In AWS, however, there was neither a decrease in SICI nor an increase in ICF. The results of our study show that a modulation of excitability within the primary motor tongue representation during speech preparation is missing in adults who stutter. We postulate that the lack of increase in excitability in the preparatory phase immediately before the start of speaking which was found in adults who stutter represents an abnormal initiation of movement programs, and that it can thus be associated with some typical speech disfluencies. Previous studies already linked SICI findings to a dysfunctional cortico-striato-thalamo-cortical loop. Our finding further strenghten and substantiate this link. In summary, our study supports the increasingly recognized theory of dysfunction in the complex processes of preparation, control and execution of speech movements in adults who stutter.
Keywords: stuttering; transcranial magnetic stimulation; speech; excitabilty of motor cortex; SICI
Schlagwörter: Transkranielle Magnetstimulation; Stottern; Sprechen; kortikale Erregbarkeit; SICI
