Cortical and subcortical mechanisms in persistent stuttering ...

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Table 1-2 Results from diffusion tensor imaging yielded aberrant fractional anisotropy (FA) in persons who stutter. Most consistent is the observation of a reduced FA in the white matter of the left premotor region (italic font). Reference lower FA higher FA (Sommer et al., 2002a) left rolandic operculum (Watkins et al., 2008) (Chang et al., 2008) (Kell et al., 2009) (Cykowski et al., 2010) (Chang et al., 2010) 26 ▫pars orbitalis in the right inferior frontal gyrus ▫left and right posterior inferior frontal gyrus ▫left and right precentral gyrus (middle) ▫left and right ventral premotor cortex ▫right posterior supramarginal gyrus ▫left dorsal supramarginal gyrus ▫in the right and left cerebellar white matter ▫in white matter tracts such as the right corticospinal tract (at the level of the midbrain) ▫the medial lemniscus ▫right middle cerebellar peduncle ▫the corticospinal/corticobulbar tract bilaterally ▫the left arcuate fasciculus in the left rolandic operculum region ▫a posterior-lateral region underlying the supramarginal gyrus ▫more anterior than rolandic operculum ▫left arcuate fasciculus ▫a continuous region from the left forceps minor near its junction with the left anterior corona radiata, extending dorsally and caudally through the third division of the left superior longitudinal fasciculus (including and WM deep to Brodmann area BA 44) ▫within the body of the corpus callosum ▫left posterior inferior frontal gyrus (ventral to the area of decrease described above) ▫right postcentral gyrus ▫right supramarginal gyrus ▫left anterior insula/inferior frontal region ▫the left orbitofrontal cortex ▫underneath the left intraparietal sulcus right rolandic operculum
Chapter 1 Scope of the dissertation 1.6 Scope of the dissertation The objective of this dissertation is to explore cortical and subcortical mechanisms in stuttering. In the first study, repetitive transcranial magnetic stimulation (rTMS) helped discovering a dysfunction of the left dorsolateral premotor cortex in control of paced finger movements and a compensatory role of its right hemispheric homologue in stuttering. While previous neuroimaging studies elucidated altered activation patterns, we were able to directly show for the first time that the right hemisphere might indeed play a compensatory rather than maladaptive role for non-speech functions in persistent developmental stuttering. In the second study, we aimed at detecting neurophysiological changes in the primary motor tongue representation of the left and right hemisphere in adults with persistent stuttering. Overcoming methodological challenges of transcranial magnetic stimulation at orofacial structures, this is the first study demonstrating an abnormality in intracortical excitability in persistent stuttering. The third study operationalized a behavioral approach to elucidate a possible disconnection between parieto-temporal regions involved in the phonological bottom up processing of speech stimuli and frontal regions mainly involved in the planning, programming and execution of speech movements. Behavioral deviations on a subclinical level might indicate a disturbed functional connectivity of these main networks of speech processing. The following studies aim particularly: (1) to test the lateralization of cortical control of paced finger movement timing in stuttering (2) to detect neurophysiological changes in the intracortical excitability in the primary motor tongue representation of the left and right hemisphere by employing single-pulse and paired-pulse TMS in adults who stutter and matched control subjects (3) to test the stability of phoneme percepts in stuttering by analyzing participants’ sensitivity to identify voiced and voiceless stop-consonants near the phoneme boundary. 27
Page 1 and 2: Cortical and subcortical mechanisms
Page 3: Statement of Originality I hereby d
Page 6 and 7: Appendix B - Stuttering and acquire
Page 8 and 9: PM premotor cortex PMd dorsolateral
Page 10 and 11: addition I conducted an fMRI study
Page 12 and 13: movements which enable a fast detec
Page 14 and 15: aforementioned description of the s
Page 16 and 17: encoding lexical, grammatical, phon
Page 18 and 19: 1.5.1 The cerebral dominance hypoth
Page 20 and 21: motor hand area in adults who stutt
Page 22 and 23: Figure 1-1 from Mink, 1996: Schemat
Page 24 and 25: dystonia (Berardelli et al., 2008).
Page 29: Chapter 2 Original articles 2 Origi
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Page 59: Chapter 2 Study 1 Non-speech motor
Page 63 and 64: Chapter 2 Study 2 Excitability of t
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Chapter 2 Study 2 Excitability of t
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Chapter 2 Study 3 Phoneme Categoriz
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Chapter 4 Conclusions and future pr
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include the conceptualizer, the for
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ω σ´ σ σ st� t� r�� Fi
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Figure A-5 Directions into velociti
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associated with dysarthria, aphasia
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Table B-2 Tuning of fluency by Deep
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A Appendix C Appendix C - Psycholin
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are useful tools to investigate int
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Benabid AL, Pollak P, Louveau A, He
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De Nil LF, Kroll RM, and Houle S. F
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Hickok G and Poeppel D. The cortica
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Levelt WJM. Speaking: from intentio
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Neef N, Paulus W, and Sommer M. Dem
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Smith A and Kelly E. Stuttering: A
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160 unilateral left subthalamic bra
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I thank Tibor Auer for his constant
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