Right-shift for non-speech motor processing in adults who stutter.
BACKGROUND
In adults who do not stutter (AWNS), the control of hand movement timing is assumed to be lateralized to the left dorsolateral premotor cortex (PMd). In adults who stutter (AWS), the network of speech motor control is abnormally shifted to the right hemisphere. Motor impairments in AWS are not restricted to speech, but extend to non-speech orofacial and finger movements. We here investigated the lateralization of finger movement timing control in AWS.


METHODS
We explored PMd function in 14 right-handed AWS and 15 age matched AWNS. In separate sessions, they received subthreshold repetitive transcranial magnetic stimulation (rTMS) for 20 min at 1Hz over the left or right PMd, respectively. Pre- and post-stimulation participants were instructed to synchronize their index finger taps of either hand with an isochronous sequence of clicks presented binaurally via earphones. Synchronization accuracy was measured to quantify the effect of the PMd stimulation.


RESULTS
In AWNS inhibition of left PMd affected synchronization accuracy of the left hand. Conversely, in AWS TMS over the right PMd increased the asynchrony of the left hand.


CONCLUSIONS
The present data indicate an altered functional connectivity in AWS in which the right PMd seems to be important for the control of timed non-speech movements. Moreover, the laterality-shift suggests a compensatory role of the right PMd to successfully perform paced finger tapping.
Neef
Nicole E
NE
Department of Clinical Neurophysiology, Georg-August-University Goettingen, Robert-Koch-Strasse 40, Goettingen, Germany.
Jung
Kristina
K
Rothkegel
Holger
H
Pollok
Bettina
B
von Gudenberg
Alexander Wolff
AW
Paulus
Walter
W
Sommer
Martin
M
D000293:Adolescent; D000328:Adult; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006225:Hand / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D009068:Movement / Q000502:physiology*; D013060:Speech / Q000502:physiology; D013342:Stuttering / Q000503:physiopathology*; D050781:Transcranial Magnetic Stimulation