The contribution of mesiofrontal cortex to the preparation and execution of repetitive syllable productions: an fMRI study.
Clinical data indicate that the brain network of speech motor control can be subdivided into at least three functional-neuroanatomical subsystems: (i) planning of movement sequences (premotor ventrolateral-frontal cortex and/or anterior insula), (ii) preparedness for/initiation of upcoming verbal utterances (supplementary motor area, SMA), and (iii) on-line innervation of vocal tract muscles, i.e., motor execution (corticobulbar system, basal ganglia, cerebellum). Using an event-related design, this functional magnetic resonance imaging (fMRI) study sought to further delineate the contribution of SMA to pre-articulatory processes of speech production (preceding the innervation of vocal tract muscles) during an acoustically paced syllable repetition task forewarned by a tone signal. Hemodynamic activation across the whole brain and the time courses of the responses in five regions of interest (ROIs) were computed. First, motor preparation was associated with a widespread bilateral activation pattern, encompassing brainstem structures, SMA, insula, premotor ventrolateral-frontal areas, primary sensorimotor cortex (SMC), basal ganglia, and the superior cerebellum. Second, calculation of the time courses of BOLD ("blood oxygenation level-dependent") signal changes revealed the warning stimulus to elicit synchronous onset of hemodynamic activation in these areas. However, during 4-s intervals of syllable repetitions SMA and cerebellum showed opposite temporal activation patterns in terms of a shorter (SMA) and longer (cerebellum) latency of the entire BOLD response-as compared to SMC, indicating different pacing mechanisms during the initial and the ongoing phase of the task. Nevertheless, the contribution of SMA was not exclusively restricted to the preparation/initiation of verbal responses since the extension of mesiofrontal activation varied with task duration.
Brendel
Bettina
B
Department of General Neurology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany. bettina.brendel@uni-tuebingen.de
Hertrich
Ingo
I
Erb
Michael
M
Lindner
Axel
A
Riecker
Axel
A
Grodd
Wolfgang
W
Ackermann
Hermann
H
D000328:Adult; D001921:Brain / Q000098:blood supply / Q000502:physiology; D001931:Brain Mapping; D002560:Cerebrovascular Circulation; D005260:Female; D005625:Frontal Lobe / Q000098:blood supply / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009434:Neural Pathways / Q000098:blood supply / Q000502:physiology; D010100:Oxygen / Q000097:blood; D010700:Phonetics; D011597:Psychomotor Performance / Q000502:physiology*; D013060:Speech / Q000502:physiology*; D013997:Time Factors; D055815:Young Adult
D010100:Oxygen