A systems perspective on the effective connectivity of overt speech production.
The aim of this study was to provide a computational system model of effective connectivity in the human brain underlying overt speech production. Meta-analysis of neuroimaging studies and functional magnetic resonance imaging data acquired during a verbal fluency task revealed a core network consisting of Brodmann's area (BA) 44 in Broca's region, anterior insula, basal ganglia, cerebellum, premotor cortex (PMC, BA 6) and primary motor cortex (M1, areas 4a/4p). Dynamic causal modelling (DCM) indicated the highest evidence for a system architecture featuring the insula in a serial position between BA 44 and two parallel nodes (cerebellum/basal ganglia), from which information converges onto the PMC and finally M1. Parameter inference revealed that effective connectivity from the insular relay into the cerebellum/basal ganglia is primarily task driven (preparation) while the output into the cortical motor system strongly depends on the actual word production rate (execution). DCM hence allowed not only a quantitative characterization of the human speech production network, but also the distinction of a preparatory and an executive subsystem within it. The proposed model of physiological integration during speech production may now serve as a reference for investigations into the neurobiology of pathological states such as dysarthria and apraxia of speech.
Institute for Neuroscience and Biophysics-Medicine (INB 3), Research Centre Jülich GmbH, 52425 Jülich, Germany. s.eickhoff@fz-juelich.de
Simon B
SB
Eickhoff
Stefan
S
Heim
Karl
K
Zilles
Katrin
K
Amunts
D006801:Humans; D008279:Magnetic Resonance Imaging; D008954:Models, Biological; D013060:Speech; D049490:Systems Biology