Test-retest reliability of MEG functional brain connectivity related to language production : Behavioral, functional, and structural underpinnings of reliable connectivity

The number of studies examining functional connectivity of the human brain is increasing rapidly. In this magnetoencephalography (MEG) study, we examined the reliability of connectivity related to language production in a picture naming test-retest paradigm, using data collected from the same participants on 2 separate days. We determined the connections that were reliable (Intraclass Correlation Coefficient, ICC) across both days and also examined the behavioral, functional, and structural properties underlying this reliability. A particularly salient finding among a rich set of results was a reliable pattern of beta connectivity increase in the left motor and frontal regions (0–400 ms and 400–800 ms after picture onset) and gamma connectivity decrease in the bilateral motor regions (800–1200 ms) which we suggest to represent the motor preparation of speech production. Furthermore, the reliable connections tended to be more frequently associated with language performance than the non-reliable ones. Finally, the reliable connections were also linked to stronger functional connectivity, as well as to stronger structural connectivity and shorter structural path length, as determined through diffusion MRI (magnetic resonance imaging). Overall, this study defines reliable language production-related functional connectivity and introduces practices that may increase reliability.