title: State-dependent differences between functional and effective connectivity of the human cortical motor system.
abstract: Neural processing is based on interactions between functionally specialized areas that can be described in terms of functional or effective connectivity. Functional connectivity is often assessed by task-free, resting-state functional magnetic resonance imaging (fMRI), whereas effective connectivity is usually estimated from task-based fMRI time-series. To investigate whether different connectivity approaches assess similar network topologies in the same subjects, we scanned 36 right-handed volunteers with resting-state fMRI followed by active-state fMRI involving a hand movement task. Time-series information was extracted from identical locations defined from individual activation maxima derived from the motor task. Dynamic causal modeling (DCM) was applied to the motor task time-series to estimate endogenous and context-dependent effective connectivity. In addition, functional connectivity was computed for both the rest and the motor task condition by means of inter-regional time-series correlations. At the group-level, we found strong interactions between the motor areas of interest in all three connectivity analyses. However, although the sample size warranted 90% power to detect correlations of medium effect size, resting-state functional connectivity was only weakly correlated with both task-based functional and task-based effective connectivity estimates for corresponding region-pairs. By contrast, task-based functional connectivity showed strong positive correlations with DCM effective connectivity parameters. In conclusion, resting-state and task-based connectivity reflect different components of functional integration that particularly depend on the functional state in which the subject is being scanned. Therefore, resting-state fMRI and DCM should be used as complementary measures when assessing functional brain networks.
authors.affiliation: Max Planck Institute for Neurological Research, Neuromodulation & Neurorehabilitation, Cologne, Germany. Anne.Rehme@nf.mpg.de
authors.forename: Anne K
authors.initials: AK
authors.lastname: Rehme
authors.forename: Simon B
authors.initials: SB
authors.lastname: Eickhoff
authors.forename: Christian
authors.initials: C
authors.lastname: Grefkes
mesh_terms: D000328:Adult; D063132:Connectome / Q000379:methods*; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D009044:Motor Cortex / Q000033:anatomy & histology* / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D009415:Nerve Net / Q000033:anatomy & histology* / Q000502:physiology*