[PS-2.1] A DCM analysis of interactions within the fronto-temporal brain network associated with regular vs. irregular verb production

Kireev, M. 1, 2 , Slioussar, N. 3, 2 , Korotkov, A. 1 , Chernigovskaya, T. . 2, 1 & Medvedev, S. 1

1 N.P. Bechtereva Institute of the Human Brain, Russian Academy of Sciences, St. Petersburg, Russia
2 St. Petersburg State University, St. Petersburg, Russia
3 School of Linguistics, Higher School of Economics, Moscow, Russia

The debate between dual-route and single-route approaches (with/without a distinction between rule-based vs. memory-based processes, regular vs. irregular forms) has been central for the neuroimaging studies of inflectional morphology. But functional connectivity between brain areas involved remains largely unexplored. In a previous study, we reported an fMRI experiment in which participants generated forms from regular and irregular Russian verbs. The PPI analysis demonstrated that regular verb production is associated with increased connectivity between the lIFG and both left and right STG, compared to irregular verb production. In general, this supports dual-route models, but they argue the regularity effect to be left-latelarized.
In this study, ER-fMRI data from 18 subjects were submitted to the dynamic causal modeling analysis implemented in SPM12. Four models were created to test whether temporal cortex influences lIFG activity or vice versa; whether there is any lateralization difference between regular and irregular verbs. According to the Bayesian model selection, the optimal model assumes that regular verb production modulates the influence of the lSTG on the lIFG and irregular verb production is associated with modulation of bilateral STG influence on the lIFG. The results support the dual-route approach and indicate that rule-based processes differentially involve left-latelarized fronto-temporal network.