Oscillatory dynamics of inflectional processing: teasing apart defaultness and productivity effects in Russian verbs

Previous EEG studies demonstrated ample evidence for a major influence of morphological regularity on inflectional processing. However, regularity effects may be attributed to different properties of inflectional classes: to type frequency, to productivity, or to defaultness (assumed only in some models). In many languages, these factors cannot be teased apart, but it is possible in Russian. Several previous behavioural and fMRI studies claimed that one of the five productive inflectional verb classes shows the properties of the default. Relying on these works, we conducted an EEG study on Russian that involved a verb form selection task. We analysed ERPs and time-frequency responses to verbs from three inflectional classes and to pseudoverbs matching their relevant properties. We observed distinct time-frequency effects of defaultness and productivity. Default class verbs elicited broadband power modulations in different regions, which can be associated with working memory activity during the preparation for verb form selection. Productive class verbs modulated theta and beta power during verb form selection. Additionally, distinct time-frequency and ERP responses to real vs. pseudoverbs were observed during the whole task. These results speak for the special status of the default inflectional class in the inflectional system.