Диссертация (Experimental study of several core concepts of theoretical morphology (on the material of russian) - regularity, syncretism, markedness), страница 9

Previous neuroimagingstudies arguing for the DR approach, as well as a number of studiesthat do not directly address the DR vs. SR debate (e.g., MarslenWilson and Tyler, 2007; Bozic et al., 2010, 2013; Szlachta et al.,2012), argue that rule-based processing is supported by the frontoparietal network, particularly by Broca’s area. However, only twofMRI studies comparing regular vs. irregular form productionfound more activation in Broca’s area for regulars (Dhond et al.,2003; Oh et al., 2011). Increased left IFG activation for regularswas also observed in an fMRI study where the processing of spoken regular and irregular forms was compared in a same-differentjudgment task (Tyler et al., 2005).Other fMRI studies report the opposite pattern: Broca’s areawas activated more by irregulars (Beretta et al., 2003; de DiegoBalaguer et al., 2006; Desai et al., 2006; Sahin et al., 2006).

Twoalternative explanations are proposed. Proponents of the DRapproach suggest that these results can be explained by conflictmonitoring between the regular rule and irregular form or by inhibition of regular rule application (e.g., Sahin et al., 2006). Desaiet al.

(2006) argue for the SR approach: they conclude that theobserved activation differences reflect the greater processing loadposed by irregulars, which rely on less frequent inflection patterns than RVs and therefore have greater attentional and responseselection demands.In Slioussar et al. (2014), nonce verbs and nouns were addedto the comparison. Participants silently read stimuli and producedaloud particular forms from them. We found that functional activity within the fronto-parietal network was influenced by regularityand lexicality: it was greater for IVs than for regular ones and fornonce verbs than for real ones. We demonstrated that the effectsof regularity and lexicality were very similar and concluded thatthe observed BOLD changes were induced not by (ir)regularityas such, but by the increase of processing load from RV toirregular (IV) to regular nonce verb (RNV) to irregular nonceverbs (INV).This conclusion was supported by the (RV > B) < (IV > B) <(RNV > B) < (INV > B) parametric contrast, where B is animplicitly modeled baseline, and by behavioral results: the numberof mistakes increased from RV to IV to RNV to INV condition.

Theresults for nouns were similar. Only the main effect of regularitydid not reach significance in the factorial analysis of fMRI data –presumably, because the only irregular feature we could find forour noun stimuli was rather minor (see A Brief Description of theRussian Verb and Noun Systems).A PREVIOUS PPI STUDY OF INFLECTIONAL MORPHOLOGY AND THEPRESENT STUDYWe were only able to find only one PPI study of inflectionalmorphology (Stamatakis et al., 2005). In this study, functionalconnectivity between functionally predefined regions of interestFrontiers in Human Neuroscience(ROIs) located in the left inferior frontal gyrus (LIFG), anteriorcingulate cortex (ACC), superior temporal gyrus (STG), and middle temporal gyrus (MTG) was assessed during the same/differentjudgment task.

Stimuli were aurally presented pairs of Englishwords and nonce words, in particular, RV and IV pairs like jumped– jump and thought – think.Stamatakis et al. (2005) report a positive influence of LIFGactivity on the activity in the left STG/MTG and a modulatoryinfluence of ACC activity on this fronto-temporal connectivity. The former effect did not depend on regularity per se, butwe know from the subtractive analysis of the data reported inTyler et al. (2005) that RVs activated the LIFG, bilateral STG andMTG significantly more than irregular ones in this study. Thelatter effect was significantly stronger for regulars than for irregulars.

Stamatakis et al. (2005) believe that these findings indicategreater engagement of the fronto-temporal network in RV processing, with the ACC playing a monitoring role. They conclude:“this reflects the additional processing demands posed by regular inflected forms, requiring modulation of temporal lobe lexicalaccess processes by morphological parsing functions supported bythe LIFG” (p. 116).Undertaking a PPI analysis of our data, we were primarilyinterested in two things. Firstly, an advantage of this approachis that task-dependent connectivity changes may be detected evenwhen the levels of functional brain activity are not affected byexperimental manipulations.

We aimed to reveal functional interactions underlying changes in functional activity observed withinthe LIFG during regular and irregular form production (Slioussar et al., 2014). As we noted above, the increase in LIFG activityin IV trials was explained by the difference in processing loadbetween these two tasks in Slioussar et al. (2014). In principle,this difference could attenuate functional activity changes associated with regularity.

Therefore we turned to PPI analysis to findout whether this was indeed the case and to tease apart connectivity changes associated with morphological properties and withcognitive demands.Secondly, we were interested how our findings would compareto Stamatakis et al.’s (2005) given several important differences inour experiments. First of all, there are obvious differences in theexperimental task and in the language used (morphologically poorEnglish vs. morphologically rich Russian).

Furthermore, subtractive analyses presented in Tyler et al. (2005) and Slioussar et al.(2014) revealed the opposite results, in particular, the LIFG wasmore activated by regulars in the first study and by irregulars inthe second. Finally, the analyses of behavioral data (the number ofmistakes in different conditions) showed that irregular trials weremore difficult than regular ones for the participants of our study,while Tyler et al.

(2005) reported very similar accuracy rates.In general, we wanted to see whether the functional connectivity of LIFG would be substantially different during comprehensionand production of regular vs. irregular forms (although our taskdefinitely involves a silent reading stage as well). In particular,we expected that if the findings from Stamatakis et al. (2005)are genuine regularity effects, we might be able to replicate themdespite all the differences, teasing them apart from processing difficulty effects identified in Slioussar et al.

(2014). Foreshadowingthe results, this is exactly what we did in the present study.www.frontiersin.org29February 2015 | Volume 9 | Article 36 | 3Kireev et al.A PPI study of Russian verb productionMATERIALS AND METHODSPARTICIPANTSTwenty-one healthy subjects participated in the study (13 females,8 males). All participants were native speakers of Russian, 19–32 years of age, with no history of neurological or psychologicaldisorders. All participants were right-handed, as assessed by theEdinburgh Handedness Inventory (Oldfield, 1971).

Subjects weregiven no information about the specific purpose of the study. Allsubjects gave their written informed consent prior to the studyand were paid for their participation. All procedures were in accordance with the Declaration of Helsinki and were approved by theEthics Committee of the N.P. Bechtereva Institute of the HumanBrain, Russian Academy of Sciences.MATERIALSMaterials consisted of eight groups of real and nonce verbs andnouns, illustrated in Table 1 (a complete list is given in Supplementary Material). The first group of 35 real verbs belonged to the AJclass (RV); the second group contained 35 verbs from several smallnon-productive classes (IV).

Only unprefixed imperfective verbswere used. Two matching groups of 35 nonce verbs (RNVs andINVs) mimicked the general characteristics of the correspondingreal verb groups (length and phonological properties of the stem).The first group of 35 real nouns had no stem changes (regularnouns, RN), while in the second group the last vowel of the stemwas dropped in many forms including the nominative plural form(irregular nouns, IN): e.g., šofer ‘driver’ – šofery vs.

koster ‘fire’ –kostry. All nouns were masculine, belonged to the first declensionand had the nominative plural form ending in -y. Two groupsof 35 nonce nouns (regular nonce nouns, RNN, and irregularnonce nouns, INN) were created to match two real noun groups.Frequency was balanced for all real stimulus groups using The Frequency Dictionary of the Modern Russian Language (Lyashevskayaand Sharoff, 2009). Stimuli in all groups were matched for length(see Supplementary Material).Vowels are dropped only in a subgroup of noun stems endingin particular vowel and consonant clusters (e.g., -er, -or, -el, -oletc.).

We selected stems with such clusters both for irregular andfor RN groups so as not to make the former more phonologicallyhomogenous than the latter. Final vowel dropping is usually predictable from the combination of consonants before this voweland from the position of the stress. However, since stimuli werepresented visually, no information about stress was available fornonce nouns, and different nominative plural forms could be licitlyderived from them.LANGUAGE PROTOCOL AND EXPERIMENTAL fMRI PARADIGMIn total, we had 280 stimuli.

Each stimulus was visually presentedfor 700 ms. Fixation crosses (“xxxxx”) were displayed during interstimulus intervals, which varied between 3100 and 3500 ms witha 100 ms step. 140 “null-events” (fixation crosses) were pseudorandomly intermixed with the stimuli (Friston et al., 1999). Theexperiment was divided into three consecutive runs with 2–5 minrest between them and was preceded by a short practice run. Thefirst 10 dummy scans of each run were discarded. Stimulus deliveryand synchronization with fMRI data acquisition were carried outvia the Eloquence fMRI System (In vivo) and E-Prime software(version 1.1, Psychology Software Tools Inc., Pittsburgh, PA, USA).Verbs were presented in the infinitive form, and nouns were presented in the nominative singular form.