FMRI evidence for the involvement of the procedural memory system in morphological processing of a second language.

Christos Pliatsikas,Theodoros Marinis,Tom Johnstone

doi:10.1371/journal.pone.0097298

Abstract

Behavioural evidence suggests that English regular past tense forms are automatically decomposed into their stem and affix (played = play+ed) based on an implicit linguistic rule, which does not apply to the idiosyncratically formed irregular forms (kept). Additionally, regular, but not irregular inflections, are thought to be processed through the procedural memory system (left inferior frontal gyrus, basal ganglia, cerebellum). It has been suggested that this distinction does not to apply to second language (L2) learners of English; however, this has not been tested at the brain level. This fMRI study used a masked-priming task with regular and irregular prime-target pairs (played-play/kept-keep) to investigate morphological processing in native and highly proficient late L2 English speakers. No between-groups differences were revealed. Compared to irregular pairs, regular pairs activated the pars opercularis, bilateral caudate nucleus and the right cerebellum, which are part of the procedural memory network and have been connected with the processing of morphologically complex forms. Our study is the first to provide evidence for native-like involvement of the procedural memory system in processing of regular past tense by late L2 learners of English.

Highlights

According to dual systems of morphological processing, English past tense verbs are processed according to their regularity by native speakers [1]
Two participants from the NS group and one from the L2 group were excluded from the fMRI analysis due to excessive head movement, defined as any displacement above 3 mm from the position of the reference image
This study implemented a masked-priming task into an fMRI experiment in order to identify the neural correlates of morphological processing, and to investigate any differences between native and highly proficient late non-native speakers in the processing of English past tense inflection

Summary

Introduction

According to dual systems of morphological processing, English past tense verbs are processed according to their regularity by native speakers [1]. Vannest and colleagues presented English inflections and derivations, along with non-decomposable forms, and reported activations for complex vs simple words, in the LIFG and in the bilateral caudate nucleus This basal ganglia involvement in morphological processing has been reported in research with Italian speakers [11]. This suggests a dynamic restructuring of the cerebellum in L2 learners in order to acquire and/or accommodate the L2 morphological rule This fMRI study aims to investigate whether the proposed distinction between processing regular and irregular verbs [1] has its equivalents in brain activity of native and late non-native speakers of English. A similar prediction was drawn for the late L2 learners, based on the results from [15]: if the dual-route system is available to the late L2 learners, they are expected to engage a similar brain network for the processing of regular vs. irregular verbs

Ethics statement This research was approved by the University of Reading

Results

Discussion