Neuronal Activity of Left Hemispheric Caudate Nucleus During Language-Switching: fMRI Evidence from Turkish-Persian Bilinguals

Document Type : Research Paper

Authors

1 PhD in Linguistics, Department of Linguistics, Faculty of Humanities, Tarbiat Modares University, Tehran, Iran.

2 Professor, Department of Psychology, Humboldt University of Berlin, Berlin, Germany.

3 Assistant Professor, Department of Neuroscience, Tehran University of Medical Sciences, Tehran, Iran.

Abstract

During switching from the dominant language into the non-dominant language, cognitive-related areas (i.e. caudate nucleus) are engaged in comprehending intra-sentential switches. The caudate nucleus is a component of the basal ganglia in the human brain which seems to be most implicated in the control of language (selection/inhibition). In a recent fMRI study, present authors detected the activation of the caudate nucleus specifically by the first language (L1) stimuli of bilinguals during a bilingual task at whole-brain level. Here, we explore the activation patterns of bilateral caudate nucleus in both L1 and L2 using a ROI-based approach. Therefore, the percentage of signal change for grammatical and ungrammatical stimuli in L1 and L2 was extracted as the intensity measure per participant. Thirty-six Turkish-Persian bilinguals (21 women) who had acquired their L2 at the age of 7 were selected. Based on the Bilingual Dominance Scale, there was no significant difference between the proficiency level of participants in L1 (Turkish) and L2 (Persian). Participants carried out an auditory grammaticality judgment task in an alternating language switching paradigm while fMRI images were acquired. ROI-based results confirmed the grammaticality effect only in L1 and the left caudate nucleus. We suggest that co-activation is modulated by linguistic constraints such as predictability and sentence context of the task, and that the caudate nucleus mainly contributed in language selection.

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History

  • Receive Date: 24 July 2023
  • Revise Date: 16 August 2023
  • Accept Date: 17 August 2023

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