Thalamus and Bilingualism: Evidence from fMRI

Document Type : Original Article

Authors

• Simin Meykadeh ¹
• Werner Sommer ²
• Seyed a,mir hossien Batouli ³

¹ PhD in Linguistics, Tarbiat Modares University, Tehran, Iran

² Professor in Psychology, Humboldt-Universität zu Berlin, Berlin, Germany

³ Assistant Professor, Department of Neuroscience and Addiction Studies, Tehran University of Medical Sciences, Tehran, Iran

https://doi.org/10.22067/jlkd.2023.83396.1179

Abstract

Bilingualism is associated with structural adaptations of subcortical regions taking part in controlling multiple languages. The thalamus is a paired gray matter structure located near the center of the brain, regulating the information transmission to cortical regions. In a recent fMRI study, the sensitivity of the thalamus to grammatical and ungrammatical stimuli has been shown at whole-brain level in the first language (L1) of bilinguals. This study explored the activation patterns of bilateral thalamus in both L1 and L2 using a ROI-based approach. To do so, 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 thalamus. Considering that L1 was the dominant language in this study and gave rise to larger reversed language dominance effects, it was suggested that the engagement of the thalamus in L1 is not associated with syntactic processing but instead may exert an overall monitoring and control function for language-specific cortical activities.

Keywords

• Thalamus
• Bilingualism
• L1
• Switching Costs
• Left Hemisphere
• fMRI

Main Subjects

• Neurology of the language

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