Second language naming predicts left temporal pole integrity in aging bilinguals

Abstract

There is numerous of evidence showing the left temporal pole (TP) is involved specifically in object naming. It is believed which functions as a semantic hub (Lambon Ralph & Patterson, 2008) and is involved in lexical retrieval (Tranel, 2009). Interestingly, both naming ability and TP grey matter values deteriorate with age. In this study, we investigated the effect of increased proficiency in the first language (L1) and second language (L2) on TP structural values in healthy bilingual seniors. Thirty-six healthy bilinguals (55 to 78 age-old) were selected within the multilingual population in Hong Kong. They underwent structural MRI and the grey matter density (GMD) were analysed using Voxel-based Morphometry approach. Their bilingual demographic characteristics were examined and regressed with the structural values. The results indicated an age effect on the left TP, and a negative correlation between local GM values and the overall naming performance. Surprisingly, this correlation was significant only for naming in L2 but not L1. These suggest that there is a universal structural decline in the left TP for both monolingual and bilingual speakers. And, with better L2 naming, the left TP may be better tuned. This may induces structural benefits and protection effect against healthy aging.