Association between glutamate/glutamine and blood oxygen level dependent signal in the left dorsolateral prefrontal region during verbal working memory

Functional MRI (fMRI) has provided much insight into the changes in the neuronal activity on the basis of blood oxygen level dependent (BOLD) phenomenon. The dynamic changes in the metabolites can be detected using functional proton magnetic resonance spectroscopy (1H-fMRS). The strategy of combining fMRI and 1H-fMRS would facilitate the understanding of the neurochemical interpretation of the BOLD signal. The dorsolateral prefrontal region is critically involved in the processing of working memory (WM), as demonstrated by the studies involving the neuroimaging, neuropsychological, and electrophysiological experiments. In this study, we tested the association between BOLD signal and changes in brain metabolites in the left dorsolateral prefrontal region using N-back verbal WM task. We used single-voxel task-based 1H-MRS acquired in the left dorsolateral prefrontal region and fMRI during the performance of N-back verbal WM task to investigate the association between changes in metabolites and BOLD response in 10 healthy participants. The correlation between changes in metabolites and percent signal change was examined by the Pearson correlation. The Pearson correlation analysis revealed a significant positive correlation between the BOLD signal and glutamate/glutamine in the left dorsolateral prefrontal region during the verbal WM. Our finding suggests that glutamate/glutamine cycle plays a critical role in the neuronal activation as reflected by the changes in the BOLD response. Correspondence to Anupa A. Vijayakumari, PhD, Medical Image Processing Laboratory, Department of Imaging Sciences and Interventional Radiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, 695011 Kerala, India Tel: +91 471 252 4220; fax: +91 471 244 6433; e-mail: av.anupa@gmail.com Received February 2, 2018 Accepted February 7, 2018 © 2018 Wolters Kluwer Health | Lippincott Williams & Wilkins

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