Sung-Jin Bae

Altered working memory process in the manganese-exposed brain.

Chronic manganese (Mn) exposure often leads to impairments in fine motor and cognitive functions, particularly memory. However, the neural correlates of Mn-induced alterations in memory remain unclear. In the present study, we performed functional MRI (fMRI) with 2-back memory tests to assess the neural correlates of Mn-induced memory impairment in response to subclinical dysfunction in the working memory networks in welders exposed to Mn for extended periods of time. Within-group and between-group analyses revealed that brain activity in working memory networks was increased in welders with chronic Mn exposure during the 2-back verbal working memory task compared to healthy control individuals. Therefore, our fMRI findings indicate that welders might require more neural resources in working memory networks to compensate for subtle deficits in working memory and altered working memory processes, even if they performed the tasks at the same level as healthy control individuals.

Evaluation of white matter structures in patients with tinnitus using diffusion tensor imaging.

Recent functional imaging studies have demonstrated that the sensation of tinnitus is associated with activity in cortical regions functionally linked to subserve the generation, perception and processing of the tinnitus stimulus. Previous functional imaging studies have focused primarily on the cortical centers. However, none of these examined the functional nature of associated white matter interconnecting these cortical centers. In this study, we investigate the integrity of white matter tracts interconnecting the auditory system to the parietal and frontal corticies in tinnitus patients using diffusion tensor imaging. Our preliminary results suggest the possible involvement of associated white matter structures in addition to processing cortical centers in tinnitus patients compared with healthy subjects.