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Abstract
Organic solvents are known toxic effects like vertigo, behavioral obstacle, distracting, and peripheral neuropathy in neuron areas. However, there have been few studies how neurotoxic solvents-exposed workers are affected by the cognitive load of preceding working memory tasks. Therefore, we used fMRI as to measure the neural correlates of working memory impairment in occupational workers who had from chronic exposure to organic solvent. Twenty-nine solvent-exposed workers were included in this study. Each participant concluded the verbal N-back tasks (1- and 2-back) during the fMRI acquisition. Within-group analyses showed fronto-parietal networks were active in each condition. Direct comparisons between 1- and 2-back showed higher activation during the 2-back than 1-back. We found that increased activation of these regions at lower task demand is associated with increased cost of implementing.
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 | Fig. 1.N-back task paradigm and schematic of block design. In the 0-back condition, participants were asked to identify the target letter “ㅅ” that was presented at the beginning of each trial block. In the N-back (N is 1 or 2) condition, they had to permanently memorize the recently presented letters in order to press a button whent a letter matched one that had been presented N letters before the present letter. The entire functional scanning run took approximately 4 min 48 sec. |
 | Fig. 2.Brain activation maps contrasted from 1- or 2-back minus 0-back task for all organic solvent-exposed subjects. The N-back working memory tasks revealted that a network of frontal and parietal cortical areas was active in both two conditions. |
 | Fig. 3.Brain activation maps derived from direct comparison between 2-back task and 1-back task. During the 2-back task, the organic solvent-exposed subjects showed higher activation than performing the 1-back task in the frontal and parietal cortical areas. No region showed significantly higher activation in the performing the 1-back task compared to the 2-back task. |
 | Fig. 4.Correlation between BOLD signal change and 1-back task performance (reaction time) (R=0.370, p＜0.05). |
Table 1.
Demographic, clinical, and laboratory characteris tics of organic solvent-exposed subjects.
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