Prog Med Phys.  2015 Jun;26(2):72-78. 10.14316/pmp.2015.26.2.72.

The Neural Alteration according to Cognitive Load on Working Memory by Organic-Solvent Exposures

Affiliations
  • 1Department of Medical & Biological Engineering, Kyungpook National University, Daegu, Korea. ychang@knu.ac.kr
  • 2Department of Occupational and Environmental Medicine, University of Ulsan College of Medicine, Ulsan, Korea.
  • 3School of Electronics Engineering, College of IT Engineering, Daegu, Korea.
  • 4Department of Molecular Medicine, Kyungpook National University College of Medicine, Daegu, Korea.

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.

Keyword

Organic-Solvent exposure; Neurotoxicity; fMRI; Working memory

MeSH Terms

Magnetic Resonance Imaging
Memory, Short-Term*
Neurons
Peripheral Nervous System Diseases
Solvents
Vertigo
Solvents

Figure

  • 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).


Reference

References

1. Bale AS, Barone S, Jr. , Scott CS, Cooper GS. A review of potential neurotoxic mechanisms among three chlorinated organic solvents. Toxicol Appl Pharmacol. 255:113–126. 2011.
Article
2. Spencer PS, Schaumburg HH, Sabri MI, Veronesi B. The enlarging view of hexacarbon neurotoxicity. Crit Rev Toxicol. 7:279–356. 1980.
Article
3. Firestone JA, Longstrength WTJ. Neurologic and psychiatric disorders. Rosenstock L, Cullen M, Brodkin C, Redlich C: Textbook of clinical occupational and environmental medicine. 4thed, Saunders Elsevier, Philadelphia (. 2004. ), pp.645–660.
4. Mikkelsen S. Epidemiological update on solvent neurotoxicity. Environ Res. 73:101–112. 1997.
Article
5. Baker EL. A review of recent research on health effects of human occupational exposure to organic solvents. A critical review. J Occup med. 36:1079–1092. 1994.
6. Haut MW, Leach S, Kuwabara H, et al. Verbal working memory and solvent exposure: a positron emission tomography study. Neuropsychology. 14:551–558. 2000.
Article
7. Owen AM, McMillan KM, Laird AR, Bullmore E. N-back working memory paradigm: a metaanalysis of normative functional neuroimaging studies. Hum Brain Mapp. 25:46–59. 2005.
Article
8. Evans A, Collins DL, Mills SR, et al. 3D statistical neuroanatomical models from 305 MRI volumes. Proc IEEE-Nuclear Science Symposium and Medical Imaging Conference. 3:1813–1817. 1993.
Article
9. Braver TS, Cohen JD, Nystrom LE, et al. A parametric study of prefrontal cortex involvement in human working memory. NeuroImage. 5:49–62. 1997.
Article
10. Cohen JD, Perlstein WM, Braver TS, et al. Temporal dynamics of brain activation during a working memory task. Nature. 386:604–608. 1997.
Article
11. Petrides M. Dissociable roles of mid-dorsolateral prefrontal and anterior inferotemporal cortex in visual working memory. Journal of Neuroscience. 20(19):7496–7503. 2000.
Article
12. Hagoort P, Hald L, Bastiaansen M, Petersson KM. Integration of word meaning and world knowledge in language comprehension. Science. 304(5669):438–441. 2004.
Article
13. Barbey AK, Kruger F, Grafman J. An evolutionarily adaptive neural architecture for social reasoning. Trends Neurosci. 32(12):603–610. 2009.
Article
14. Rypma B, Berger JS, D'Esposito M. The influence of working memory demand and subject performance on prefrontal cortical activity. J CognNeurosci. 14(5):721–731. 2002.
15. Davachi L, Maril A, Wagner AD. When keeping in mind supports later bringing to mind: neural markers of phonological rehearsal predict subsequent remembering. Journal of Cognitive Neuroscience. 13(8):1059–1070. 2001.
Article
16. Henson RN, Burgess N, Frith CD. Recoding, storage, rehearsal and grouping in verbal short-term memory: An fMRI study. Neuropsychologia. 38(4):426–440. 2000.
Article
17. Majerus S, Laureys S, Collette F, et al. Phonological short-term memory networks following recovery from Landau and Kleffner syndrome. Hum Brain Mapp. 19:133–144. 2003.
Article
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