The effects of divided attention on visual evoked magnetic fields during mental arithmetic tasks and a verbal fluency task

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  • Ikeda Takuro
    Department of Physical Therapy, Faculty of Health Sciences at Fukuoka, International University of Health and Welfare
  • Mizuno Kentaro
    Department of Rihabilitation, Fukuoka Shinmizumaki Hospital
  • Goto Kazuhiko
    Department of Clinical Engineering, Hakata Medical Technical College
  • Goto Yoshinobu
    Department of Occupational Therapy, Faculty of Health Sciences at Fukuoka, International University of Health and Welfare

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Other Title
  • 暗算と語想起による注意分散が視覚誘発脳磁界に及ぼす影響
  • アンザン ト ゴ ソウキ ニ ヨル チュウイ ブンサン ガ シカク ユウハツ ノウ ジカイ ニ オヨボス エイキョウ

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Abstract

<p>[Objective] The aim of this study was to investigate the specific spatiotemporal brain processes of divided attention in mental arithmetic and verbal fluency tasks using visual evoked magnetic fields (VEFs). <br>[Methods] VEFs were recorded using a 306-channel MEG in 14 healthy adult right-handed volunteers. To evoke visual responses, a hemifield black–white checkerboard pattern was phase-reversed at a rate of 1 Hz to stimulate either the right or left visual hemifield. The subjects were instructed to fixate on a red dot placed 0.2º of arc laterally from the stimulated hemifield. VEFs were recorded with or without endogenous tasks, which included mental arithmetic tasks (serial subtraction and multiplication facts) and a verbal fluency task. The amplitudes and latencies of VEF components (the N75m, P100m and N145m) were measured. Additionally, VEFs were analyzed using fast Fourier transformation (FFT), and the topographic distribution of gamma band activity was then plotted. <br>[Results] The amplitude change in N75m on the left hemifield stimulation was significantly decreased in all endogenous tasks compared to the control condition (normal task). The latency change of the P100m on the left hemifield stimulation was significantly longer in the multiplication facts task than in the control condition and the successive subtraction task. In addition, the distribution of high-gamma band activity in the left hemifield was contracted to the right frontal area during both types of dispersion tasks. Furthermore, the power value of the right occipital area was expanded in both the occipital lobe and parietal lobe during the multiplication facts task. <br>[Conclusions] Our results suggest that the VEF changes are the evidence of the inhibition of visual information processing in the primary visual cortex that occurs during endogenous tasks. In addition, the high gamma band activity changes maybe evidence of the neural connection or inhibition of information processing in cortico-cortical communication.</p>

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