Bilateral Frontal Cortex Activation during Fragmented-Letter Identification is Greater than that during Complete-Letter Identification

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  • JIANG Yinlai
    Department of Intelligent Mechanical Systems Engineering, Kochi University of Technology
  • YANAGIDA Hirotaka
    Department of Informatics, Faculty of Engineering, Yamagata University
  • TAKAHASHI Tatsuhisa
    Department of Mathematical Information Science, Asahikawa Medical University
  • WANG Shuoyu
    Department of Intelligent Mechanical Systems Engineering, Kochi University of Technology

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To determine the organization of the neural system involved in the cognitive process for identifying fragmented letters through visual interpolation, we used near-infrared spectroscopy to examine whether the neural activation of distinct cerebral regions with different blood flows was evoked in 13 healthy young male subjects who were asked to identify complete and fragmented letters. Fragmented letters of the English alphabet (black, 72-point, MSP Gothic) were randomly displayed one by one on the screen of a personal computer in the same method as complete letters. Each of the letters was presented within a square (128 × 128 pixels) against a white background for 1200 ms. Fragmented letters were produced by randomly removing rectangular areas (6 × 12 pixels) that, overall, comprised 90% of the pixels from complete letters. The rectangles removed were randomly rotated. The rates of correct identification in reading letters were 61 ± 7% for fragmented letters and 100% for complete letters in all subjects, which were significantly different (P < 0.05). Concentrations of oxyhemoglobin in the dorsolateral frontal gyrus [at or near Brodmann area (BA) 9], the inferior and middle frontal gyrus (at or near BA 44 and BA 45), and the lateral premotor and primary motor gyrus (at or near BA 6 and BA 4) in the right and left hemispheres were significantly (P < 0.05) greater during fragmented-letter identification than during complete-letter identification. These results demonstrated that fragmented-letter identification was accompanied by greater activation in the bilateral dorsolateral, inferior, and lateral frontal cortices, compared to complete-letter identification. However, this study could not determine any specific locus of the neural substrate that processed the visual interpolation to compensate for the lack of segments in fragmented letters or the generation of mental-imagery letters.

収録刊行物

  • 生体医工学

    生体医工学 50 (2), 219-226, 2012

    公益社団法人 日本生体医工学会

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