Hemodynamics of the left cerebral hemisphere during silent reading:analysis using near-infrared spectroscopy

The purpose of this study was to investigate the hemodynamic activity in the left cerebral hemisphere during silent reading in college students with typical development using near-infrared spectroscopy (NIRS). Sixty college students with typical development participated in this study. In the silent reading task, participants were asked to read a text from Andersen's fairy tale. Then, the change in oxygenated hemoglobin (oxy-Hb) concentration during silent reading of the text was calculated. The number of letters read during the silent reading task was also measured to calculate the silent reading speed. The average trend graph of 60 college students revealed increased oxy-Hb concentration in both the left inferior frontal gyrus (Broca's area) and the left inferior occipitotemporal gyrus during silent reading. A negative correlation was found between the change in oxy-Hb concentration in Broca's area and silent reading speed. A positive correlation was found between oxy-Hb concentration change in the left inferior occipitotemporal gyrus and silent reading speed. The increase in oxy-Hb concentration in Broca's area observed during silent reading may reflect effortful reading in students with reading difficulty. The increase in oxy-Hb concentration in the left inferior occipitotemporal gyrus observed during silent reading may reflect proficiency in reading. Our findings suggest the usefulness of NIRS in assessing reading function and its potential use in the diagnosis of developmental dyslexia. J. Med. Invest. 71 : 267-272, August, 2024.