Our newly developed 64-channel time-resolved optical tomographic imaging sy
stem using near-infrared light enables us to obtain a quantitative image of
hemoglobin concentration changes associated with neuronal activation in th
e human brain [H. Eda, I. Oda, Y. Ito, Y. Wada, Y. Oikawa, Y. Tsunazawa, M.
Takada, Y. Tsuchiya, Y. Yamashita, M. Oda, A. Sassaroll, Y. Yamada, M. Tam
ura, Multi-channel time-resolved optical tomographic imaging system, Rev. S
ci, Instrum., 70 (1999) 3595-3602]. Here, we used this optical imaging syst
em to demonstrate that the backward digit span (DB) task activated the dors
olateral prefrontal cortex (DLPFC) of each hemisphere more than the forward
digit span (DF) task in healthy adult volunteers, and higher performance o
f the DB task was closely related to the activation of the right DLPFC. The
se results suggest that visuospatial imagery is a useful strategy for the D
B task. Optical tomography described here is a new modality of neuropsychol
ogical studies. (C) 2000 Elsevier Science B.V. All rights reserved.