Localization of Cortical Activity During Japanese Grammatical Processing by Near-infrared Red Spectroscopic Mapping.

Abstract

  Near-infrared red spectroscopy (NIRS) is a noninvasive method that uses changes in cerebral blood volume (CBV) to measure relative changes in tissue concentration of oxygenated, deoxygenated and total hemoglobin. We used this technique to determine the cortical activation area during Japanese grammatical processing. To assess the relative changes in total hemoglobin, local changes in near-infrared absorption were measured simultaneously from seven points in both hemispheres. Nine subjects were presented target stimuli, and were asked to decide whether the attendant particle was “ga” or “wo” in Japanese grammatical tasks (experimental conditions), and whether the relative position was “front” or “back” in positioning tasks (baseline and control conditions). To control subvocal rehearsal and conceptual driven processing, the same Kanji character was presented visually as a target in the experimental and control conditions. Total hemoglobin increased in Broca's area when subjects made judgments in Japanese grammatical tasks, compared to positioning tasks. These results suggested that the task of deciding particles in Japanese grammatical processing might be an effective and objective method to assess language disorders.