Multi-channel near-infrared spectroscopy detects specific inferior-frontal activation during incongruent Stroop trials

Near-infrared spectroscopy (NIRS) is an optical method, which allows non-invasive in vivo measurements of changes in the concentration of oxygenated (O2Hb) and deoxygenated (HHb) hemoglobin in brain tissue. In the present study we investigated 10 healthy subjects by means of multi-channel NIRS (Optical Topography; ETG-100, Hitachi Medical Co., Japan) during performance of congruent and incongruent trials of the Stroop color word task. With a similar pattern of activation for both congruent and incongruent Stroop trials in the NIRS channels located left superior-frontally, the results for O2Hb and the total amount of hemoglobin (Hb-tot) indicate specific activation for interference trials in inferior-frontal areas of the left hemisphere. This result is in line with several neuroimaging studies (fMRI, PET) that have already investigated the frontal activation related to Stroop interference, which further supports the assumption that multi-channel NIRS is sensitive enough to detect spatially specific activation during the performance of cognitive tasks.