Reproducibility and sensitivity of detecting brain activity by simultaneous electroencephalography and near-infrared spectroscopy.

The aims were (1) to determine the sensitivity and reproducibility to detect the hemodynamic responses and optical neuronal signals to brain stimulation by near-infrared spectroscopy (NIRS) and evoked potentials by electroencephalography (EEG) and (2) to test the effect of novel filters on the signal-to-noise ratio. This was achieved by simultaneous NIRS and EEG measurements in 15 healthy adults during visual stimulation. Each subject was measured three times on three different days. The sensitivity of NIRS to detect hemodynamic responses was 55.2 % with novel filtering and 40 % without. The reproducibility in single subjects was low. For the EEG, the sensitivity was 86.4 % and the reproducibility 57.1 %. An optical neuronal signal was not detected, although novel filtering considerably reduced noise.