In accordance with our observations of N100, Ermolaev and Kleinman (1983) found an inverse relationship between background illumination and N130 amplitude. Moreover, consistent with our observations, Noguchi and Sakaguchi (1999) observed significant changes in alpha power with changes in color–temperature. In summary, our findings provide compelling evidence that the illumination condition substantially influences our attentional processing which was reflected in the significant modulations

of EEG activity. Further studies on illumination parameter-dependent efficacy of the cognitive performance and selection of the effective illumination parameters are necessary to develop appropriate applications to enhance the efficacy of

our work-performance. For instance, such an see more illumination-mediated application to inefficient Alectinib or impaired cognitive performance for probing its potential utility in the enhancement of work efficacy constitutes one of our future subjects of investigation. EEG was recorded from all 23 neurologically normal participants (11 females; mean age 23; age range 19–31 years) in this study in accordance with the ethics guidelines established by the Institutional Review Board of Yonsei University and the Declaration of Helsinki (World Medical Association, 1964; 2002). Participants provided informed consent prior to the start of the experiment. All had normal or corrected-to-normal vision. We used a 60×60 cm2 plate as the illumination source, which had 14×14 light-emitting diode (LED) arrays installed inside; this source was placed just above and behind many the participant with a tilt angle of 10° to the vertical line as shown in Fig. 3A. A controller (WE7000, Yokogawa, Japan) could regulate the illuminance and color–temperature of the LEDs. To make the illumination as homogenous as possible all around the participant, the present experiment was performed within a capsule-shaped light-reflecting structure (Fig. 3A) called the “Ganzfeld-dome,” with an optical geometry with a 2-m diameter. Four different illumination conditions were provided with

a factorial design of 2 color–temperatures (3000 K and 7100 K) by 2 illuminance levels (150lx and 700lx). This resulted in (1) the cool-dark (7100 K and 150lx), (2) the cool-light (7100 K and 700lx), (3) the warm-dark (3000 K and 150lx), and (4) the warm-light (3000 K and 700lx) conditions. Higher color–temperatures lead to bluish light, which we feel is a cool illumination condition; whereas lower color–temperatures produce yellowish or reddish light, which we feel is a warm illumination condition. These specific illumination parameters were chosen on the basis of the Kruithof curve (Kruithof, 1941), taking the technical limitation of the illumination device into consideration. Both comfortable and uncomfortable combinations of illuminance and color–temperature parameters have been described in the Kruithof curve.