Combined effects of mental load and background noise on CNS activity indicated by brain DC potentials

Abstract To assess combined effects of noise and mental load on brain activity, DC potential shifts were evaluated. In a 4-way repeated analysis of variance (ANOVA) design with Type of Noise, Sound Intensity, Mental Load, DC Recording Location as factor, 2-min epochs of noise exposure were compared in 18 subjects. Significant main effects were found for Type of Noise (white noise and street noise showing greater positive shifts than music sound), Mental Load (more positive shifts for mental load vs. no mental load), and DC Recording Location. Statistically significantly higher order interaction effects were also found. Low intensity of music sound diminished the mental load CNS activity (DC shifts), interpreted as a possible compensatory effect of soft music on mental load. The effect of mental load under street noise and white noise conditions depends on the CNS activity (DC shifts) caused by these background noises alone, showing a ceiling effect. Results indicate that CNS activity (DC shifts) apparent during mental load are changed by acoustic stimulation additionally applied and that this effect is dependent on type of noise/sound and sound intensity.