Impact of Characteristics of Noise Added to Auditory Stimulus on Auditory Steady-State Response

Auditory steady-state response (ASSR) is an EEG synchronized to periodic auditory stimulus such as amplitude modulated tone. Although ASSR can be applied to brain computer interface (BCI), namely, ASSR-BCI, to date the performance of ASSR-BCI has been much lower than advanced BCIs using other sensory modalities due to small amplitude and modulation of ASSR. It is thus crucial to increase the ASSR amplitude with the help of noise for developing an ASSR-BCI with high-performance which is comparable to other advanced BCIs. However, it has not been clarified what kind of noise characteristics are suitable for this aim. This study investigated noise intensity dependency of ASSR signal-to-noise ratio for six able-bodied subjects for three types of noise, namely, white, pink (1/$f$) and brown (1/$f^{2}$) noises with being added to an amplitude modulated tone. For all types of noise, the enhancement of ASSR amplitude was observed, indicating a stochastic resonance (SR) effect. The rate of cases manifesting SR was 59.6 % for the pink noise, 55.4 % for the white noise and 47.9% for the brown noise, respectively. It was found that the pink and white noises are preferable as an additive noise to the amplitude modulated tone to increase the ASSR amplitude effectively.