The effects of background noise on brain activity using speech stimuli on healthy young adults

Everyday spoken language processing does not occur in a novel acoustic environment, but rather in the presence of the interfering background noise. In the present study, brain activation associated with speech perception (SP) processing in quiet (SPQ) and SP processing in 5-dB SNR noise (SPN) was examined in 15 healthy young adults using functional MRI. The behavioral performance shows no significant difference between SPN and SPQ, suggesting that background noise does not always impair spoken language comprehension in young healthy participants. The fMRI results indicate that both the superior temporal gyrus (STG) and middle temporal gyrus (MTG) were significantly activated during both the SPQ and SPN. This is attributed to the use of verbal stimuli in this study. Further activation for both SPQ and SPN was also found in other temporal areas and the cerebellum. However interestingly, specific comparisons between SPQ and SPN revealed significant increases in brain activation in the left STG, left MTG and bilateral cerebellum during SPN compared to SPQ. We suggest that the higher processing demands due to the presence of background noise are associated with compensatory strategies to allow the cognitive system to overcome noise-related interference, particularly implicating involvement of the left STG, left MTG and bilateral cerebellum. Findings are discussed in the context of corroborating evidence of such compensation.