A B S T R A C TResearch suggests that white noise may facilitate auditory working memory performance via stochastic resonance. Stochastic resonance is quantified by plotting cognitive performance as a function of noise intensity. The plot would appear as an inverted U-curve, that is, a moderate noise is beneficial for performance whereas too low and too much noise attenuates performance. However, knowledge about the optimal signal-to-noise ratio (SNR) needed for stochastic resonance to occur in the brain, particularly in the neural network of auditory working memory, is limited and demand further investigation. In the present study, we extended previous works on the impact of white noise on auditory working memory performance by including multiple background noise levels to map out the inverted U-curve for the stochastic resonance. Using functional magnetic resonance imaging (fMRI), twenty healthy young adults performed a word-based backward recall span task under four signal-to-noise ratio conditions: 15, 10, 5, and 0-dB SNR. Group results show significant behavioral improvement and increased activation in frontal cortices, primary auditory cortices, and anterior cingulate cortex in all noise conditions, except at 0-dB SNR, which decreases activation and performance. When plotted as a function of signal-to-noise ratio, behavioral and fMRI data exhibited a noise-benefit inverted U-shaped curve. Additionally, a significant positive correlation was found between the activity of the right superior frontal gyrus (SFG) and performance in 5-dB SNR. The predicted phenomenon of SR on auditory working memory performance is confirmed. Findings from this study suggest that the optimal signal-to-noise ratio to enhance auditory working memory performance is within 10 to 5-dB SNR and that the right SFG may be a strategic structure involved in enhancement of auditory working memory performance.

The present study examined the relationship between effective connectivity among frontotemporal brain regions and auditory working memory (AWM) performance. Twenty healthy participants performed a word-based backward recall task in four signal-to-noise ratio (SNR) conditions during functional magnetic resonance imaging scans. Functional data were pre-processed and analyzed using Statistical Parametric Mapping. Optimum connectivity model and strength of effective connectivity were analyzed using Dynamic Causal Modelling. Group results indicated significant brain activation in left superior temporal gyrus (STG) and left inferior frontal gyrus (IFG). Behavioral results showed that performance was enhanced in good SNR but worsened in low SNR. Bayesian model selection showed strong evidence of a bidirectional connection between left STG and left IFG. Correlation analyses showed a moderate positive linear relationship between effective connectivity from left STG to left IFG and behavioral performance. These findings suggest that the strength of effective connectivity from left STG and left IFG may underpin successful AWM performance.