Single, but not dual, attention facilitates statistical learning of two concurrent auditory sequences

Tatsuya Daikoku,Masato Yumoto

doi:10.1038/s41598-017-10476-x

Abstract

When we are exposed to a novel stimulus sequence, we can learn the sequence by extracting a statistical structure that is potentially embedded in the sequence. This mechanism is called statistical learning, and is considered a fundamental and domain-general process that is innate in humans. In the real-world environment, humans are inevitably exposed to auditory sequences that often overlap with one another, such as speech sound streams from multiple speakers or entangled melody lines generated by multiple instruments. The present study investigated how single and dual attention modulates brain activity, reflecting statistical learning when two auditory sequences were presented simultaneously. The results demonstrated that the effect of statistical learning had more pronounced neural activity when listeners paid attention to only one sequence and ignored the other, rather than paying attention to both sequences. Biased attention may thus be an essential strategy when learners are exposed to multiple information streams.

Highlights

The brain is a learning system that adapts to multiple stimuli in a living environment
By learning statistics of transitional probabilities embedded in tone sequences, learners can predict a tone that will follow certain preceding tones in the sequence
Based on the combinations of frequent and rare tones in the two simultaneous tone sequences, there were four types of dyads: a dyad that consisted of two frequent tones in both sequences, a dyad that consisted of two rare tones in both sequences, a dyad that consisted of a frequent tone in a sequence and a rare tone in the other sequence, and vice versa

Summary

Introduction

The brain is a learning system that adapts to multiple stimuli in a living environment. The type of the stimulus, the structural character of the stream, attention to the stimuli, and the instructions given to the listeners may modulate neural responses for statistical learning in the auditory cortex. It is necessary to verify how neural responses in the auditory cortex are modulated by attention, in relation to prediction during auditory statistical learning. A previous study behaviourally demonstrated that attentional and nonattentional learning operated independently and in parallel when learners were presented with two simultaneous streams of stimuli[20]. Few studies have neurophysiologically investigated nonattentional and attentional statistical learning when humans are simultaneously exposed to multiple auditory streams of statistically structured sequences. We used magnetoencephalography (MEG) to investigate how attentional and nonattentional learning were reflected in neurological responses in the auditory cortex when participants were presented with two simultaneous streams of tones

Methods

Results

Conclusion