The next time you're on the phone, ask yourself if you're—without thinking—turning your head toward the ear the phone is pressed against. This tendency reflects a scientific reality that's the subject of a recent publication in the journal Journal of Neuroscience : our brain allocates more resources to analyzing sounds coming from the direction we are facing. Our results seem to show that we pay more attention to the side of the turn we take while walking", interpreter for Science and Future neuroscientist Liyu Cao, co-author of the publication.
“ In reality, we don't know much about the sensory process related to movement.", notes Liyu Cao. For technological and practical reasons, most research on the subject has been conducted under static conditions. Movement can be a disruptive factor for auditory perception, for example we often stop to listen carefully when we are about to detect faint sounds", illustrates the researcher.
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More brain activation by hearing while walking
To test the influence of walking on sound perception, participants walk a figure-8 path, wear a mobile electroencephalography (EEG) headset on their heads, and have sounds streamed continuously into each ear. By applying a different frequency to the left and right ears, the researchers can assign the corresponding response detected by the EEG to the correct ear. A modulated sound with an amplitude of 39 hertz would elicit a brain response of 39 hertz“, explains Liyu Cao. “ This testing method allows us to read the instantaneous brain response to the environment“.
Clearly, walking increased the intensity of brain activation in response to hearing sounds compared to standing. In addition, the direction of walking increased the intensity of processing sounds coming from the corresponding ear. "For example, when turning right, auditory training (brain activation, editor's note) to the auditory input from the right had an increased response amplitude“, illustrates Liyu Cao. “ We already know from our everyday experience that there must be a shift in the distribution of visual-spatial attention during turns. When we turn right, we look to the right. But it was previously unknown whether this shift in attention was specific to the visual domain.. » This new work reveals that hearing works this way too.
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Unexpected noise is better processed by the brain when we are still
In contrast, the sudden introduction of noise produced a very different effect. When played to both ears, the noise did not affect the intensity of brain activity. But when played to only one ear, brain activation was suddenly reduced during walking, much more than when standing. Our interpretation is that during walking, people are more sensitive to sudden auditory stimuli coming from the periphery", interprets Liyu Cao. For the researcher, these discoveries undoubtedly reflect a delicate mechanism of optimization of the distribution of our attentional resources, limited by nature.
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