Abstract: PURPOSE: In our everyday life, we are constantly exposed to stimuli that elicit brief emotional reactions, such as sad news, threatening images, or melancholic music. Previous studies have found that changes in affective state produced by negative visual images can affect visual size perception. Here we investigated whether such emotion-cognition interaction was still observed when using negative music, and the causal role of dorsolateral prefrontal cortex (DLPFC) in this process.
METHODS: During each trial, participants firstly listened to 30-s negative or neutral music, and then performed an Ebbinghaus illusion task, during which a target circle surrounded by four large or small context circles and a comparison circle were simultaneously presented, and they were required to adjust the size of the comparison circle to match that of the target circle without time limit. To stimulate bilateral DLPFC, anodal electrode and cathodal electrode were positioned at F3 and F4 (i.e., left anode/right cathode), or vice versa (i.e., left cathode/right anode). A constant current of 1-mA intensity with a duration of 15 minutes was initiated 5 minutes before the measure of the illusion effect. The setup of sham stimulation was identical to that of real stimulation, with the exception that the stimulator was turned on for 60 seconds.
RESULTS: In comparison with neutral music, negative music significantly reduced the Ebbinghaus illusion effect. Further, for the sham stimulation, similar pattern of results was observed. However, for the left anode/right cathode stimulation, the difference of illusion effect between negative and neutral music conditions disappeared; for the left cathode/right anode stimulation, the opposite pattern of results was observed, i.e., negative music significantly increased the illusion effect relative to neutral music.
CONCLUSIONS: The results show that prior exposure to negative music can affect visual size perception, left anode/right cathode and left cathode/right anode stimulation of prefrontal cortex can eliminate and reverse the emotional effect of music, respectively. The findings suggest that visual perception can be shaped by negative emotion transmitted from auditory modality, in favor of the causal role and hemispheric asymmetry of prefrontal cortex in emotion-cognition interaction.

Key words: negative emotion, music, Ebbinghaus illusion, tDCS