EEG correlates of audiovisual associations in motion perception
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The process of associative learning has been considered to be one of the promising research areas in neuroscience to understand human perception, sensory plasticity, and multisensory integration that affects the way of perceiving external environment. Evidence suggests that associative learning causes unexpected lowlevel sensory plasticity in brain. Yet, how this effect occurs in low-level visual motion areas remains unclear. In order to examine the effect of audiovisual associations on visual motion perception, we conducted an experiment in which subjects are exposed to pre association test, associative learning and post association test phases. Moreover, EEG was recorded simultaneously to investigate neural mechanisms behind this effect. In associative learning task, a particular sound (low-frequency or high-frequency) was accompanied with a specific direction of random dot motion (leftward or rightward), and participants were asked to attend both sound and direction. Pre- and post-association tasks in which auditory-only, visual-only, audiovisual trials were presented are identical. During these trials, participants were asked to decide the direction of moving dots with a keypress except in auditory-only trials. We hypothesized that there will be significant differences in responses between pre- and post-association phases in accord with associative pairings that were given in associative learning phase. T-test results validated our hypothesis with a significance level at 0.01 (p-value = 0.008). In terms of neural mechanisms behind this effect, we also hypothesized that this effect originates from feedback mechanisms. ERP results indicated that associative learning in uences early temporal processes (100-150 ms) to auditory only condition, and interaction effect occurs late in time after stimulus onset (around 500 ms). In this context, ERP results supports the hypothesis by revealing that modulation in early temporal areas transmits information to high level association areas that project information to low level visual areas, thus high latency is observed after stimulus onset.