Source:Cortex
Author(s): Christopher J. Fassnidge, Elliot D. Freeman
Some people hear what they see: car indicator lights, flashing neon shop signs, and people's movements as they walk may all trigger an auditory sensation, which we call the visual-evoked auditory response (vEAR or 'visual ear'). We have conducted the first large-scale online survey (N>4000) of this little-known phenomenon. We analysed the prevalence of vEAR, what induces it, and what other traits are associated with it.We asked respondents if they had previously experienced vEAR. Participants then rated silent videos for vividness of evoked auditory sensations, and answered additional questions.Prevalence appeared higher relative to other typical synaesthesias. Prior awareness and video ratings were associated with greater frequency of other synaesthesias, including flashes evoked by sounds, and musical imagery. Higher-rated videos often depicted meaningful events that predicted sounds (e.g. collisions). However, ratings were also driven by the low-level 'motion energy' of non-predictive flashing or moving patterns, specifically in respondents who had previous awareness of vEAR.Our motion energy analysis suggests that signals from visual motion processing may affect audition relatively directly, without requiring higher-level interpretative processes. While some popular explanations of synaesthesia assume rare and specific patterns of brain hyper-connectivity, the apparently high prevalence of vEAR, and its broad association with other synaesthesias and traits, are consistent with a common dependence on normal variations in physiological mechanisms of disinhibition or excitability of sensory brain areas and their functional connectivity, rather than just on specific patterns of hyper-connectivity. The prevalence of vEAR makes it easier to test such hypotheses further, and makes the results more relevant to understanding not only synaesthetic anomalies but also normal perception.
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