The spatiotemporal dynamics of the sound-induced flash illusion : A systematic review of event-related potential studies

Sammanfattning

Multisensory integration allows the brain to combine information across the senses. For decades, integration was viewed through the lens of visual dominance when our senses are presented with conflicting information. The sound-induced flash illusion (SIFI) challenged this view and demonstrated that the auditory modality can alter visual activity. The SIFI has two variants: the fission illusion, in which one flash paired with two beeps is perceived as two flashes, and the fusion illusion, in which two flashes paired with one beep are perceived as one. Audiovisual cross-modal activity seems to arise very early in the processing stream which can potentially explain audiovisual illusions such as the SIFI. This systematic review synthesised event-related potential (ERP) evidence of the SIFI in both of its variants, fission and fusion, in a healthy population. A total of five studies fulfilled the inclusion criteria and were included in the review. The synthesised ERP evidence suggests that the early cross-modal interactions underlying the SIFI can be explained by direct activity between modality-specific cortices rather than by higher-order feedback alone, with later components reflecting both general audiovisual integration and illusion-specific processing. The fission and fusion variants appeared to share the superior temporal gyrus (STG) as a common mediator but with opposite directions of effect and different timing of visual-cortex involvement, suggesting they are separable at the neural level.