The sound-induced phosphene illusion

Nadia Bolognini, Silvia Convento, Martina Fusaro, Giuseppe Vallar

Research output: Contribution to journalArticlepeer-review


Crossmodal illusions clearly show how perception, rather than being a modular and self-contained function, can be dramatically altered by interactions between senses. Here, we provide evidence for a novel crossmodal "physiological" illusion, showing that sounds can boost visual cortical responses in such a way to give rise to a striking illusory visual percept. In healthy participants, a single-pulse transcranial magnetic stimulation (sTMS) delivered to the occipital cortex evoked a visual percept, i.e., a phosphene. When sTMS is accompanied by two auditory beeps, the second beep induces in neurologically unimpaired participants the perception of an illusory second phosphene, namely the sound-induced phosphene illusion. This perceptual "fission" of a single phosphene, due to multiple beeps, is not matched by a "fusion" of double phosphenes due to a single beep, and it is characterized by an early auditory modulation of the TMS-induced visual responses (~80 ms). Multiple beeps also induce an illusory feeling of multiple TMS pulses on the participants' scalp, consistent with an audio-tactile fission illusion. In conclusion, an auditory stimulation may bring about a phenomenological change in the conscious visual experience produced by the transcranial stimulation of the occipital cortex, which reveals crossmodal binding mechanisms within early stages of visual processing.

Original languageEnglish
Pages (from-to)469-478
Number of pages10
JournalExperimental Brain Research
Issue number4
Publication statusPublished - Dec 2013


  • Auditory
  • Crossmodal
  • Occipital cortex
  • TMS
  • Visual

ASJC Scopus subject areas

  • Neuroscience(all)


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