Background and aims: Excitability of pain-processing areas and response to incoming somatosensory stimuli are abnormally enhanced in Fibromyalgia(FM). To explore if such facilitation represents a more general sensorial activation not strictly related to pain, we evaluated excitability of visual cortex, an area not directly involved in pain processing, through Sound-Induced Flash Illusion(SIFI)(1). SIFI are cross-modal illusions, strictly dependent upon visual excitability, where visual perception is influenced by auditory input. When a single flash is accompanied by multiple beeps, it is perceived as multiple flashes(fission illusion), conversely when 2 flashes are accompanied by one beep, they are perceived as one (fusion illusion). SIFI are reduced when visual cortical excitability increases.
Methods: We performed SIFI in 19(18 F)  FM patients and 24 healthy controls(16 F). Throughout the test, 0 -4 flash were presented on a monitor together with 0-4 beeps delivered by loud-speakers, in different combinations. The observer’s task was to judge the number of flashes seen.
Results: Preliminary data show a highly significant reduction in fission illusions in FM patients compared to healthy controls(particularly when 1 flash is accompanied by three or four beeps, p<.0005).
Conclusions: Our results suggest an increased visual excitability that could favor the hypothesis of a general sensorial activation, non strictly linked to pain, in FM. This could make more light on pathophysiological mechanisms of disease likely opening also new ways for treatment. SIFI represent an easy and effective tool to explore cross-modal audio-visual perception and visual cortical excitability in FM patients.

1.Shams et al. Nature.2000,408:788

Note: authors of this abstract have nothing to disclose.

VISUAL CORTICAL EXCITABILITY IN FIBROMYALGIC PATIENTS: A STUDY WITH SOUND INDUCED FLASH ILLUSION