Conscious perception of vibration-induced movement illusions: psychophysical and source localization evidences

Tendon vibration is known to induce vivid movement illusions by activating muscle spindles and generating perceptions of limb displacement. Neuroimaging studies suggest that a sensorimotor network mediate the phenomenon, but its functional and psychophysical correlates are understudied. This study aims at qualifying conscious perception of motor illusions across the electrophysiological and psychophysical levels. Fifteen volunteers took part to the study. Electroencephalogram (EEG) has been recorded while vibratory stimulations were applied to flexor tendons of the right forearm. Participants were asked to report whether they felt their hand moving and to qualify those perceptions (strength and duration). Source localization (sLORETA) has been performed on EEG frequency data. At the electrophysiological level, we observed the activation of a frontal-parietal network (decrease of neural oscillations, i.e. upper-alpha) while participants consciously reported motor illusions, with the insular and premotor cortices as main signal generators. At the psychophysical level, illusions showed a complex but consistent profile. Finally, across-levels analyses suggested that superior parietal activity plays an important role in actually experiencing illusions, it being associated to their frequency. The consonance between psychophysical and electrophysiological data suggests that pre-/post-central structures play different roles in defining conscious feeling of movement, even if illusory.