It is well known that simultaneous presentation of incongruent audio and visual stimuli can lead to illusory percepts. Recent data suggest that distinct processes underlie non-specific intersensory speech as opposed to non-speech perception. However, the development of both speech and non-speech intersensory perception across childhood and adolescence remains poorly defined. Thirty-eight observers aged 5 to 19 were tested on the McGurk effect (an audio-visual illusion involving speech), the Illusory Flash effect and the Fusion effect (two audio-visual illusions not involving speech) to investigate the development of audio-visual interactions and contrast speech vs. non-speech developmental patterns. Whereas the strength of audio-visual speech illusions varied as a direct function of maturational level, performance on non-speech illusory tasks appeared to be homogeneous across all ages. These data support the existence of independent maturational processes underlying speech and non-speech audio-visual illusory effects.

Purpose: Recent studies suggest that cochlear implant (CI) users have a typical, and perhaps improved, ability to fuse congruent multisensory information. The ability to fuse incongruent auditory and visual inputs, however, remains to be fully investigated.Methods: Here, performance on a classical audiovisual task (the McGurk effect) was assessed in seventeen cochlear-implanted, postlingually deaf individuals with varied degrees of auditory competency. Results: In line with previous studies, our results revealed audiovisual fusion abilities that were within normal limits in CI users compared to normally-hearing (NH) participants. A different pattern of response emerged, however, when participants' responses were analyzed according to the degree of auditory proficiency with the CI. Although proficient CI users (pCI) and NH participants favoured auditory input when multisensory signals were not fused, only the non-proficient CI users (npCI) relied predominantly on visual cues to resolve audiovisual conflict. This pattern was found despite a similar percentage of fused percepts between pCI users, npCI users and NH participants. Conclusion: These data show a remarkable level of similarity between pCI users and NH individuals in the perception of incongruent audiovisual information, suggesting that optimal auditory performance with the CI is associated with normal fusion of conflicting audiovisual input.

The presence of a neural mechanism matching execution and observation of actions in the adult human brain is well established. In children, however, description of a resonance motor mechanism is still preliminary. In the present study, we recorded electroencephalographic signals from a subdural 64-contact grid electrode in a 36-month-old child with epilepsy. Spectral analysis was performed on sequences where the child drew with her right hand, watched an experimenter drawing with his right hand or was at rest. Contact sites corresponding to sensorimotor areas were discovered where absolute power was decreased during both observation and execution of hand/arm actions. These data suggest the presence of a mirror neuron system early in the developing brain.