Assessing the oscillatory properties of functional connections between sensory areas during crossmodal illusions: A correlational and causal investigation.

A comprehensive investigation on multisensory integration is presented whereby three complex studies investigating the role of neuro-oscillatory processes in tactile-visual and auditory-visual illusory tasks were conducted. Utilising EEG scanning we first replicated previous evidence of a correlation between individual alpha frequency and the auditory-induced Double Flash Illusion (DFI). We also provided evidence of a previously unreported correlation between individual beta frequency and the corresponding tactile-induced DFI. In two follow-up studies evidence is also provided of a causal relationship between beta processes and the tactile-induced DFI using a variant of paired associative TMS known as cortico-cortical Paired Associative Stimulation. Here we demonstrated by temporarily reducing occipital beta speed we can subsequently produce reliably predictable changes in the temporal profile of visuo-tactile multisensory processing. Using two control measures across two investigations we provided evidence suggesting that the stimulation that we utilised was both frequency specific and hemisphere specific. From this we concluded that multisensory processes are facilitated by the oscillatory properties of network-specific (auditory-to-visual or somatosensory-to-visual) neural connections favouring optimal, directional neural communication and integration between the senses.