Expectation of tactile events is enough to induce crossmodal congruency effect (CCE)

Abstract

New approaches understand sensory processing as constructive and active in nature. Expectations about upcoming sensory events can be utilized to prepare sensory cortices by instantiating a neural context that allows for enhanced processing of the forthcoming event. But, how deeply is expectation involved in sensory processing? One of the most useful ability of our brain is to integrate input from different sensory modalities in order to create a coherent representation of the environment. Does expectation have a role to play in basic crossmodal integration? In this study we tackled this issue by taking advantage of a Crossmodal Congruency Task. Participants were stimulated at the index or thumb of the right hand, using solenoids mounted on a foam cube. Simultaneously they received a visual stimulus adjacent to the active solenoid (congruent) or adjacent to the inactive solenoid (incongruent). The task was to respond to the elevation of the visual stimulus while ignoring the tactile distractor. To induce expectation over the tactile stimulus, in 80% of the trials either a high or a low pitched tone preceded the stimulation of the index and thumb finger, respectively. In the remaining 20% of the trials the tactile stimulus was not delivered. Results fully replicated basic CCE. Strikingly, CCE was observed, though at a less degree, also when the tactile stimulus was not delivered but merely expected. Our findings suggest that a coherent representation of the environment, as achieved by crossmodal integration, does not require real stimuli. Expected stimuli are enough to this aim.