Visuotactile Peripersonal Space in Healthy Humans: Evidence from Crossmodal Congruency and Redundant Target Effects

Single neuron studies on monkeys provided convincing evidence for the existence of visuotactile peripersonal space. The range of this space was operationally defined as a space where visuotactile interactions occurred at the neuronal level, and the distance between the body part and visual stimuli was a crucial factor. While the functional similarities in humans were mainly evidenced by studies with patients with right brain damage exhibiting extinction, less is known about the same in healthy adults. The present study demonstrated the existence of visuotactile peripersonal space in healthy adults using two psychophysical measurements. In Experiment 1, participants discriminated the location of vibrotactile target stimuli presented on their left or right hand, while trying to ignore visual distractors that were independently presented close to or away from the tactile stimuli, either on the same side as the target stimulus or on the opposite side (visuotactile congruency task). Results showed that crossmodal congruency effects were greater when visual stimuli were in proximity to the hands, rather than away from them. In Experiment 2, redundant target effects were measured by using a go/no-go paradigm where participants produced speeded responses all to randomized sequence of unimodal (visual or tactile) and simultaneous visuotactile targets presented in one hemispace, while ignoring tactile stimuli presented in the other hemispace. Visual targets were presented either close to or away from the hand. Results showed that the statistical facilitation model was violated (i.e., the coactivation model was supported) only when visual stimuli were presented in proximity to the stimulated hand. These results suggest that visuotactile peripersonal space was distinctly and modularly represented in healthy human brains.