A Multi-Technique Source Localization Approach of “Tactile” Lasers in Peri-Personal Space

Abstract

In an event-related potential (ERP) experiment, laser dots were either projected onto a table such that they appeared in a participant's peripheral field of view (FOV) or they were projected onto the participant's hands that were also placed within their peripheral FOV. An oddball paradigm was utilized where participants had to detect a laser deviant that appeared in a stream of standard laser stimuli. Participants were instructed to fixate on a central crosshair and to selectively attend to their left or right hand. In the hands-off condition, participants' ERPs waveform and topographical iso-potential map analyses revealed a typical contra-lateral primary visual activation. In the hands-on condition, the visual activation obtained in the hands-off condition shifted significantly toward anterior primary somatosensory areas. Localization techniques such as independent components analysis, dipole fitting, and sLORETA yielded results that were convincingly convergent with the ERP waveform and topographical map data. That is, visual laser stimuli appeared to possess tactile qualities when they were projected onto visible haptic regions of participant observers.