Comparing lateral modulation and amplitude modulation in phantom sensation

Abstract

Phantom Sensation (PhS) is a tactile illusion in which a single sensation is elicited by stimulating two distant points. That sensation moves continuously between the two stimuli by changing the amplitude ratio. In this paper, we compared PhS for two types of tactile stimuli: lateral modulation (LM) of 20 Hz and amplitude modulation (AM) of 200 Hz. In LM, a stimulus point is moved periodically and laterally by several millimeters. In AM, the pressure is changed periodically at a fixed stimulation point. LM and AM are produced by ultrasound radiation pressure, where the force intensity of LM and AM were changed with the same temporal pattern. The results showed that the continuity and the localization of PhS elicited by LM at 20 Hz were significantly smaller than those elicited by AM at 200 Hz in 18 out of 24 conditions. However, PhS remained in all conditions that we used, regardless of LM or AM, even for an extremely long duration of 7.5 s and a short duration of 0.5 s.