title: Velocity of motion across the skin influences perception of tactile location.
abstract: We investigated the influence of motion context on tactile localization, using a paradigm similar to the cutaneous rabbit or sensory saltation (Geldard FA, Sherrick CE. Science 178: 178-179, 1972). In one of its forms, the rabbit stimulus consists of a tap in one location quickly followed by another tap elsewhere, creating the illusion that the two taps are near each other. Instead of taps, we used position of a halted brush and instead of distance judgment, localization responses. The brush moved across the skin of the left forearm, creating a clear motion signal before and after a rabbitlike leap of 10 cm (at 100 cm/s). Three before-and-after velocities (7.5, 15, or 30 cm/s) were used. Participants (n = 13) pointed with their right arm at the felt location of the brush when it halted either 1 cm before or after the leap. These stops were 12 cm apart, but distances computed from localization responses were only 5.4, 6.5, and 7.5 cm for the three velocities, respectively (F[2,11] = 15.19, P = 0.001). Thus the leap resulted in compressive position shift, as described previously for sensory saltation, but modulated by motion velocity before the leap: the slower the motion, the greater the shift opposite to motion direction. No gap in stimulation was perceived. We propose that velocity extrapolation causes the position shift: extrapolated motion does not have enough time to bridge the real spatial gap and thus assigns a closer location to the skin on the opposite side of the gap.
authors.affiliation: Faculty of Health Sciences, University of Sydney, Sydney, Australia;
authors.forename: Elizabeth H L
authors.initials: EH
authors.lastname: Nguyen
authors.affiliation: Neuroscience Research Australia, Sydney, Australia; and University of New South Wales, Sydney, Australia.
authors.forename: Janet L
authors.initials: JL
authors.lastname: Taylor
authors.affiliation: Neuroscience Research Australia, Sydney, Australia; and University of New South Wales, Sydney, Australia.
authors.forename: Jack
authors.initials: J
authors.lastname: Brooks
authors.affiliation: Faculty of Health Sciences, University of Sydney, Sydney, Australia; tatjana.seizova-cajic@sydney.edu.au.
authors.forename: Tatjana
authors.initials: T
authors.lastname: Seizova-Cajic
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009038:Motion; D012867:Skin / Q000294:innervation; D012879:Skin Physiological Phenomena; D014110:Touch; D055698:Touch Perception
keywords: completion; local sign; motion interpolation; position shift; somatosensory space