title: Odd sensation induced by moving-phantom which triggers subconscious motor program.
abstract: Our motor actions are sometimes not properly performed despite our having complete understanding of the environmental situation with a suitable action intention. In most cases, insufficient skill for motor control can explain the improper performance. A notable exception is the action of stepping onto a stopped escalator, which causes clumsy movements accompanied by an odd sensation. Previous studies have examined short-term sensorimotor adaptations to treadmills and moving sleds, but the relationship between the odd sensation and behavioral properties in a real stopped-escalator situation has never been examined. Understanding this unique action-perception linkage would help us to assess the brain function connecting automatic motor controls and the conscious awareness of action. Here we directly pose a question: Does the odd sensation emerge because of the unfamiliar motor behavior itself toward the irregular step-height of a stopped escalator or as a consequence of an automatic habitual motor program cued by the escalator itself. We compared the properties of motor behavior toward a stopped escalator (SE) with those toward moving escalator and toward a wooden stairs (WS) that mimicked the stopped escalator, and analyzed the subjective feeling of the odd sensation in the SE and WS conditions. The results show that moving escalator-specific motor actions emerged after participants had stepped onto the stopped escalator despite their full awareness that it was stopped, as if the motor behavior was guided by a "phantom" of a moving escalator. Additionally, statistical analysis reveals that postural forward sway that occurred after the stepping action is directly linked with the odd sensation. The results suggest a dissociation between conscious awareness and subconscious motor control: the former makes us perfectly aware of the current environmental situation, but the latter automatically emerges as a result of highly habituated visual input no matter how unsuitable the motor control is. This dissociation appears to yield an attribution conflict, resulting in the odd sensation.
authors.affiliation: NTT Communication Science Laboratories, Nippon Telegraph and Telephone Corporation, Morinosato, Atsugi, Kanagawa, Japan.
authors.forename: Takao
authors.initials: T
authors.lastname: Fukui
authors.forename: Toshitaka
authors.initials: T
authors.lastname: Kimura
authors.forename: Koji
authors.initials: K
authors.lastname: Kadota
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Shimojo
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Gomi
mesh_terms: D000328:Adult; D001364:Awareness; D001921:Brain / Q000502:physiology; D003243:Consciousness; D004607:Elevators and Escalators; D005684:Gait; D006801:Humans; D008297:Male; D009039:Motion Perception; D009043:Motor Activity; D009068:Movement; D011597:Psychomotor Performance; D012677:Sensation; D016138:Walking