To perceive body movement, nervous system uses multi-sensory cues such as vision, vestibular signals, and somatosensation. Among these multi-sensory modality, previous research reported that pressure sensation from soles and proprioception of leg, that is, lower limb somatosensation are strongly correlated with the perception of motion in standing posture. To determine whether lower limb somatosensory cues contribute to perception of motion in standing posture and which sensation of lower limb plays dominant role, we examined the changes in detection threshold with and without lower limb somatosensory constraints. Six healthy male volunteers (aged 21~ 26 years) were participated. Randomly ordered 33 single sinusoidal acceleration at 0.25Hz with peak magnitude ranged from 0 to 8mG were applied using servo-controlled platform. After each stimulus, subjects reported their perceived direction of motion by pressing hand held buttons. Results showed that reduced lower limb somatosensation significantly increased the perception threshold of linear motion.
Without constraints, mean threshold was 0.82±0.23mG, while it was 1.23±0.35mG with reduced lower limb somatosensation. Moreover, when restrained pressure cues of sole, the threshold more increased than the reduced ankle proprioception condition. The results suggest that without visual cues, perception of the movement direction strongly depends on the lower limb somatosensory information, particularly the cutaneous cues from soles.