Funding. National Institute of Neurological Disorders and Stroke, National Science Foundation
Description. Imagine situations in which you cannot see very well, such as when you enter a darkened room or get up from bed at night to get a drink of water. In these situations, one often seeks out nearby chairs or tables with the fingertips to guide us through the room. However, we have found that lightly touching surfaces offers more than just guidance, it serves to steady upright balance as well.
In a series of experiments that began as a postdoctoal fellow in Dr. James Lackner’s laboratory at Brandeis University, we studied how different levels of force applied through a single fingertip steadies upright balance. People stand while touching a small plate (which measures the applied force) with their right index fingertip. A small alarm is set to go off if too much force is applied. People are told to keep the alarm off. When alarm force levels are set as low as 1 Newton, people find it easy to lightly touch the plate without setting off the alarm. We were initially surprised to find that light touch decreased postural sway as much or more than when subjects applied force at physically supportive levels. Subsequent experiments have shown that light touch is a powerful sensory reference that the nervous system can use to stabilize balance. Similar to vision, it provides information primarily about the velocity of body sway which the nervous system uses to improve its estimate of body dynamics.
Lackner, J.R., DiZio, P., Jeka, J.J., Horak, F.H., Krebs, D. & Rabin, E. (1999). Precision contact of the fingertip reduces postural sway of individuals with bilateral vestibular loss. Experimental Brain Research, 126, 459-466.
Schöner, G.S., Dijkstra, T.M.H., & Jeka, J.J. (1998). Action-perception patterns emerge from coupling and adaptation. Ecological Psychology, 10(3-4), 323-346
Jeka, J.J., Oie, K.S., Schöner, G.S., Dijkstra, T.M.H., & Henson, E. (1998). Position and velocity coupling of postural sway to somatosensory drive. Journal of Neurophysiology. 79, 1661-1674.
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Jeka, J.J., Ribeiro, P., Oie, K.S. & Lackner, J.R. (1998). The structure of somatosensory information for human postural control. Motor Control, 2(1), 13-33.
Jeka, J.J. (1997). Light touch contact as a balance aid. Physical Therapy, 77 (5), 476-487.
Jeka, J.J., Schöner, G.S., Dijkstra, T.M.H., Ribeiro, P. & Lackner, J.R. (1997). Coupling of fingertip somatosensory information to head and body sway. Experimental Brain Research, 113, 475-483.
Jeka, J.J., Easton, R.D., Bentzen, B.L., & Lackner, J.R. (1996). Haptic cues for postural control in sighted and blind individuals. Perception & Psychophysics, 58(3), 409-423.
Jeka, J.J. & Lackner, J.R. (1995). The role of haptic cues from rough and slippery surfaces in human postural control. Experimental Brain Research, 103, 267-276.
Jeka, J.J. & Lackner, J.L. (1995). Fingertip touch as an orientation reference for human postural control. In T. Mergner & F. Hlavacka (Eds.), Multisensory control of posture and movement (p. 213-221). New York: Plenum.
Jeka, J.J. & Lackner, J.R. (1994). Fingertip contact influences human postural control. Experimental Brain Research, 100, 495-502.
Keywords: Light touch, fingertip, balance, sensory, posture control