HAPTIC CUES FOR ORIENTATION AND POSTURAL CONTROL IN SIGHTED AND BLINDINDIVIDUALS

Haptic cues from fingertip contact with a stable surface attenuate bod y sway in subjects even when the contact forces are too small to provi de physical support of the body. We investigated how haptic cues deriv ed from contact of a cane with a stationary surface at low force level s aids postural control in sighted and congenitally blind individuals. Five sighted (eyes closed) and five congenitally blind subjects maint ained a tandem Romberg stance in five conditions: (1) no cane; (2, 3) touch contact (<2 N of applied force) while holding the cane in a vert ical or slanted orientation; and (4, 5) force contact (as much force a s desired) in the vertical and slanted orientations. Touch contact of a cane at force levels below those necessary to provide significant ph ysical stabilization was as effective as force contact in reducing pos tural sway in all subjects, compared to the no-cane condition. A slant ed cane was far more effective in reducing postural sway than was a pe rpendicular cane. Cane use also decreased head displacement of sighted subjects far more than that of blind subjects. These results suggest that head movement control is linked to postural control through gaze stabilization reflexes in sighted subjects; such reflexes are absent i n congenitally blind individuals and may account for their higher leve ls of head displacement.