Automatic postural response systems in individuals with congenital total blindness

Area of Science:

• Neuroscience
• Human Physiology
• Sensory Systems

Background:

• The role of vision in maintaining postural balance is well-established.
• However, the impact of lifelong absence of vision on automatic postural responses remains less understood.

Purpose of the Study:

• To investigate the effects of congenital total blindness on automatic postural responses to platform-induced perturbations.
• To compare the postural control strategies of congenitally blind and sighted adults.

Main Methods:

• Nine congenitally blind and nine sighted adults participated.
• Postural responses were elicited by four types of platform displacements (forward/backward translation, toe up/down rotation).
• Electromyography (EMG) signals from leg muscles and reaction times to somatosensory stimuli were recorded.

Main Results:

• No significant differences in EMG latencies of lower extremity muscles were observed between groups.
• Congenitally blind subjects exhibited faster reaction times to somatosensory stimuli, except for toe-down rotations.
• Root mean square (RMS) values for postural sway showed no significant differences, though blind subjects swayed more after backward translations.

Conclusions:

• Automatic postural response systems in humans appear unaffected by the absence of vision from birth.
• These systems are likely hard-wired and rely on non-visual sensory information for postural control.
• Lifelong blindness may influence volitional motor responses rather than automatic postural reflexes.