Visual contribution to postural stability: Interaction between target fixation or tracking and static or dynamic large-field stimulus.
Stationary visual information has a stabilizing effect on posture, whereas moving visual information is destabilizing. We compared the influence of a stationary or moving fixation point to the influence of stationary or moving large-field stimulation, as well as the interaction between a fixation point and a large-field stimulus. We recorded body sway in 20 healthy subjects who were fixating a stationary or oscillating dot (vertical or horizontal motion, 1/3 Hz, +/-12 degrees amplitude, distance 96 cm). In addition, a large-field random dot pattern (extension: approximately 80 x 70 degrees) was stationary, moving or absent. Visual fixation of a stationary dot in darkness did not reduce antero-posterior (AP) sway compared to the situation in total darkness, but slightly reduced lateral sway at frequencies below 0.5 Hz. In contrast, fixating a stationary dot on a stationary large-field pattern reduced both AP and lateral body sway at all frequencies (0.1-2 Hz). Ocular tracking of the oscillating dot caused a peak in body sway at 1/3 Hz, i.e. the stimulus frequency, but there was no influence of large-field stimulus at this frequency. A stationary large-field pattern, however, reduced AP and lateral sway at frequencies between 0.1 and 2 Hz when subjects tracked a moving dot, compared to tracking in darkness. Our results demonstrate that a stationary large-field pattern has a stabilizing effect in all conditions, independent of whether the eyes are fixing on a stationary target or tracking a moving target.
Neurology Department, Zürich University Hospital, Switzerland. jean.laurens@gmail.com
J
J
Laurens
L
L
Awai
C J
CJ
Bockisch
S
S
Hegemann
H J A
HJ
van Hedel
V
V
Dietz
D
D
Straumann
D000328:Adult; D000704:Analysis of Variance; D005133:Eye Movements; D005260:Female; D005403:Fixation, Ocular; D006801:Humans; D008297:Male; D008875:Middle Aged; D009039:Motion Perception / Q000502:physiology*; D010775:Photic Stimulation; D004856:Postural Balance / Q000502:physiology*