Three-dimensional vestibular eye and head reflexes of the chameleon: characteristics of gain and phase and effects of eye position on orientation of ocular rotation axes during stimulation in yaw direction

J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 2003 Jul;189(7):509-17. doi: 10.1007/s00359-003-0426-y. Epub 2003 May 29.


We investigated gaze-stabilizing reflexes in the chameleon using the three-dimensional search-coil technique. Animals were rotated sinusoidally around an earth-vertical axis under head-fixed and head-free conditions, in the dark and in the light. Gain, phase and the influence of eye position on vestibulo-ocular reflex rotation axes were studied. During head-restrained stimulation in the dark, vestibulo-ocular reflex gaze gains were low (0.1-0.3) and phase lead decreased with increasing frequencies (from 100 degrees at 0.04 Hz to < 30 degrees at 1 Hz). Gaze gains were larger during stimulation in the light (0.1-0.8) with a smaller phase lead (< 30 degrees) and were close to unity during the head-free conditions (around 0.6 in the dark, around 0.8 in the light) with small phase leads. These results confirm earlier findings that chameleons have a low vestibulo-ocular reflex gain during head-fixed conditions and stimulation in the dark and higher gains during head-free stimulation in the light. Vestibulo-ocular reflex eye rotation axes were roughly aligned with the head's rotation axis and did not systematically tilt when the animals were looking eccentrically, up- or downward (as predicted by Listing's Law). Therefore, vestibulo-ocular reflex responses in the chameleon follow a strategy, which optimally stabilizes the entire retinal images, a result previously found in non-human primates.

Publication types

  • Comparative Study

MeSH terms

  • Adaptation, Physiological
  • Animals
  • Darkness
  • Electrooculography
  • Eye Movements / physiology*
  • Head / physiology*
  • Head Movements / physiology*
  • Light
  • Lizards
  • Motion Perception
  • Ocular Physiological Phenomena*
  • Orientation / physiology*
  • Reflex, Vestibulo-Ocular / physiology*
  • Rotation
  • Time Factors