Summary
The eyes of the crabLeptograpsus variegatus scan continually when the animal walks. The scanning movements are in the horizontal plane, have an amplitude of between 0.1° and 0.3° and a frequency of about 6 Hz if the animal is surrounded by a bright, contrasting visual field. The scanning movements are abolished if the animal is placed in the dark, or blinded. During scanning the two eyes are predominantly in phase with each other. It is proposed that the scanning is the result of a general increase of activity in the oculomotor neurons during walking, which causes the eyes to oscillate at a frequency which is set by the properties of the optokinetic feedback system. It is suggested that the main function of scanning is to prevent visual adaptation.
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I thank the members of the Department of Neurobiology for many helpful discussions relating to this study, and Roger Hardie for making the recordings from crab retinula cells, the results of which are referred to in the discussion.
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Sandeman, D.C. Eye-scanning during walking in the crabLeptograpsus variegatus . J. Comp. Physiol. 124, 249–257 (1978). https://doi.org/10.1007/BF00657056
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DOI: https://doi.org/10.1007/BF00657056