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Journal of Experimental Biology 58,585-598 (1973)
Published by Company of Biologists 1973

The Eye Muscle of Calliphora Vomitoria L : II. Transient Responses to Changes in the Intensity of Illumination

JOHN PATTERSON ¹

¹ The Department of Zoology, The University of Newcastle upon Tyne, Newcastle upon Tyne, England; Department of Zoology and Comparative Physiology, Queen Mary College, Mile End Road, London, E1

1. Changes in the intensity of the illumination falling on the compound eye produce transient changes in the interspike interval of the tonic potentials generated by the eye muscle of Calliphora vomitoria. These changes are distinct and frequently different in direction from changes in resting activity produced by light and dark adaptation which have been described previously.

2. The effect of ‘light-on’ at high stimulus intensities is to produce a transient increase in the interspike intervals of the eye-muscle potentials. At lower intensities the result is a transient decrease in the interspike intervals.

3. ‘Light-off’ consistently evokes a decrease in the interspike interval, and the magnitude of the decrease is graded with the logarithm of the preceding light intensity.

4. With high-intensity stimuli changes in the interspike intervals occur within 200 msec of a change in illumination and continue to develop for at least 2 sec. The interspike intervals have returned to near to the pre-stimulus values within 30 sec to 2 min of the onset of the stimulus.

5. The behaviour of the eye-muscle system is described for ‘near-threshold’ stimuli and response ‘threshold’ is found to vary with adapting intensity in a way which illustrates a Weber-Fechner relationship.