Reply to “Comment on ‘Large deflexion of variable-thickness plates’ by A. K. Basu and J. C. Chapman”

Abstract

Potential changes during 5 min periods of light and dark adaptation were recorded in the compound eyes and optic lobes of six insects. In Locusta, Schistocerca, Phormia, and Calliphora there was a rapid negative deflexion at on and a positive deflexion at off in the retinula cell region. During steady illumination the potential diminished and reached a steady level in 5 min. In Locusta the rapid deflexions were abolished when the negative peak potential in the first synaptic region was abolished by trauma or anoxia; and under these conditions only a slow potential change remained. Fast deflexions were not found in the retinula cell region in Aeshna and Periplaneta but only slow potential changes. By studying the effect of light intensity, wavelength, and time of exposure on the locust eye it was found that (a) the amplitude of the rapid on-deflexion was proportional to the logarithm of the incremental intensity, and (b) that the response was maximal in the blue-green part of the spectrum (500 mμ). Rapid deflexions reversed in sign when the electrode was deeper than the first synaptic region, whereas the slow phase of the response did not reverse but became attenuated at greater depths. The potential changes have two stable states; one in darkness and the other in light, each reached after a pronounced but transient overshoot. It is suggested that the fast and slow components of the response have separate origins, the former is dependent on the functional integrity of the first synaptic region whereas the latter may be due to a slow change in the visual pigments. The relationship of the above potential changes to the spike potential discharges in the optic lobe is discussed.