The electrophysiology of the retina ofPeriplaneta americana L.

Intracellularly recorded illumination potentials from retinula cells (probably the green sensitive cells) of the cockroachPeriplaneta show the typical tetraphasic responses to graded intensities of light. In the dark-adapted state, the plateau phase is relatively greater than in the light-adapted state, and, in general, the responses are larger.Angles of acceptance in the light-adapted state are 2.4±0.9 ° SD for the horizontal plane and 2.3±0.6 ° SD for the vertical plane. Angles of acceptance were about three times larger for dark-adapted cells, being 6.7±1.8 ° SD in the horizontal plane and 6.9±1.3 ° SD in the vertical plane.In each state, the visual fields are circularly symmetrical.The pigment movements and the palisade which develops upon dark-adaptation (Butler, 1973b) are the only anatomical features which can account for this change in acuity.The above changes are similar in all ommatidia. Combining these measurements with the map of interommatidial angles (Butler, 1973a) leads to the conclusion that movement perception is not constant in different parts of the eye, and that changes during adaptation have unequal effects on movement perception in different parts of the eye.