Some spatial properties in the first optic ganglion of the fly

Abstract

Spatial properties in the first optic ganglion ofCalliphora stygia were studied electrophysiologically. 1. In the lamina cells, previously described as type I, L1–2 or large unipolar cells, inhibitory processes were demonstrated around the centres of the receptive fields by stimulating with two short slits separated by different distances or one slit with different lengths. Although inhibitory effects were demonstrated by stimulating around the centre of the receptive field, where the largest hyperpolarizing potential was produced, inhibitory effects were not necessarily seen at equal distances in all directions from the centre, but appeared at different distances in different directions. The distances of the inhibitory area from the centre of the receptive field were in the range of 2° to 3.5° in the visual angle. And some directional selectivity in the response was seen, with respect to the orientation of the slit stimuli. 2. A different class of lamina cell (called wide field lamina cell here) with very wide receptive fields (up to 50° or even 70°) could also be recorded intracellularly. The waveform and intensity function of the hyperpolarizing responses elicited in these cells were similar to those of the usually recorded lamina cells mentioned above. Inhibitory phenomena as described above were also demonstrated in cells of this type. The receptive field of this cell type is complex, apparently being primarily excited along three intersecting axes which can be seen to contribute to the directional selectivity of the cell's graded responses to differently oriented slits. In addition, in one cell, depolarizing responses were observed in a pair of restricted areas contained in the opposite angles of two of the intersecting axes. Inhibitory interaction between hyper- and depolarizing responses was demonstrated by simultaneous illumination of both regions.