Fig. 4. (A) Response of a POL1-neurone to selective stimulation of different parts of the dorsal rim area (DRA). Left, stimulus situation; right, response traces. The dorsal part of the eye was illuminated with a slit of blue light (150µm wide, 443nm) stimulating a frontal, middle or posterior section of the dorsal rim area (which is represented schematically as in Fig.2C), and the e-vector orientation was rotated forwards and backwards by 360° (see ascending and descending line below the response traces). Note that the POL1-neurone responds to all three modes of stimulation, showing maximal activity at the same e-vector orientation (see vertical grey lines connecting the response traces). (For details of the electrophysiological recording technique, see Petzold, 2001.) (B) Neural integration in POL1-neurones. Interpretation of both the selective stimulation experiments as exemplified in A and the threshold stimulation experiments shown in Fig.3. (i) All three e-vector types of POL1-neurone (represented by the coloured, double-arrowed circles) receive input from a large number of ommatidia along the whole dorsal rim area. (ii) Each e-vector type receives input from ommatidia of appropriate orientation, as exemplified by the coloured T symbols in each box (compare enlarged cross-section through an ommatidum at the lower right).