Fig. 4. Average intensity—response curves showing the effect of injection of Ringer's solution into the contralateral optic lobe on light-induced responses of medulla bilateral neurons (MBNs) during day (A) and night (B). Filled circles indicate activity before injection and open circles after injection. Vertical bars indicate ±1 S.E.M. Administration of Ringer's solution had little effect on MBN photo-responsiveness with the suppression index SI=1.4±2.3 (mean ± S.E.M., N=6) and 5.2±1.3 (N=8) for day and night, respectively.