Typical EEPs elicited by electrical stimulation of rabbit retina using a 0 .5 ms 50 μ A current pulse. EEPs could be recorded following simultaneous stimulation by channels 1–8 (a, b) and channels 49–56 (c, d). (a and b) show the difference in EEP potential amplitude between the anterior and posterior recording electrodes, respectively. The same convention applies to (c) and (d). The channels in the stimulating electrode arrays were indicated in Figure 2b.