Temporal summation in the receptor potential of the Limulus lateral eye: comparison between retinula and eccentric cells.

Temporal summation and reciprocity (Bloch's law) were studied in the receptor potential recorded from the retinula and eccentric cells of the excised Limulus lateral eye. Taking the peak of the receptor potential as the response measure yielded critical durations that ranged between 65 and 170 msec, depending on the cell type and the criterion level of response. At high but not at low response levels, the critical duration is significantly longer in eccentric cells than in retinula cells. Deviations from Bloch's law were found; these deviations were largest at intermediate response levels.