The effects of three stimulus durations on spectral sensitivity of the electroretinogram were examined under moderate light adaptation. The durations were 11, 42, and 109 msec. At a low criterion amplitude of response, the 11-msec duration showed lower sensitivity in the green and blue regions of the spectrum than the two longer durations. At the red end of the spectrum all curves showed elevated sensitivity of approximately equal amounts. For a moderate criterion amplitude, the curves for the various durations retained their relative positions at the shorter wavelengths. At the red end of the spectrum, sensitivity decreased for all durations, but to a greater amount for the two longer durations. For a high criterion response, the 11-msec duration became more sensitive throughout the spectrum; however, it retained a form similar to that for the two longer durations. The curves were presumed to include at least two components: a scotopic process and a red-sensitive process. Possible interpretations of the duration effects on the spectral curves included the Bunsen–Roscoe law and the summation of on- and off-responses.
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