THIS PAPER presents data which show that the absolute visual threshold for light perception is significantly affected by processes other than retinal photochemistry. Specifically, it will be suggested that fluctuations in the absolute visual threshold are, in part, determined by neural factors. Such a suggestion is consonant with the view that threshold variability reflects physiological fluctuation and not fluctuation in the quantal emission by a stimulus. In other words, it will be maintained that threshold variability lies within the organism and not within the stimulus.
This point of view has been championed by Crozier1 in relation to vision, but it is not held universally. For example, after demonstrating that only one quantum need be absorbed by only 5 to 14 rods of the human retina to produce the visual threshold event in the fully dark-adapted eye, Hecht, Shlaer, and Pirenne2 concluded that "at threshold it is the stimulus
KRIEGER HP. EFFECT OF RETROCHIASMAL LESION UPON VARIABILITY OF THE ABSOLUTE VISUAL THRESHOLD. AMA Arch NeurPsych. 1953;70(1):70-76. doi:10.1001/archneurpsyc.1953.02320310076006