THEORY AND MEASUREMENT OF VISUAL MECHANISMS
Open Access
- 19 September 1941
- journal article
- research article
- Published by Rockefeller University Press in The Journal of general physiology
- Vol. 25 (1), 89-110
- https://doi.org/10.1085/jgp.25.1.89
Abstract
For spectral regions associated with violet, blue, green, and red the relation between mean critical flash intensity Im for visual flicker and the flash frequency F is modified as already found with white light when the light time fraction tL in the flash cycle is changed. For a square image 6.13° on a side, foveally fixated, the "rod" and "cone" contributions to the duplex contour are analyzed in the way already used for white. It is pointed out that several customary qualitative criteria for cone functioning do not necessarily give concordant results. The analysis shows that the three parameters of the probability summations giving the "rod" and "cone" curves are changed independently as a function of wave-length composition of the light, and of the light time fraction. The correlation of these changes, and of those found in the associated variability functions, can be understood in terms of differences in (1) the numbers of neural units potentially excitable and (2) in the numbers of elements of neural effect obtained from them. In a multivariate situation of this kind it is necessary to compare intensities of luminous flux required to activate half the total population of potentially available elements when this total size is held constant for the different conditions. The results of this comparison, for the filtered lights used, are discussed in relation to certain aspects of excitation vs. wave-length. The problem is a general one, arising where the effects produced as a function of a particular variable are concerned. In the distinction between (1) units excited and (2) the actions they produce may be found the clue for the curious fact that with certain wave-lengths the critical intensities are lower than for white. The extension of the observations to other parts of the retina may be expected to further this analysis.This publication has 7 references indexed in Scilit:
- On the Law for Minimal Discrimination of IntensitiesProceedings of the National Academy of Sciences, 1940
- TEMPERATURE AND CRITICAL ILLUMINATION FOR REACTION TO FLICKERING LIGHTThe Journal of general physiology, 1940
- Temperature and the Critical Intensity for Response to Visual FlickerProceedings of the National Academy of Sciences, 1940
- The Theory of the Visual ThresholdProceedings of the National Academy of Sciences, 1940
- RODS, CONES, AND THE CHEMICAL BASIS OF VISIONPhysiological Reviews, 1937
- On the Law for Minimal Discrimination of IntensitiesProceedings of the National Academy of Sciences, 1937
- The Influence of Intensity, Color and Retinal Location on the Fusion Frequency of Intermittent IlluminationProceedings of the National Academy of Sciences, 1933