Spatial arrangement of line, edge and grating detectors revealed by subthreshold summation

The present psychophysical experiments provide evidence for the existence of a variety of detectors responding optimally to lines, edges or gratings. Their existence is revealed by subthreshold summation measurements in which the effect of a subthreshold background on the contrast threshold of a test stimulus is determined. By suitable choice of test and background patterns, we have studied the sensitivities of the detectors tuned to a variety of patterns (e.g. lines, edges and gratings) to background patterns also consisting of lines, edges or gratings. The analysis of the measurements is shown to be self-consistent in a number of ways; for example, the measured contrast sensitivity of the line detector for gratings of different frequencies may be used to predict the sensitivity of this detector for fine lines as a function of their width and position. © 1973.