PubMed · 5582459
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
R D Engstrand, G Moeller. 1967. Confusion matrix analysis for form perception.. https://doi.org/10.1177/001872086700900507
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
We assessed the influence of dioptric and diffusive blur on normal subjects' letter and Vernier acuity in two experiments. In the first experiment, letter acuity was measured for isolated black Sloan letters and Vernier acuity was determined for a pair of black vertical abutting or nonabutting lines. Targets were viewed through plus lenses that produced 0, 1, 2, 4, and 8 D of dioptric blur. In the second experiment, letter acuity was determined for bright 4-position Ts and Vernier acuity was measured for a pair of bright abutting vertical lines. Six levels of imposed diffusive blur were produced by varying the distance between a ground glass screen and the oscilloscope on which the targets were presented. The results of both experiments indicate that letter and Vernier acuity for abutting or closely separated lines worsen in parallel curvilinear fashion, as long as the lines comprising the Vernier targets remain equally detectable when various amounts of dioptric and diffusive blur are imposed. We conclude that both dioptric and diffusive blur introduce common processing limitations for letter and Vernier acuity.
Objects can be recognized independently of the view they present, of their position on the retina, or their scale. It has been suggested that one basic mechanism that makes this possible is a memory effect, or a trace, that allows associations to be made between consecutive views of one object. In this work, we explore the possibility that this memory trace is provided by the sustained activity of neurons in layers of the visual pathway produced by an extensive recurrent connectivity. We describe a model that contains this high recurrent connectivity and synaptic efficacies built with contributions from associations between pairs of views that is simple enough to be treated analytically. The main result is that there is a change of behavior as the strength of the association between views of the same object, relative to the association within each view of an object, increases. When its value is small, sustained activity in the network is produced by the views themselves. As it increases above a threshold value, the network always reaches a particular state (which represents the object) independent of the particular view that was seen as a stimulus. In this regime, the network can still store an extensive number of objects, each defined by a finite (although it can be large) number of views.
Contour detection may be mediated by lateral interactions between neighboring cortical neurons whose receptive fields have collinear axes of preferred orientation. This hypothesis was tested in psychophysical experiments and computer simulations using a contour detection task in which observers searched for groups of Gabor patches that followed spatially extended contour paths embedded in noise consisting of several hundred Gabor patches with random positions and orientations. The orientation-selective units in the simulated neural network were linked by facilitatory interconnections whose strength depended on the geometry (distance, curvature, change in curvature) of smooth curves connecting the orientation axes of units in a pairwise fashion. Psychophysical detection performance was much higher for contour signal groups that followed closed rather than open-ended paths. However, just two sudden changes in orientation of neighboring Gabor patch elements in closed-path contours reduced detection performance to the same levels obtained with open-ended contours. These psychophysical data agreed with the results of the neural network simulations. Furthermore, the simulations also accounted for previous findings that removal of a single Gabor patch element from a closed-path contour group significantly degraded detection performance. We conclude that closure alone is not sufficient to enhance the visibility of a contour. However, if a closed contour meets certain geometric constraints, then lateral interactions based on these constraints can generate facilitation that reverberates around the closed path, thereby enhancing the contour's visibility.