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Biomedical subjects

T L Harrington

Publications and source records attributed to T L Harrington.

8 recordsLinked to original sources
PubMed1989

A method of stereoptically simulating manifolds of three-dimensional objects using only a single display pattern: a shape-depth-texture invariance.

A means of conceptualizing and generating visual displays that are "self-stereoptic manifolds" is described. First, single patterns that can replace pairs of stereograms to produce illusions of depth are defined and an example is shown. Patterns such as these produce illusory three-dimensional objects hanging in space before or behind the display surface. It is further demonstrated geometrically that such a display actually has three-dimensional information embedded in it peculiar to each of a family, or manifold, of objects that can be experienced one at a time. Each object of the family appears when the viewer looks in space where it "exists." The others remain invisible unless their locations are fixated. If any member of a specific manifold of three-dimensional illusory objects is physically duplicated as a real object and textured in the same way that the illusory object appeared to be, then this new real object will, in turn, generate an illusion of each of the other objects of the manifold when the observer fixates in space where each "exist." Also, if then the viewer looks where the original display previously was, the newly constructed object will disappear and the display will reappear. The geometry and the advantages and disadvantages in relation to a stereoptic pair are discussed.

Depth Perception↗
PubMed1985

Neural mechanisms of space vision in the parietal association cortex of the monkey.

Functional properties of visual and eye-movement-related neurons of area 7a were studied in alert behaving monkeys. Visual fixation (VF) neurons had selectivity in the direction and/or distance of gaze, signaling the spatial position. Visual tracking (VT) neurons had selectivity in the direction of movement, signaling the movement in space. Many passive visual (PV) neurons were suppressed during eye movement, discriminating real from "self-induced" movement. A group of PV neurons sensitive to the depth movement responded to the changing image size. A group of neurons sensitive to the rotation of visual stimulus in space were also found in area 7a.

Animals↗
PubMed1985

Perception of orientation of motion as affected by change in divergence of texture, change in size, and in velocity.

When there is relative motion between an observer and a textured surface such as the ground, motion-related visual information is available about the orientation of the surface through vergence of the paths of the elements of the texture, change in their sizes and in their velocities. This experiment determined the perceptual effectiveness of each variable in foveal and peripheral viewing for producing perceptions of three-dimensional motion. The three variables were electronically separated and displayed singly, in all possible pairs, and all together. Subjects communicated their perceptions of degree of perceived surface tilt at the top, bottom, and middle of the display for the eight different combinations of variables because, during pilot work perceived surface bendings were frequently noted where top, bottom, and middle appeared tilted to different extents. All three variables can lead to relatively reliable perceptions of perceived orientation of the plane of motion, with change in velocity being the most powerful determiner. Change in size was the weakest. Certain combinations can lead to perceptions of extreme warping and should be avoided in motion displays. Subjects consistently underestimate the amount of simulated tilt. Foveal viewing was more accurate than peripheral viewing but peripheral performance was adequately consistent as an input channel for some orientation tasks.

Depth Perception↗
PubMed1983

Divergence thresholds as functions of temporal separation, spatial separation, and retinal locus.

Human thresholds were measured for the detection of angular divergence between straight lines using pairs of line segments. The dependence of these thresholds on temporal separation between the two lines, spatial separation, and retinal locus was assessed. Results were comparable to prior divergence thresholds obtained by Harrington and Harrington in their study of "blur patterns." In blur patterns motion parameters may be processed partly or wholly as form information rather than as motion information per se. Harrington and Harrington had used moderate blurring velocities, for which information on both motion and form were present. Observers may have been responding either to motion or to form. The study reported here used briefly presented two-line "blur patterns" with only form information. Analysis suggested that the form components of fast motion-produced blur patterns could be processed by the human visual system. Neither temporal nor spatial separation was a significant determiner of thresholds in accordance with Harrington and Harrington who found no effect of blur-line density in the range studied. Retinal locus was a factor as it was with blur patterns. Some possible mechanisms for the detection of divergence indicated by these results are discussed.

Discrimination Learning↗
PubMed1981

Perception of motion using blur pattern information in the moderate and high-velocity domains of vision.

A series of studies of visual orientation at blurring velocities is integrated ans summarized. Surfaces moving rapidly in depth were simulated and sensitivities of observers to depth-related geometric parameters of the resulting blur patterns, such as divergence and curvature, were measured. Examples of some ecological analyses of these parameters as sources of visual orientation information are given. The results indicate that human sensitivity to a number of blur pattern variables is high enough to be useful in guidance of locomotion. It was also found that some of the information about motion contained in blur patterns may actually be form information. It appears that visual motion processing may involve a complex interplay of visual form and motion analysing systems.

Discrimination, Psychological↗