Biomedical subjects

Constance S Royden

Publications and source records attributed to Constance S Royden.

4 recordsLinked to original sources

PubMed2006

Factors affecting curved versus straight path heading perception.

Displays commonly used for testing heading judgments in the presence of rotations are ambiguous to observers. They can be interpreted equally well as motion in a straight line while rotating the eyes or as motion on a curved path. This has led to conflicting results from studies that use these displays. In this study, we tested several factors that might influence which of these two interpretations observers see. These factors included the size of the field of view, the duration of the stimulus, textured scenes versus random-dot displays, and whether or not observers were given a description of their path. The only factor that had a significant effect on path perception was whether or not observers were given instructions describing their path of motion. Under all conditions without instructions, we found that observers responded in a way that was consistent with the perception of motion on a curved path.

Eye Movements↗

PubMed2004

Is precise discrimination of low level motion needed for heading discrimination?

Normal observers judge heading well both when moving in a straight line and when moving along a curved path. Judgments of curved path motion require depth variations in the scene while judgments of straight line heading (pure translation) do not. Here we show that a stroke patient who is impaired in low level 2D motion discrimination tasks and cannot accurately judge 3D structure from motion can accurately judge heading for straight line self-motion. This patient is impaired in judgments of curved path self-motion. This suggests that accurate heading judgments for observer translation do not require accurate 2D motion perception or 3D reconstruction of the scene. Judgments of curved path motion appear more dependent on accurate 2D motion perception.

Aged↗

PubMed2003

A model using MT-like motion-opponent operators explains an illusory transformation in the optic flow field.

Previous studies have shown that a physiologically based model using motion-opponent operators to compute heading performs accurately for simulated observer translations. Here we show how this model can explain an illusory shift in the perceived focus of expansion of a radial flow field that occurs when a field of laterally moving dots is superimposed on a field of radially moving dots. Furthermore, we can use the model to predict the perceptual shift of the focus of expansion for novel visual stimuli. These results support the hypothesis that this illusion results from motion subtraction during the processing of optic flow fields.

Computer Simulation↗

PubMed2002

Computing heading in the presence of moving objects: a model that uses motion-opponent operators.

Psychophysical experiments have shown that human heading judgments can be biased by the presence of moving objects. Here we present a theoretical argument that motion differences can account for the direction of bias seen in humans. We further examine the responses of a computer simulation of a model for computing heading that uses motion-opponent operators similar to cells in the primate middle temporal visual area. When moving objects are present, this model shows similar biases to those seen with humans, suggesting that such a model may underlie human heading computations.

Computer Simulation↗