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Biomedical subjects

D J Lasley

Publications and source records attributed to D J Lasley.

10 recordsLinked to original sources
PubMed1991

Postural stability and stereo-ambiguity in man-designed visual environments.

Our modern rectilinear visual environment contains visual stimuli for which evolution has not had time to optimally shape visual processing. One such stimulus, periodic stripes, is known to lead to visual depth ambiguity. In this paper we show that postural instability, as measured by the variance of fore and aft sway, is increased by viewing such stimuli. This instability may be the precursor of falls. Designers must evaluate the visual impressions conveyed by their systems in order to avoid postural instability due to visual ambiguity.

Adult↗
PubMed1990

Wallpaper illusion: cause of disorientation and falls on escalators.

The wallpaper illusion, first described over a century ago, can occur when a person with normal binocular vision views a pattern that is periodic in the horizontal meridian of the visual field. Escalator trends present such a pattern. Evidence is presented favoring the view that disorientation experienced by escalator riders is caused by this illusion. Possibly some of the estimated 60,000 escalator falls occurring in the United States each year are linked to it.

Accidental Falls↗
PubMed1985

Site of the accelerating nonlinearity underlying luminance-change detection.

The visual psychometric function for luminance-increment detectability (d') is known to be an accelerating function of stimulus energy. Two different models have been suggested to explain this fact and also why a luminance-increment pedestal linearizes the psychometric function. In the present experiment it is shown that a dichoptically presented increment linearizes the psychometric function and facilitates detection of weak signals. Since the dichoptic pedestal combines with the signal centrally, the nonlinearity must then originate more centrally. This result is compatible with the uncertainty model of the nonlinear psychometric function but not with a model that requires a nonlinear transducer.

Humans↗
PubMed1985

Discrimination of crossed and uncrossed disparities.

Tanner's theory of recognition [J. Acoust. Soc. Am. 28, 882 (1956)] was applied to the discrimination of retinal disparity stimuli for both diplopic and fused images. The results for diplopic stereopsis suggest a two-channel model with separate encoding of crossed and uncrossed disparities, similar to the model proposed by Richards [Exp. Brain Res. 10, 308 (1970)]. For fused images the results were consistent with a multichannel model with overlapping disparity sensitivities.

Diplopia↗
PubMed1985

Discrimination of luminance increments and decrements.

Discrimination of pulsed increments from decrements improves relative to detection when the adaptation level is decreased or stimulus duration is increased. Using Tanner's theory of recognition [J. Acoust. Soc. Am. 28, 882 (1956)], we show that the subject's internal decision variables corresponding to the increment and decrement stimuli also show increased statistical independence as adaptation is decreased or stimulus duration increases. We infer from this result that at high adaptation levels detection is based predominantly on information in one channel, whereas at low adaptation levels there is information from two channels. Similarly, for long durations, we infer two independent channels, which contribute little information about the sign of the stimulus at short durations.

Discrimination, Psychological↗
PubMed1985

Visual depth illusion and falls in the elderly.

This article investigates the relation of vision and the effects of age on the maintenance of posture. This relationship in the elderly is explored within the context of visual depth illusions induced by repeating patterns that occur on escalator treads and elsewhere in the environment. Age does not appear to reduce the susceptibility of the elderly to visual depth illusions. However, if age is coupled with declines in motor control and strength, the elderly are probably more susceptible to falls.

Accidents↗
PubMed1976

Binocular vision: two possible central interactions between signals from two eyes.

Both foveae of light-adapted subjects were stimulated at the same time with monocularly presented lights of increasing or decreasing luminance. Combinations judged just detectable violated predictions of the energy summation and the probability summation hypotheses of binocular interaction. Rather, the results can be explained by independent central neural mechanisms that signal the sum or the difference of stimuli to two eyes.

Humans↗