Faculty Research Page

Donald Glaser

Donald Glaser

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Research Interests

Our goal is to construct computational models of the human visual system which explain its performance in terms of its physiology and anatomy.

In vision experiments we present images on computer monitors to subjects who are asked to judge shape, depth, color, velocity, texture, motion, etc. In a recent study of stereopsis, subjects could judge the relative depth of two adjacent test dots in the center of the screen very accurately. Next the "scene" was enclosed in a "picture frame" 50 degrees wide. When the frame was "tilted" in stereo, a systematic bias was discovered in the test dot judgments, even though the subjects didn't know that the frame was being manipulated and couldn't report it correctly. Thus a powerful subliminal cue was at work, not contained in the classical theory of stereopsis. We are working on models to explain this and other mysterious "unclassical" results.

Our recent models of the visual system depend on propagation of excitations in a two-dimensional network of neurons similar to those in the primary visual cortex. These models can detect a single moving dot in a field of thousands of fixed dots, in analogy with our ability to detect an artificial satellite moving against 3000 fixed stars in the night sky, for a signal/noise ratio of 1/3000 and seem to work well also for perception of shape, and depth. They are being developed using the largest unclassified Cray computer in addition to our own desktop machines and also being tested psychophysically. Simulations are essential since conventional mathematics are ill-suited to building a useful bridge between psychophysics and neurobiology.

Current Projects

Our current work is a study of the effect of cortical noise in visual perception.  We have devised displays that stimulate the perception of illusory motion.   Nothing is  moving in these displays, or there is truly random motion of hundreds of black dots on a white background.   Nevertheless viewers report seeing illusory rotary motion in which the direction of rotation reverses spontaneously every 2 or 3 seconds.  If the viewer says silently to himself/herself, I want it to reverse the illusory rotation is seen to reverse.    But if the viewer has any deliberate thought silently, the perceived rotation reverses.   Apparently the mechanism is a perturbation of attention, which leads to a rotation reversal.   We dont fully understand the mechanisms at work, but stochastic resonance seems to play a role.   A number of ongoing psychophysical experiments are telling us  more and more about the processes involved in the triggered rotation reversals and the spontaneous ones.   We are planning MEG experiments to gain more insight into possible mechanisms.

Selected Publications

Motion Detection and Characterization by an Excitable Membrane: The Bow Wave Model. [D. A. Glaser and D. Barch (1999) Neurocomputing 26-27, 137-146]

Depth Discrimination of a crowded line is better when it is more luminant than the lines crowding it. [T. Kumar and D. A. Glaser (1995) Vision Res. 35, 657-666]

Initial performance, learning, and observer variability for hyperacuity tasks. [T.Kumar and D. A. Glaser (1993) Vision Res. 33 (16), 2287-2300]

Metastable motion anisotropy. [A. Chaudhuri and D. A. Glaser (1991) Vis. Neurosci. 7(4), 397-407]

Last Updated 2003-09-05