Biomedical subjects

E H Adelson

Publications and source records attributed to E H Adelson.

6 recordsLinked to original sources

PubMed1992

Directionally selective complex cells and the computation of motion energy in cat visual cortex.

We applied a set of 1- and 2-bar tests to directionally selective (DS) complex cells in the cat's striate cortex, and compared the responses with those predicted by two computational models. Single-bar responses and 2-bar interactions produce distinctive patterns that are highly diagnostic. The observed responses are quite similar to those predicted by a basic (non-opponent) motion-energy model [Adelson & Bergen (1985) Journal of the Optical Society of America A, 2, 284-299]. However, they are not consistent with an opponent combination of energy models, nor are they consistent with any stage of the classic Reichardt model. In particular, the Reichardt model (as well as opponent combinations of energy models) predicts a separable space-time symmetry in the 2-bar interaction that is not observed in our measurements, while the non-opponent energy model predicts an inseparable, oriented interaction very similar to the measured cortical responses. Comparisons between model and measurements suggest possible mechanisms of spatial receptive-field organization and of nonlinear transformations.

Action Potentials↗

PubMed1992

Vision with equiluminant colour contrast: 2. A large-scale technique and observations.

A simple technique is described for producing large-scale, tritanopic displays. The technique reproduces the various phenomena of vision with equiluminous-colour contrast that have previously been reported with red/green stimuli. It is, however, much less demanding technically, robust against artifacts, and can be used on large-scale scenes. One advantage of the technique is that a piece of blue filter can be used individually by each observer to compare quickly tritanopic and luminance conditions.

Attention↗

PubMed1990

The perceptual buildup of three-dimensional structure from motion.

We present a set of psychophysical experiments that measure the accuracy of perceived three-dimensional (3-D) structure derived from relative motion in the changing two-dimensional image. The experiments are motivated in part by a computational model proposed by Ullman (1984), called the incremental rigidity scheme, in which an accurate 3-D structure is built up incrementally, by considering images of moving objects over an extended time period. Our main conclusions are: First, the human visual system can derive an accurate model of the relative depths of moving points, even in the presence of noise in their image positions; second, the accuracy of the 3-D model improves with time, eventually reaching a plateau; and third, the 3-D structure currently perceived appears to depend on previous 3-D models. Through computer simulations, we relate the results of our psychophysical experiments with the predictions of Ullman's model.

Adult↗

PubMed1988

Early vision and texture perception.

Texture perception has frequently been studied using textures constructed by repeated placement of micropatterns or texture elements. Theories have been developed to explain the discriminability of such textures in terms of specific features within the micropatterns themselves. For example, Beck observed that a region filled with vertical Ts is readily distinguished from one filled with tilted Ts but not from one filled with vertical Ls. He attributed this to the different distribution of oriented line segments present in the former case but not in the latter. However, Bergen and Julesz found that a region of randomly oriented Xs segregated from one filled with randomly oriented Ls, in spite of the identical distribution of oriented line segments in the two cases. They suggested that this discrimination might be based on the density of such features as terminators, corners, and intersections within the patterns. We note here that simpler, lower-level mechanisms tuned for size may be sufficient to explain this discrimination. We tested this by varying the relative sizes of the Xs and the Ls; when they produce equal responses in size-tuned mechanisms they are hard to discriminate, and when they produce different size-tuned responses they are easy to discriminate.

Form Perception↗

PubMed1985

Spatiotemporal energy models for the perception of motion.

A motion sequence may be represented as a single pattern in x-y-t space; a velocity of motion corresponds to a three-dimensional orientation in this space. Motion sinformation can be extracted by a system that responds to the oriented spatiotemporal energy. We discuss a class of models for human motion mechanisms in which the first stage consists of linear filters that are oriented in space-time and tuned in spatial frequency. The outputs of quadrature pairs of such filters are squared and summed to give a measure of motion energy. These responses are then fed into an opponent stage. Energy models can be built from elements that are consistent with known physiology and psychophysics, and they permit a qualitative understanding of a variety of motion phenomena.

Humans↗

PubMed1978

Iconic storage: the role of rods.

The hypothesis that rods mediate iconic storage was tested by presenting letters of one color against a field of another. The colors were chosen to be discriminable only by the cones, only by the rods, or both. Under dark adaptation, the rods had little if any effect on partial-report advantage; however, they were important in determining the phenomenal persistence of the stimulus. Under light adaptation, the rods played no apparent role in either type of persistence.

Afterimage↗