Biomedical subjects

Thomas U Otto

Publications and source records attributed to Thomas U Otto.

3 recordsLinked to original sources

PubMed2006

The flight path of the phoenix--the visible trace of invisible elements in human vision.

How features are attributed to objects is one of the most puzzling issues in the neurosciences. A deeply entrenched view is that features are perceived at the locations where they are presented. Here, we show that features in motion displays can be systematically attributed from one location to another although the elements possessing the features are invisible. Furthermore, features can be integrated across locations. Feature mislocalizations are usually treated as errors and limits of the visual system. On the contrary, we show that the nonretinotopic feature attributions, reported herein, follow rules of grouping precisely suggesting that they reflect a fundamental computational strategy and not errors of visual processing.

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PubMed2006

Perceptual grouping induces non-retinotopic feature attribution in human vision.

The human visual system computes features of moving objects with high precision despite the fact that these features can change or blend into each other in the retinotopic image. Very little is known about how the human brain accomplishes this complex feat. Using a Ternus-Pikler display, introduced by Gestalt psychologists about a century ago, we show that human observers can perceive features of moving objects at locations these features are not present. More importantly, our results indicate that these non-retinotopic feature attributions are not errors caused by the limitations of the perceptual system but follow rules of perceptual grouping. From a computational perspective, our data imply sophisticated real-time transformations of retinotopic relations in the visual cortex. Our results suggest that the human motion and form systems interact with each other to remap the retinotopic projection of the physical space in order to maintain the identity of moving objects in the perceptual space.

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PubMed2006

Perceptual learning with spatial uncertainties.

In perceptual learning, stimuli are usually assumed to be presented to a constant retinal location during training. However, due to tremor, drift, and microsaccades of the eyes, the same stimulus covers different retinal positions on sequential trials. Because of these variations the mathematical decision problem changes from linear to non-linear (). This non-linearity implies three predictions. First, varying the spatial position of a stimulus within a moderate range does not deteriorate perceptual learning. Second, improvement for one stimulus variant can yield negative transfer to other variants. Third, interleaved training with two stimulus variants yields no or strongly diminished learning. Using a bisection task, we found psychophysical evidence for the first and last prediction. However, no negative transfer was found as opposed to the second prediction.

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