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I Rentschler

Publications and source records attributed to I Rentschler.

At least 19 recordsLinked to original sources
PubMed1991

Contrast thresholds for identification of numeric characters in direct and eccentric view.

Aubert and Foerster (1857) are frequently cited for having shown that the lower visual acuity of peripheral vision can be compensated for by increasing stimulus size. This result is seemingly consistent with the concept of cortical magnification, and it has been confirmed by many subsequent authors. Yet it is rarely noted that Aubert and Foerster also observed a loss of the "quality of form." We have studied the recognition of numeric characters in foveal and eccentric vision by determining the contrast required for 67% correct identification. At each eccentricity, the lowest contrast threshold is achieved with a specific stimulus size. But the contrast thresholds for these optimal stimuli are not independent of retinal eccentricity as cortical magnification scaling would predict. With high-contrast targets, however, threshold target sizes were consistent with cortical magnification out to 6 degrees eccentricity. Beyond 6 degrees, threshold target sizes were larger than cortical magnification predicted. We also investigated recognition performance in the presence of neighboring characters (crowding phenomenon). Target character size, distance of flanking characters, and precision of focusing of attention all affect recognition. The influence of these parameters is different in the fovea and in the periphery. Our findings confirm Aubert and Foester's original observation of a qualitative difference between foveal and peripheral vision.

Adult↗
PubMed1989

Perceptual spatial frequency--orientation surface: psychophysics and line element theory.

We have investigated the discriminability of gratings which simultaneously vary in spatial frequency and orientation. Thirteen and nine reference gratings were used with two observers, and bivariate discrimination probability surfaces were determined around each grating. These data were then fitted to a general bivariate Gaussian function. The results clearly demonstrate local separability in this log frequency and orientation discrimination domain. Our results also show that the factor contributing most to the non-Euclidean nature of such frequency/orientation discrimination is orientation anisotropia, although we also find some evidence for smaller changes in the associated Riemannian line-element at different frequency ranges. These results cast doubt upon claims for a "pseudo line-element" for frequency discrimination based upon the nonlinear outputs of a fixed set of detectors.

Discrimination, Psychological↗
PubMed1988

On the discrimination of compound Gabor signals and textures.

We compared the discrimination of compound Gabor signals when presented pairwise and in isolation to that of textures consisting of an array of such signals. Textures composed of mirror-image compound Gabor signals were found indistinguishable even when the individual micropatterns were easily discriminated. No such blindness exists for textures composed of non-mirror-image compound Gabor signals. These results are analogous to earlier findings concerning the foveal and extrafoveal rapid discrimination of compound gratings [Rentschler and Treutwein, Nature 313, 308-310 (1985)]. This suggests that both texture perception and extrafoveal vision are, under the conditions of the given experiments, characterized by the absence of neural interactions that otherwise allow the analysis of form. Our results do also imply that the texton concept of Julesz can be extended to grey-level Gabor textures, irrespectively of whether the space domain (geometric features) or the spatial frequency domain (local spectral characteristics) representations of the micropatterns are referred to.

Discrimination, Psychological↗
PubMed1987

Visual pattern recognition in humans. I. Evidence for adaptive filtering.

We have investigated how observers learn to classify compound Gabor signals as a function of their differentiating frequency components. Performance appears to be consistent with decision processes based upon the least squares minimum distance classifier (LSMDC) operating over a cartesian feature space consisting of the real (even) and imaginary (odd) components of the signals. The LSMDC model assumes observers form prototype signals, or adaptive filters, for each signal class in the learning phase, and classify as a function of their degree of match to each prototype. The underlying matching process can be modelled in terms of cross-correlation between prototype images and the input sample.

Form Perception↗
PubMed1986

Cross-correlation model for pattern acuity.

We have investigated whether the perceptual alignment of two images can be predicted from their cross-correlation characteristics. Results from two experiments demonstrate this to be the case with a variety of images varying from Gaussian-modulated sinusoid gratings to two-dimensional textures and face images.

Data Display↗
PubMed1986

On the discrimination of micropatterns and textures.

The Perceptron-type of approach of texture perception argues for decomposition of the patterns by detectors or filters which can interact to result in classification of spatial information. We consider a case of texture discrimination where textures composed of discriminable grey-level micropatterns may or may not be distinguished. Two types of models involving linear pattern decomposition are shown to be insufficient for explaining such results. This suggests that observers encode the signals by means of signal dependent or adaptive feature extractors. Such a concept of texture perception is related to connectionist ideas of information processing as pursued by Julesz in his texton theory.

Animals↗
PubMed1986

Steady-state pattern VEP uncorrelated with suprathreshold contrast perception.

Campbell and Maffei (1970) reported a linear relationship between the logarithm of the grating pattern contrast and the amplitude of the visual evoked response (VEP). This enabled them to predict the pattern visibility by extrapolating to zero amplitude. By using a new digital fast sweep technique for acquiring and analysing steady state evoked potentials we show that, at clearly suprathreshold contrast levels, such a linear relationship only exists for certain spatial frequencies. In general, the VEP saturates with increasing contrast in a way that critically depends on stimulus spatial frequency. Such a dependency on spatial frequency is not obtained for suprathreshold contrast perception which is characterized by a remarkable contrast constancy. Thus the amplitude of the pattern VEP does not convey information about visual perception other than contrast detection thresholds.

Animals↗
PubMed1985

Amblyopic processing of positional information. Part I: Vernier acuity.

Psychometric functions for the recognition of vernier displacements have been measured in 6 strabismic amblyopes, 1 anisometropic amblyope, and 1 bilateral amblyope of unknown aetiology. In the non-amblyopic eyes of the 7 unilateral amblyopes the mean threshold vernier offset was about half of that of a group of 7 experienced normal observers. No correlation was found between vernier acuities and Snellen acuities in the abnormal eyes of squinters. These eyes also displayed massive distortions of horizontal spatial values causing perceptual distortions. In all but one of the amblyopic eyes tested hyperacuity virtually disappeared at the brief exposure duration of 50 ms. None of the observed effects could be predicted from the amblyopic contrast sensitivities, grating resolutions, or letter acuities. This suggests that the loss of positional information is an independent and most significant feature of amblyopic visual dysfunction.

Amblyopia↗
PubMed1985

Amblyopic processing of positional information. Part II: Sensitivity to phase distortion.

Amblyopic sensitivities to spatial distortions of compound gratings and checker-board textures were studied. Iso-energy target signals were used by employing phase modulations which leave the stimulus power spectra unaltered. The non-amblyopic eyes of the 6 amplyopes tested showed supranormal sensitivities at 1 s exposure duration for both types of patterns. At 125 ms the amblyopic eyes were found virtually blind to the texture distortions while performance improved with prolonging the presentation time to 1 s. Comparable results were obtained with compound gratings. However, the correlation between amblyopic acuities and texture discrimination was higher than that between acuities and grating performance. This is probably due to the fact that both (misaligned) vernier targets and the texture are more 'natural' stimuli in the sense that they contain a broad range of spatial frequency components at many different orientations. Differences in behaviour between strabismic and anisometropic amblyopes did not occur. This suggests that the results depend upon defects of foveal visual function.

Amblyopia↗
PubMed1985

Hidden-face recognition: comparing foveal and extrafoveal performance.

Ambiguous stimulus material was computer-generated by superimposing image components of a target-face and either a random checkerboard texture or a masking face. The recognition of the target-face was studied both for foveal and extrafoveal vision. Compensation of the peripheral disadvantage in image discrimination by rescaling the stimulus size was possible only in the case of texture. Comparable results were obtained from combining band-pass image components of the portraits. Results suggest that it is the relative inability to recover a signal from spatially correlated noise that characterizes visual discrimination in the peripheral visual field.

Adult↗
PubMed1979

Abnormal orientation selectivity in both eyes of strabismic amblyopes.

In normal observers preadaptation to a parallel grating increases the contrast threshold for a line whereas a perpendicular grating has no effect. Such orientation selectivity was not found in the amblyopic eye of two out of five squinters. Only a weak after-effect produced with a grating parallel to the line was obtained in the good eye of four of the amblyopes while all of them show an abnormal threshold reduction following adaptation to a perpendicular grating. This suggests a relationship between abnormal binocular interaction during visual development and the organization of orientational mechanisms but does not explain the loss of visual acuity in amblyopia.

Adaptation, Ocular↗
PubMed1978

Accuracy of evoked potential refractometry using bar gratings.

We recorded cortical potentials evoked by phase-alternating square-wave gratings. Significant effects of varying the refractive power of the eye are obtained only at 5 cycles/degree (cy/deg) and above. The extrapolation to zero amplitude of the evoked response as a function of spatial frequency predicts the psychophysical visual acuity even for the myopic eye. As the sensitivity of meridional refraction using sufficiently fine bar gratings is better than 0.5 D it provides a suitable means for the measurement of astigmatism.

Astigmatism↗