Search PubMed⌕ Search

Biomedical subjects

P Meer

Publications and source records attributed to P Meer.

9 recordsLinked to original sources
PubMed1989

The role of stimulus structure in spatial hyperacuity.

In spatial hyperacuity the subjects discriminate a stimulus feature relative to a reference, with an accuracy significantly better than the grain of the retinal mosaic. We show that the normalized thresholds have a dichotomous behavior; they are either insensitive to the spatial parameter in the experiment or increase very steeply with it. This behavior is explained by the involvement in the processing of pixel (receptor) accuracy information about the structure of the stimulus. A computational model employing optimal filtering reproduces the experimental data and suggests that processing of spatial hyperacuity tasks in the human visual system is optimal.

Computer Simulation↗
PubMed1986

Importance of global information in vernier acuity.

Noisy vernier configurations were generated by normally distributing the lateral displacements of dot elements forming vertical dotted lines. Observations with noisy configurations were compared with thresholds obtained with noise-free lines. In configurations with gap, we have found, through independent perturbation of the end regions adjacent to the gap, that the entire length of the line was actively processed. In an experiment with noisy abutting lines, the threshold as a function of line length exhibited only a slight upward shift relative to the curve obtained with noise-free configurations. Since it is not possible to interpret all the results through a comparison of local positional information extracted from the stimulus configuration, we conclude that global information is also involved in the processing.

Discrimination, Psychological↗
PubMed1985

Context dependent processing in spatial hyperacuity.

The importance of comparison processes in spatial hyperacuity tasks was investigated by means of a new relative nonalignment discrimination task. Vernier-type configuations nonaligned to either left or right, were presented in succession, and the subject had to decide which configuation exhibited a larger nonalignment. The relative nonalignment thresholds were found to be more strongly dependent on the spatial arrangement of the two lines than the thresholds corresponding to "ordinary" spatial hyperacuity performances. This context dependency is attributed to the active role played in the processing by comparison mechanisms.

Discrimination, Psychological↗