Unit:
Specialty Cognitive NeuroscienceLibrary of the School of Health Sciences
Author:
Apostolakis Antonios
Supervisors info:
Σμυρνής Νικόλαος, Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ, Επιβλέπων
Πόταγας Κωνσταντίνος, Αναπληρωτής Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Ζαλώνης Ιωάννης, Αναπληρωτής Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Original Title:
Μελέτη της ανισοτροπίας αναπαράστασης του χώρου αναφορικά με την οπτική αντίληψη της διεύθυνσης της κίνησης
Translated title:
A study on the anisotropy in the visual representation of motion direction
Summary:
The oblique effect refers to the higher accuracy of the visual system for cardinal (vertical and horizontal) directions rather than oblique ones. It is well-established from previous studies that there are two independent sources of this phenomenon, a “class 1” oblique effect, that has been hypothesized to reflect a low-level visual process, and a “class 2” oblique effect, mirroring higher cognitive processes.
In this study, we investigated the existence of the two sources of this perceptual anisotropy in relation to perception of motion direction. For this purpose, we employed a Random Dot Kinematogram, which is a commonly-used stimulus to study motion perception in vision research, presented on a computer monitor. Each motion stimulus was composed of dots moving in a range of directions, drawn from a Gaussian distribution. Stimulus' noise level was manipulated by varying the standard deviation of dot pattern's direction (0 and 10°). In this type of stimulus, subjects had to integrate the individual dot motions in order to perceive a global motion and its dominant direction.
Directional error (DE) was measured when normal subjects tried to align dot pattern's direction to the direction of a peripheral target located in one of 16 directions equally spaced on the circumference of a circular aperture surrounding the dots. The “class 1” oblique effect was manifested by measuring the variance of DE, which was lower in the alignment for cardinal directions compared to oblique. The “class 2” oblique effect was manifested by measuring mean DE, resulting in a tendency away from cardinal and toward the oblique directions. Only the high-level oblique effect showed significant interaction with stimulus' noise level.
These results highlight the existence of the two independent sources of oblique effect with reference to perception of motion direction and the discrete perceptual system which serves as its substrate.
Main subject category:
Health Sciences
Keywords:
Motion perception, Oblique effect, Visual perception, Space, Anisotropy
Number of references:
143
