title: Independent sources of anisotropy in visual orientation representation: a visual and a cognitive oblique effect.
abstract: The representation of visual orientation is more accurate for cardinal orientations compared to oblique, and this anisotropy has been hypothesized to reflect a low-level visual process (visual, "class 1" oblique effect). The reproduction of directional and orientation information also leads to a mean error away from cardinal orientations or directions. This anisotropy has been hypothesized to reflect a high-level cognitive process of space categorization (cognitive, "class 2," oblique effect). This space categorization process would be more prominent when the visual representation of orientation degrades such as in the case of working memory with increasing cognitive load, leading to increasing magnitude of the "class 2" oblique effect, while the "class 1" oblique effect would remain unchanged. Two experiments were performed in which an array of orientation stimuli (1-4 items) was presented and then subjects had to realign a probe stimulus within the previously presented array. In the first experiment, the delay between stimulus presentation and probe varied, while in the second experiment, the stimulus presentation time varied. The variable error was larger for oblique compared to cardinal orientations in both experiments reproducing the visual "class 1" oblique effect. The mean error also reproduced the tendency away from cardinal and toward the oblique orientations in both experiments (cognitive "class 2" oblique effect). The accuracy or the reproduced orientation degraded (increasing variable error) and the cognitive "class 2" oblique effect increased with increasing memory load (number of items) in both experiments and presentation time in the second experiment. In contrast, the visual "class 1" oblique effect was not significantly modulated by any one of these experimental factors. These results confirmed the theoretical predictions for the two anisotropies in visual orientation reproduction and provided support for models proposing the categorization of orientation in visual working memory.
authors.affiliation: Laboratory of Sensorimotor Control, University Mental Health Research Institute, 11528, Athens, Greece.|Department of Philosophy and History of Science, National and Kapodistrian University of Athens, Athens, Greece.
authors.forename: Panagiota
authors.initials: P
authors.lastname: Balikou
authors.affiliation: Laboratory of Sensorimotor Control, University Mental Health Research Institute, 11528, Athens, Greece.|Biostatistics Department, Medical Directorate, Hellenic National Defense General Staff, Athens, Greece.
authors.forename: Pavlos
authors.initials: P
authors.lastname: Gourtzelidis
authors.affiliation: Neurology Department, Medical School, Aeginition Hospital, National and Kapodistrian University of Athens, Athens, Greece.
authors.forename: Asimakis
authors.initials: A
authors.lastname: Mantas
authors.affiliation: Department of Philosophy and History of Science, National and Kapodistrian University of Athens, Athens, Greece.
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Moutoussis
authors.affiliation: Neurology Department, Medical School, Aeginition Hospital, National and Kapodistrian University of Athens, Athens, Greece.
authors.forename: Ioannis
authors.initials: I
authors.lastname: Evdokimidis
authors.affiliation: Laboratory of Sensorimotor Control, University Mental Health Research Institute, 11528, Athens, Greece. smyrnis@med.uoa.gr.|Psychiatry Department, Medical School, Aeginition Hospital, National and Kapodistrian University of Athens, Athens, Greece. smyrnis@med.uoa.gr.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Smyrnis
mesh_terms: D000328:Adult; D016880:Anisotropy; D003071:Cognition / Q000502:physiology*; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology; D009949:Orientation / Q000502:physiology*; D010775:Photic Stimulation; D011237:Predictive Value of Tests; D014796:Visual Perception / Q000502:physiology*
keywords: Attention; Generalized additive model for location; Shape and scale; Variable orientation error; Visual orientation accuracy mean orientation error; Visual working memory