Abstract
Orientation selectivity is a fundamental property of primary visual encoding. High-level processing stages also show some form of orientation dependence, with face identification preferentially relying on horizontally-oriented information. How high-level orientation tuning emerges from primary orientation biases is unclear. In the same group of participants, we derived the orientation selectivity profile at primary and high-level visual processing stages using a contrast detection and an identity matching task. To capture the orientation selectivity profile, we calculated the difference in performance between all tested orientations (0, 45, 90, and 135°) for each task and for upright and inverted faces, separately. Primary orientation selectivity was characterized by higher sensitivity to oblique as compared to cardinal orientations. The orientation profile of face identification showed superior horizontal sensitivity to face identity. In each task, performance with upright and inverted faces projected onto qualitatively similar a priori models of orientation selectivity. Yet the fact that the orientation selectivity profiles of contrast detection in upright and inverted faces correlated significantly while such correlation was absent for identification indicates a progressive dissociation of orientation selectivity profiles from primary to high-level stages of orientation encoding. Bayesian analyses further indicate a lack of correlation between the orientation selectivity profiles in the contrast detection and face identification tasks, for upright and inverted faces. From these findings, we conclude that orientation selectivity shows distinct profiles at primary and high-level stages of face processing and that a transformation must occur from general cardinal attenuation when processing basic properties of the face image to horizontal tuning when encoding more complex properties such as identity.
Highlights
We further showed that horizontally-filtered face images trigger the largest response in the Fusiform Face Area (FFA), a high-level visual region responding preferentially to faces ([13]; see [14,15] for EEG evidence of a horizontal dependence of face-specialized neural responses at a latency corresponding to high-level processing stages)
In a Bayesian repeated measures ANOVA we investigated the evidence in favor of the absence (H0) or presence (H1) of any effects of Task (2 levels: Contrast Detection, Face Identification), Stimulus (2 levels: Upright Faces, Inverted Faces), Model (3 Levels: Models 1 and 2 (Model 1), Model 2, Model 3) and all their respective interactions
Our approach shares commonalities with the Representational Similarity Analysis (RSA) framework in that we summarize the empirical data and a priori models in a similar format to analyze the similarity between the patterns observed in the data and the ones predicted by the a priori models [46,47,48,49]
Summary
Our aim was to investigate whether and how the profile of orientation selectivity is modulated by task and stimulus category. We aimed to provide potential answers as well as considerations for future studies into this topic
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