Neural model for shading pathway in biological motion stimuli

Research Area

Neural and Computational Principles of Action and Social Processing

Researchers

Martin A. Giese

Description

Neural models of biological motion perception so far have focused on the processing of features that characterize the 2D structure and motion of the human body. We extend such models for the processing of shading cues in order to analyze the three-dimensional structure of walkers. As extension of a learning-based neural model, we add a ‘shading pathway’ that computes the internal contrast gradients that vary with the 3D view of the walker, even if the silhouette information remains identical. These model neurons are embedded within a recurrent neural field that jointly represents the sequential temporal structure of the stimulus and the view of the walker. The neural field dynamics reproduce the perceptual multi-stability and the spontaneous perceptual switching between stimulus views, observed for silhouette stimuli in psychophysical experiments. Also the model reproduces the processing of shaded stimuli, and a new perceptual illusion, which illustrates a lighting-from-above prior in the processing of biological motion stimuli.

Structure of shading pathway

Figure 1: Architecture of shading pathway. After initial filter stage modelling V1 simple cells by gabor filters the strong gradients of the outer contour are suppressed. Internal gradients are analyzed with appropriate filters and pooled, producing input tot Gaussian radial basis funcion usints that have been trained with example patterns of shaded walkers. 

 

Model stages

Figure 2: Responses of internal gradient detectors in the  model to walker silhouettes with different internal shading gradients. (Arrow lenbgth corresponds to the response amplitude of internal gradient detectors.)

Publications

Fedorov, L., Dijkstra, T. & Giese, M. A. (2018). Lighting-from-above prior in biological motion perception. Scientific Reports, 8(1), 1507.
Lighting-from-above prior in biological motion perception
Authors: Leonid Fedorov Tjeerd Dijkstra Martin A. Giese
Research Areas: Uncategorized
Type of Publication: Article
Journal: Scientific Reports
Volume: 8
Number: 1
Pages: 1507
Year: 2018
Fedorov, L., Chang, D., Giese, M. A., B\"ulthoff, H. & de la Rosa, S. (2018). Adaptation aftereffects reveal representations for encoding of contingent social actions. PNAS, 115(29), 7515-7520.
Adaptation aftereffects reveal representations for encoding of contingent social actions
Abstract:

A hallmark of human social behavior is the effortless ability to relate one’s own actions to that of the interaction partner, e.g., when stretching out one’s arms to catch a tripping child. What are the behavioral properties of the neural substrates that support this indispensable human skill? Here we examined the processes underlying the ability to relate actions to each other, namely the recognition of spatiotemporal contingencies between actions (e.g., a “giving” that is followed by a “taking”). We used a behavioral adaptation paradigm to examine the response properties of perceptual mechanisms at a behavioral level. In contrast to the common view that action-sensitive units are primarily selective for one action (i.e., primary action, e.g., ‘throwing”), we demonstrate that these processes also exhibit sensitivity to a matching contingent action (e.g., “catching”). Control experiments demonstrate that the sensitivity of action recognition processes to contingent actions cannot be explained by lower-level visual features or amodal semantic adaptation. Moreover, we show that action recognition processes are sensitive only to contingent actions, but not to noncontingent actions, demonstrating their selective sensitivity to contingent actions. Our findings show the selective coding mechanism for action contingencies by action-sensitive processes and demonstrate how the representations of individual actions in social interactions can be linked in a unified representation

Authors: LA Fedorov DS Chang Martin A. Giese; HH B\"ulthoff S de la Rosa
Type of Publication: Article
Fedorov, L., Vangeneugden, J. & Giese, M. A. (2016). Neural Model for the Influence of Shading on the Multistability of the Perception of Body Motion. BEST PAPER AWARD, In Proceedings of the 8th International Joint Conference on Computational Intelligence, Portugal 2016, 3, 69-76.
Neural Model for the Influence of Shading on the Multistability of the Perception of Body Motion
Authors: Leonid Fedorov Joris Vangeneugden Martin A. Giese
Research Areas: Uncategorized
Type of Publication: Article
Giese, M. A., Fedorov, L. & Vogels, R (2015). Interaction between adaptation and perceptual multi-stability in body motion recognition Abstract submitted for VSS 2015, 15-20 Mai, Florida. Journal of Vision, Vol.15, 557.
Interaction between adaptation and perceptual multi-stability in body motion recognition
Authors: Martin A. Giese; Leonid Fedorov Rufin Vogels
Research Areas: Uncategorized
Type of Publication: In Collection
Publisher: Journal of Vision, Vol.15, 557

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