The Function and Fallibility of Visual Feature Integration: A Dynamic Neural Field Model of Illusory Conjunctions
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1
Institute for Neural Computation, Ruhr-University Bochum, Germany
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2
University of Iowa, Department of Psychology, United States
Objects are composed of various surface features such as color and shape. The visual system codes many of these features in distinct neuronal populations. Yet we normally perceive objects as coherent wholes rather than seeing aggregations of unrelated features. This suggests the existence of an integrative process conjoining visual features. Psychophysical studies indicate this integration process to be fallible, however, as it sometimes erroneously combines features from different objects. These errors are referred to as illusory conjunctions [1]. For example, when subjects briefly view a multi-letter display containing a green ‘T’ and a red ‘X’, they might report having seen a green ‘X’. Illusory conjunctions provide a valuable test case with respect to the functional mode of visual feature integration.
We developed a neurodynamic model of the processes involved in integrating visual features into multi-feature objects, based on the framework of Dynamic Field Theory [2]. We then tested it using a typical illusory conjunctions task. The model consists of several coupled neural field representations with lateral interactions, organized into three modules: First, a low-level representation of the visual stimuli, capturing feature information and location; second, a spatial pathway, dealing with spatial attention and the read out of item location; third, a surface feature pathway, dealing with feature attention. The surface feature pathway additionally includes a feature representation that can either retain feature information of one item in the form of sustained activity or read out an item’s feature information. The model includes two instances of both the low-level representation and the surface feature pathway, one for color and one for shape. The two low-level representations are connected only through the spatial pathway. When information about a feature of one item is retained in the surface feature pathway, it exerts a biasing effect on the other parts of the model. As a consequence, the spatial location of the respective item is selectively attended. As this location also contains the item’s second feature, it can be extracted from the low-level representation. The resulting pattern of activation then fully captures the item’s feature and location configuration. In the process, illusory conjunctions may emerge due to the coarse nature of featural and spatial selection mechanisms.
Our model captures several key findings reported in the behavioral literature. Namely, illusory conjunctions occur more often between spatially close stimuli [3] and between stimuli that share similar features [4]. Additionally, the illusory percept tends to be located at the midpoint between the two involved stimuli [5]. These parallels with psychophysical findings suggest that the model provides a robust theory of feature integration in early vision, particularly supporting the notion of a shared spatial frame as the basis for visual feature integration.
Acknowledgements
The authors acknowledge support from the German Federal Ministry of Education and Research within the National Network Computational Neuroscience - Bernstein Fokus: "Learning behavioral models: From human experiment to technical assistance", grant FKZ 01GQ0951.
References
[1] Treisman, A., & Schmidt, H. (1982). Illusory Conjunctions in the Perception of Objects. Cognitive Psychology, 14(1), 107–141.
[2] Schöner, G. (2008). Dynamical Systems Approaches to Cognition. In R. Sun (Ed.), The Cambridge Handbook of Computational Psychology (pp. 101–126). Cambridge: Cambridge University Press.
[3] Cohen, A., & Ivry, R. (1989). Illusory Conjunctions Inside and Outside the Focus of Attention. Journal of Experimental Psychology. Human Perception and Performance, 15(4), 650–663.
[4] Ivry, R. B., & Prinzmetal, W. (1991). Effect of feature similarity on illusory conjunctions. Perception & Psychophysics, 49(2), 105–116.
[5] Hazeltine, R. E., Prinzmetal, W., & Elliott, W. (1997). If It's Not There, Where Is It? Locating Illusory Conjunctions. Journal of Experimental Psychology. Human Perception and Performance, 23(1), 263–277.
Keywords:
binding,
Feature integration,
illusory conjunctions,
neural field model,
Visual System
Conference:
Bernstein Conference 2012, Munich, Germany, 12 Sep - 14 Sep, 2012.
Presentation Type:
Poster
Topic:
Other
Citation:
Lins
J,
Schneegans
S,
Spencer
J and
Schöner
G
(2012). The Function and Fallibility of Visual Feature Integration: A Dynamic Neural Field Model of Illusory Conjunctions.
Front. Comput. Neurosci.
Conference Abstract:
Bernstein Conference 2012.
doi: 10.3389/conf.fncom.2012.55.00128
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Received:
18 Sep 2012;
Published Online:
12 Sep 2012.
*
Correspondence:
Mr. Jonas Lins, Institute for Neural Computation, Ruhr-University Bochum, Bochum, Germany, Jonas.Lins@ini.rub.de