Stereo viewing modulates three-dimensional shape processing during object recognition: A high-density ERP study
Journal of Experimental Psychology: Human Perception and Performance
The role of stereo disparity in the recognition of 3-dimensional (3D) object shape remains an unresolved issue for theoretical models of the human visual system. We examined this issue using high-density (128 channel) recordings of event-related potentials (ERPs). A recognition memory task was used in which observers were trained to recognize a subset of complex, multipart, 3D novel objects under conditions of either (bi-) monocular or stereo viewing. In a subsequent test phase they
... d previously trained targets from untrained distractor objects that shared either local parts, 3D spatial configuration, or neither dimension, across both previously seen and novel viewpoints. The behavioral data showed a stereo advantage for target recognition at untrained viewpoints. ERPs showed early differential amplitude modulations to shape similarity defined by local part structure and global 3D spatial configuration. This occurred initially during an N1 component around 145-190 ms poststimulus onset, and then subsequently during an N2/P3 component around 260 -385 ms poststimulus onset. For mono viewing, amplitude modulation during the N1 was greatest between targets and distracters with different local parts for trained views only. For stereo viewing, amplitude modulation during the N2/P3 was greatest between targets and distracters with different global 3D spatial configurations and generalized across trained and untrained views. The results show that image classification is modulated by stereo information about the local part, and global 3D spatial configuration of object shape. The findings challenge current theoretical models that do not attribute functional significance to stereo input during the computation of 3D object shape. Public Significance Statement The aim of this research is to elucidate how the human visual system processes sensory information about shapes of 3-dimensional (3D) objects so that we can perceive, and recognize, them. We asked whether these processes are sensitive to both monocular and stereo visual input. To answer this question we measured electrophysiological responses generated in the brain while people viewed, and made recognition judgments about, mono or stereo images of 3D objects. The objects could differ from each in terms of their part structure, or overall 3D spatial configuration. The results showed that the visual system processes these sorts of shape properties differently, and that how it does so is influenced differently by mono and stereo visual input. The findings shed new light on the role of stereo information in the visual perception and recognition of 3D object shape.