Neurophysiological data supports two models for the disparity selectivity of binocular simple and complex cells in primary visual cortex. These involve binocular combinations of monocular receptive fields that are shifted in retinal position (the position-shift model) or in phase (the phase-shift model) between the two eyes. This article presents a formal description and analysis of a binocular energy model with these forms of disparity selectivity. We propose how one might measure the relative contributions of phase- and position-shifts in simple and complex cells. The analysis also reveals ambiguities in disparity encoding that are inherent in these model neurons, suggesting a need for a second stage of processing. We propose that linear pooling the binocular responses across orientations and scales (spatial frequency) is capable of producing an unambiguous representation of disparity. 1 Introduction Neurons sensitive to binocular disparity have been found in the visual cortex of ma...

... This article presents one alternative to the computer metaphor suggesting that brains are organized into independent modules. Evidence is reviewed that brains are organized into parallel processing streams with complementary properties. Hierarchical interactions within each stream and parallel interactions between streams create coherent behavioral representations that overcome the complementary deficiencies of each stream and support unitary conscious experiences. This perspective suggests how brain design reflects the organization of the physical world with which brains interact. Examples from perception, learning, cognition, and action are described, and theoretical concepts and mechanisms by which complementarity is accomplished are presented.

Many models for stereo disparity computation have been proposed, but few can be said to be truly biological. There is also a rich literature devoted to physiological studies of stereopsis. Cells sensitive to binocular disparity have been found in the visual cortex, but it is not clear whether these cells could be used to compute disparity maps from stereograms. Here we propose a model for biological stereo vision based on known receptive field profiles of binocular cells in the visual cortex and provide the first demonstration that these cells could effectively solve random dot stereograms. Our model also allows a natural integration of stereo vision and motion detection. This may help explain the existence of units tuned to both disparity and motion in the visual cortex. 1 Introduction It is well known that binocular disparity forms the basis of stereoscopic depth perception. There have been many physiological investigations on the mechanisms of stereopsis (see Freeman and Ohzawa, 19...

We previously proposed a physiologically realistic model for stereo vision based on the quantitative binocular receptive field profiles mapped by Freeman and coworkers. Here we present several new results about the model that shed light on the physiological processes involved in disparity computation. First, we show that our model can be extended to a much more general class of receptive field profiles than the commonly used Gabor functions. Second, we demonstrate that there is, however, an advantage of using the Gabor filters: Similar to our perception, the stereo algorithm with the Gabor filters has a small bias towards zero disparity. Third, we prove that the complex cells as described by Freeman et al. compute disparity by effectively summing up two related cross products between the band-pass filtered left and right retinal image patches. This operation is related to cross-correlation but it overcomes some major problems with the standard correlator. Fourth, we demonstrate that as...

Phase-based methods for extracting binocular disparity are discussed, including phase-difference methods and phase-correlation. A third method is also described that combines some of their properties, and appears consistent with recent physiological data. 1 Introduction This paper outlines a method for extracting binocular disparity. It borrows from two existing approaches, namely, phase-difference methods [15, 5, 2, 16], and phase-correlation methods [8, 4, 13], and was designed to be consistent with recent physiological data [12]. We begin with a review of phase-difference and phase-correlation methods. They are both shown to be instances of the same basic approach, differing in the form of band-pass filters, stability constraints, and the control strategy, where phase-correlation looks more like a voting scheme than a coarse-to-fine approach. From this perspective, noting the advantages and disadvantages of both methods, we outline a new model that combines desirable properties of...

Non-Fourier motion is now commonplace in research on visual motion perception, yet lacks a computational framework. This paper examines this issue based on the observation that many non-Fourier motion stimuli have a simple characterization in the frequency domain, in terms of oriented power distributions that lie along lines (or planes) that do not pass through the origin. This provides a unifying theoretical framework for a very diverse class of non-Fourier phenomena. It also allows us to examine some central issues concerning the computational nature of non-Fourier models, and naturally occurring sources of non-Fourier motion. For example, it is shown that the orientation of power in frequency domain corresponds to the velocity of a multiplicative envelope, and may arise as a restricted form of lighting effects, translucency or occlusion. We also show that both the location and orientation of spectral power may be extracted from the phase and amplitude output of band-pass filters, co...

: 274, Introduction: 676, Discussion: 2402 Acknowledgments. Thanks to Ken Miller, Allan Dobbins, Christof Koch, and the anonymous reviewers for many helpful comments on this work. This work was funded by the National Science Foundation and the Office of Naval Research, and by a Sloan Foundation Fellowship (D.R.). Abstract Hubel and Wiesel (1962) first distinguished "simple" from "complex" cells in visual cortex, and proposed a processing hierarchy in which rows of LGN cells are pooled to drive oriented simple cell subunits, which are pooled in turn to drive complex cells. Though parsimonious and highly influential, the pure hierarchical model has since been challenged by results indicating many complex cells receive excitatory monosynaptic input from LGN cells, or do not depend on simple cell input. Alternative accounts for complex cell orientation tuning remain scant, however, and the function of monosynaptic LGN contacts onto complex cell dendrites remains unknown. We have used a ...

A key goal of behavioral and cognitive neuroscience is to link brain mechanisms to behavioral functions. The present article describes recent progress towards explaining how the visual cortex sees. Visual cortex, like many parts of perceptual and cognitive neocortex, is organized into six main layers of cells, as well as characteristic sub-lamina. Here it is proposed how these layered circuits help to realize processes of development, learning, perceptual grouping, attention, and 3D vision through a combination of bottom-up, horizontal, and top-down interactions. A key theme is that the mechanisms which enable development and learning to occur in a stable way imply properties of adult behavior. These results thus begin to unify three fields: infant cortical development, adult cortical neurophysiology and anatomy, and adult visual perception. The identified cortical mechanisms promise to generalize to explain how other perceptual and cognitive processes work.

It is well established that multiple stimulus dimensions (e.g., orientation and spatial frequency) are mapped onto the surface of striate cortex. However, the detailed organization of neurons within a local region of striate cortex remains unclear. Within a vertical column, do all neurons have the same response selectivities? And if not, how do they most commonly differ and why? To address these questions, we recorded from nearby pairs of simple cells and made detailed spatiotemporal maps of their receptive fields. From these maps, we extracted and analyzed a variety of response metrics. Our results provide new insights into the local organization of striate cortex. First, we show that nearby neurons seldom have very similar receptive fields, when these fields are characterized in space and time. Thus, there may be less redundancy within a column than previously thought. Moreover, we show that correlated discharge in-Columnar organization is a common feature of cortical architecture (Mountcastle, 1997). Neurons along a path perpendicular to the cortical surface often have similar functional properties, and these properties often vary systematically across the surface of the cortex. In primary visual (or striate) cortex, systems of columns are well documented for orientation preference, ocular dominance, and retinotopic location (Hubel and Wiesel, 1977). Preferred spatial frequency also has an orderly representation, although the details of this organization remain controversial (Maffei and Fiorentini, 1977; Tootell et al., 1981; Berardi et al.,

A laminar cortical model of stereopsis and 3D surface perception is developed and simulated. The model describes how monocular and binocular oriented filtering interact with later stages of 3D boundary formation and surface filling-in in the LGN and cortical areas V1, V2, and V4. It proposes how interactions between layers 4, 3B, and 2/3 in V1 and V2 contribute to stereopsis, and how binocular and monocular information combine to form 3D boundary and surface representations. The model includes two main new developments: (1) It clarifies how surface-toboundary feedback from V2 thin stripes to pale stripes helps to explain data about stereopsis. This feedback has previously been used to explain data about 3D figure-ground perception. (2) It proposes that the binocular false match problem is subsumed under the Gestalt grouping problem. In particular, the disparity filter, which helps to solve the correspondence problem by eliminating false matches, is realized using inhibitory interneurons as part of the perceptual grouping process by horizontal connections in layer 2/3 of cortical area V2. The enhanced model explains all the psychophysical data previously simulated by Grossberg and Howe (2003), such as contrast variations of dichoptic masking and the correspondence problem, the effect of interocular contrast differences on stereoacuity, Panum's limiting case, the Venetian blind