Collaborating Pis and Consultant United States Pl: Anitha Pasupathy, Dept. of Biological Structure, University of Washington, Seattle, USA Co-Pl: Wyeth Bair, Dept. of Biological Structure, University of Washington, Seattle, USA Japan Pl: lsamu Motoyoshi, Dept. of Life Sciences, The University of Tokyo, Japan Consultant: Hidehiko Komatsu, Tamagawa University, Japan Specific Aims Our visual system endows us with a diverse set of abilities: to recognize and manipulate objects, avoid obstacles and danger during navigation, evaluate the quality of food, read text, interpret facial expressions, etc. This relies on the neuronal processing of information about form and material texture along the ventral pathway of the primate visual system (Ungerleider & Mishkin, 1982; Felleman & Van Essen, 1991). Studies over the past several decades have produced detailed models of how visual information is processed in V1, the earliest stage along . this pathway (Hubel & Wiesel, 1959, 1968; Movshon et al., 1978a, b; Albrecht et al., 1980), but beyond V1 our understanding of visual processing and representation is limited. This is particularly true with regard to our understanding of how visual representations of form and texture jointly contribute to object perception and recognition. The broad goal of this proposal is two-fold-to develop an experimentally-driven image-computable model for how naturalistic visual stimuli are processed in area V4, an important intermediate stage along the ventral visual pathway (Aim 1) and to discover how such a representation contributes to perception (Aim 2). Past studies have shown that V4 neurons are sensitive to both the form (Desimone and Schein, 1987; Kobatake and Tanaka, 1994; Gallant et al., 1993; Pasupathy and Connor, 2001; Nandy et al., 2013) and the surface texture of visual stimuli (Arcizet et al., 2008; Goda et al., 2014; Okazawa et al., 2015). But, because expertise is narrow and experimental time limited, scientists tend to focus exclusively on the encoding of form or texture and not on their joint coding. For example, in the laboratories of the USA portion of this collaboration, we have until now focused on form processing by carrying out neurophysiological studies using 2D shapes with uniform surface properties to investigate how object boundaries are encoded (Oleskiw et al., 2014; Popovkina et al., 2016). We have modeled our data by comparing the representation of V4 neurons to that of the units in AlexNet (Pospisil et al., 2015), a prominent convolutional neural net (CNN) trained to recognize objects (Krizhevsky et al., 2012). At the same time, the Japanese contingent of this collaboration has investigated the encoding of surface texture and gloss in human perception without associated form encoding (Motoyoshi et al., 2007; Sharan et al., 2008; Motoyoshi, 2010; Motoyoshi & Matoba, 2012). Here we propose to bring our respective expertise in studying form and texture encoding to bear on the question of how naturalistic stimuli with both form and surface cues are encoded in area V4 and how these representations support human visual perception.
Our specific aims are:
Aim1. To build a unified image-computable model for neuronal responses to shapes and textures in area V4 V4 responses to 2D shapes with uniform luminance/chromatic characteristics can be explained by a hierarchical-Max (HMax) model for object recognition that emphasizes boundary features (Cadieu et al., 2007). Such responses can also be explained by units in artificial deep convolutional networks, in which boundary features are not explicitly emphasized (all features are learned from initially random weights). On the other hand, V4 responses to texture patches can be well explained by a higher-order image-statistics-based model (Okazawa et al., 2015). Using shape data from the Pasupathy lab and texture data from the Komatsu lab (Japanese consultant), we will ask whether responses of V4 neurons to shapes and textures can be Page 21