Object representations in human ventral and dorsal cortex depend on display format and physical distance.

Abstract

Physical distance and real-world size are important visual cues for object perception and action. Yet most studies of vision rely on pictorial stimuli that are not relevant for action, and whose distance and size are ambiguous. We used functional MRI to explore how the human brain represents object information when the stimuli are real objects versus two-dimensional pictures, and when the stimuli appear at different physical distances from the observer. Although stimulus distance had powerful effects on functional MRI response amplitudes for both formats, proximity amplified responses to real objects more than responses to pictures in areas such as lateral occipital and parietal cortex. Distance also had a powerful effect on functional MRI response patterns. While response patterns were generally similar for both formats, distance had different effects on representations in the ventral and dorsal processing pathways. In ventral cortex, object characteristics such as physical size were evident in the representations irrespective of stimulus proximity; however, in dorsal cortex, such characteristics were only evident for proximal stimuli. Our results reveal fundamental similarities and differences in how object information is represented in ventral and dorsal cortex when the stimuli convey characteristics that are relevant for both perception and action.