title: Task context impacts visual object processing differentially across the cortex.
abstract: Perception reflects an integration of "bottom-up" (sensory-driven) and "top-down" (internally generated) signals. Although models of visual processing often emphasize the central role of feed-forward hierarchical processing, less is known about the impact of top-down signals on complex visual representations. Here, we investigated whether and how the observer's goals modulate object processing across the cortex. We examined responses elicited by a diverse set of objects under six distinct tasks, focusing on either physical (e.g., color) or conceptual properties (e.g., man-made). Critically, the same stimuli were presented in all tasks, allowing us to investigate how task impacts the neural representations of identical visual input. We found that task has an extensive and differential impact on object processing across the cortex. First, we found task-dependent representations in the ventral temporal and prefrontal cortex. In particular, although object identity could be decoded from the multivoxel response within task, there was a significant reduction in decoding across tasks. In contrast, the early visual cortex evidenced equivalent decoding within and across tasks, indicating task-independent representations. Second, task information was pervasive and present from the earliest stages of object processing. However, although the responses of the ventral temporal, prefrontal, and parietal cortex enabled decoding of both the type of task (physical/conceptual) and the specific task (e.g., color), the early visual cortex was not sensitive to type of task and could only be used to decode individual physical tasks. Thus, object processing is highly influenced by the behavioral goal of the observer, highlighting how top-down signals constrain and inform the formation of visual representations.
authors.affiliation: Laboratory of Brain and Cognition, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892.
authors.forename: Assaf
authors.initials: A
authors.lastname: Harel
authors.forename: Dwight J
authors.initials: DJ
authors.lastname: Kravitz
authors.forename: Chris I
authors.initials: CI
authors.lastname: Baker
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008960:Models, Psychological; D009483:Neuropsychological Tests; D010775:Photic Stimulation; D017397:Prefrontal Cortex / Q000502:physiology*; D021641:Recognition, Psychology / Q000502:physiology*; D014793:Visual Cortex / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*
keywords: fMRI; object recognition; occipitotemporal cortex; top-down processing; vision