Hue tuning curves in V4 change with visual context

To understand activity in the higher visual cortex, researchers typically investigate how parametric changes in stimuli affect neural activity. These experiments reveal neurons’ general response properties only when the effect of a parameter in synthetic stimuli is representative of its effect in other visual contexts. However, in higher visual cortex it is rarely verified how well tuning to parameters of simplified experimental stimuli represents tuning to those parameters in complex or naturalistic stimuli. To evaluate precisely how much tuning curves can change with context, we developed a methodology to estimate tuning from neural responses to natural scenes. For neurons in macaque V4, we then estimated tuning curves for hue from both natural scene responses and responses to artificial stimuli of varying hue. We found that neurons’ hue tuning on artificial stimuli was not representative of their hue tuning on natural images, even if the neurons were strongly modulated by hue. These neurons thus respond strongly to interactions between hue and other visual features. We argue that such feature interactions are generally to be expected if the cortex takes an optimal coding strategy. This finding illustrates that tuning curves in higher visual cortex may only be accurate for similar stimuli as shown in the lab, and do not generalize for all neurons to naturalistic and behaviorally relevant stimuli.