Hue tuning curves in V4 change with visual context

Abstract

To understand activity in the visual cortex, researchers typically investigate how parametric changes in stimuli affect neural activity. A fundamental tenet of this approach is that the response properties of neurons in one context, e.g. color stimuli, are representative of responses in other contexts, e.g. natural scenes. This assumption is not often tested. Here, for neurons in macaque area V4, we first estimated tuning curves for hue by presenting artificial stimuli of varying hue, and then tested whether these would correlate with hue tuning curves estimated from responses to natural images. 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 color-responsive. One explanation of this result is that neurons in V4 respond to interactions between hue and other visual features. This finding exemplifies how tuning curves estimated by varying a small number of stimulus features can communicate a small and potentially unrepresentative slice of the neural response function.