ABSTRACT
Double-opponent (DO) cells are well-suited to contribute to the spatial processing of color due to their spatially opponent and cone-opponent receptive fields (RFs). However, the representation of visual images by DO cells in monkey primary visual cortex is unclear because the spatial RF structure of DO cells has not been fully characterized. Early reports suggested that DO cells have center-surround RFs, but more recent studies have shown that some DO cells are orientation-tuned. To characterize the RFs of DO cells, we mapped them in awake fixating macaques, fit them with parametric models, and compared them to the benchmark of orientation-tuned simple cells. Neurons were stimulated with colorful, dynamic white noise patterns. Spike-triggered averaging was used to classify each neuron as simple, DO, or neither and to measure its spatial RF. The spatial RF of each neuron was fitted with a Gabor model and a Difference of Gaussians (DoG) model. The Gabor model provided the more accurate description, a result that is incompatible with a center-surround RF organization. The superiority of the Gabor fits was slightly more decisive for simple than for DO cells. A modified (non-concentric) DoG model performed nearly as well as the Gabor model for DO cells.