The position and topography of the human colour centre as revealed by functional magnetic resonance imaging

We used a colour Mondrian--an abstract scene with no recognizable objects--and its achromatic version to image the change in blood oxygenation in the brains of 12 human subjects, with the aim of learning more about the position and variability of the colour centre in the human brain. The results showed a consistent association of colour stimulation with activation of an area that is distinct from the primary visual areas, and lies in the ventral occipitotemporal cortex; we refer to it as human V4. The position of human V4, as defined on functional grounds, varies between individuals in absolute terms but is invariably found on the lateral aspect of the collateral sulcus on the fusiform gyrus. There was no indication of lingual gyral activation. In further studies designed to reveal the topographic map within V4, we stimulated the superior and inferior visual fields separately, using the same stimuli. We found that human V4 contains a representation of both the superior and inferior visual fields. In addition, there appears to be retinotopic organization of V4 with the superior visual field being represented more medially on the fusiform gyrus and the inferior field more laterally, the two areas abutting on one another. We find no evidence that suggests the existence of a separate representation of the inferior hemifield for colour in more dorsolateral regions of the occipital lobe.