He later showed, using brain imaging techniques, that the same principles apply to the organisation of the human visual brain. In recent work he has shown that parallel processing appears to extend beyond the mere processing of visual signals to their grouping in parietal cortex. His work on colour vision was influenced by the work and methods of Edwin H. Land, whose techniques he employed in his physiological and brain imaging experiments, and which led him to the view that colour is constructed by the brain and that a specialised visual area, area V4, is critical to this process.