Isabelline (colour) form of leucism caused by a uniform reduction in the production and expression of melanin resulting in areas of plumage on the back of the bird, normally black, being strongly faded, or isabelline, in appearance. Isabellinism has been reported in several species of penguin. Isabelline and isabella are terms applied in Europe to very pale palomino or cremello horses, animals with a coat colour that is variously described as cream, pale gold or almost white; this is the primary usage of the French ("isabelle") and German ("Isabella") versions of the word. In horses, this colour is created by the action
Colour centre colour centre begins in V1 and sends signals to extrastriate areas V2 and V4 for further processing. V4 in particular is an area of interest because of the strength of the colour receptive fields in its neurons. V4 was initially identified in macaque monkey visual cortex experiments. Originally, it was proposed that colour was selectively processed in V4. However, this hypothesis was later rejected in favour of another hypothesis which suggested that V4 and other areas around V4 work together to process colour in the form of multiple colour selective regions. After identification of V4 as the colour-selective region in