Sector light Authorities). For example, the United States uses a signalling stereotype which is the opposite of Europe. In USA, the red light indicates the starboard side of the channel for harbour bound vessels, while the green light indicates the port side of the same channel. An expression to remind of this is "red right returning". An example of a sector light is the light of the Fisgard Lighthouse in British Columbia. The lighthouse as built to guide ships through the entrance of Esquimalt harbour. The white sector is an isophase light of 2s from 322° to 195°. If the ship sees
Colour centre the recognition of shapes, motion, and colour. V1 has multiple areas that are colour-sensitive, which indicates that colour processing is not limited to one area. According to a paper by Dr Robert Shapley, V1 has an important role in colour perception. fMRI experimental results showed that V1 has two kinds of colour sensitive neurons: single-opponent and double-opponent cells. These cells are integral in the opponent process of interpreting colour signals. Single-opponent neurons respond to large areas of colour. This is advantageous for recognizing large colour scenes and atmospheres. In comparison, double opponent cells respond to patterns, textures, and colour boundaries.