John M
It is an old adage in physiology that structure reflects function. In the brain-stem reticular activating system (RAS) there reside three nests of cells making peculiar chemicals known as the biogenic amines, viz. noradrenaline, dopamine and 5-hydroxytryptamine (5HT). What is more, the ramifications of these cells are distributed over the whole extent of the cerebral cortex. What is their function?
English 
Spanish 
Chinese 
Russian 
German 
French 
Japanese 
Portuguese 
Hindi