ABSTRACT
In planarians, the CNS forms an inverted U-shape consisting of a cephalic ganglion and several branches. Recent advances in molecular studies using expressed sequence tags (EST) and cDNA microarray techniques allow more detailed studies of the planarian central nervous system (CNS). Planarians express a wide range of CNS-related genes, including those essential for functioning of the brain, showing that there are possibly more than seven functional regions in the cephalic ganglion. Although planarians have an apparendy primitive and simple morphology, they have a well-organized and complex CNS structure.
