Comprised of chapters by leaders in research on connexins, the structural and functional properties of gap junctions, and the roles of electrical synapses in the mammalian brain, this text introduces novel ideas about the functions of gap junctions. Topics covered include molecular biology, structure, diversity, regulation, and distribution of connexins in the brain, as well as the importance of gap junctions for glial regulation of brain metabolism and roles of electrical synapses in specific circuits of the central nervous system. The authors explain the purpose and implementation of various methods of investigation and emphasize the theoretical implications of their work.