Organization of Neuropil

ganglia in the nerves in coded form, as a spatial-temporal pattern of all-or-none im? pulses. Decoding of the incoming message and recoding of the appropriate outgoing response occur somewhere in the ganglia. Many of the fundamental problems of neurophysiology revolve around the related questions of the functional significance of impulse patterns in the central ganglia (codes), and of the mechanisms of central neural integration (coding and decoding). Information about impulse patterns and the properties of integrative systems can be derived from input-output analyses (Wiers? ma, 1962), but problems regarding detailed mechanism eventually require penetration into the ganglion and dissection of the integrating system itself. Let us look, then, at the organization of a central invertebrate ganglion. The em? phasis will be on arthropod material, for I am most familiar with this group; most of the comments should apply with little modification to many of the annelids, mol? luscs, and lower vertebrates.