Synapses, the specialized junctions between neurons through which chemical messages flow, may not be the only places where nerve cells communicate. Based on electron microscope images of a chick embryo synapse, Terrence J. Sejnowski of the Salk Institute for Biological Studies in La Jolla, Calif., and his colleagues developed a three-dimensional computer model detailed down to nine nanometers. The investigators simulated the release of messenger chemicals and neurotransmitters within the synapse and compared their data with recordings from living cells. The data from the real neurons and the model matched only when the model released a whopping 90 percent of the neurochemicals outside the synapse. These emissions seem to almost always only activate receptors similarly lying outside the synapse, suggesting hitherto unknown channels of communication that may be more important than synapse-to-synapse chatter. The findings appear in the July 15 Science.