Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 2006.Includes bibliographical references.Introduction: This thesis contains two main projects that I worked on during my graduate studies at MIT. Both address the subject matter of how neurons communicate, process, and pass information within the context of larger neuronal ensembles. The first project focuses on information transfer between two neurons during synaptic transmission. The project was spurred by an initial observation that neuronal communication through synapses in young and developing neuronal networks is only "half-hearted" in that signals propagate predominantly through only one type of synaptic receptor (the NMDA receptor), and bypass the principal signaling pathway present in mature synaptic transmission (AMPA receptor) (Malenka and Nicoll 1997). The possible cause of this abnormality was either that AMPA receptors were lacking on the postsynaptic side, or that something else in the process of synaptic transmission rendered them inoperable.by Boris Krupa.Ph.D.