Multisite Spike-Field Coherence, Theta Rhythmicity, and Information Flow Within Papezs Circuit

Understanding the temporal and spectral structure of neural coding with especial attention to regional specificity and behavioral function is one goal of system neuroscience. Several methodological approaches have been used to analyze signals arising from multisite or distributed probes placed in distant areas to study synchrony and interaction in various species. Neuronal synchronization may be a way to enhance neuronal interactions among neural ensembles but the exact nature of this process remains largely unknown. Spike-field coherence has recently become a popular method when functional integration analysis is being considered for simultaneously collected hybrid signals, such as local field potentials and spike trains. In this chapter, we review some of the most recent approaches and applications of this methodology to address neural circuitry function and behavioral significance. Many authors have contributed extensively to our current understanding of synchronous signals in relation to neural interaction but far more is to occur in future years when both data acquisition and analysis techniques continue to expand. One intriguing and fascinating process to address using these techniques is undoubtedly the hippocampal theta rhythm. Its relevance to brain information processing and behavior makes it both an excellent target process to understand neural states in relation to behavioral significance and a source of physiologically complex integrative signal as many brainstem, diencephalic, and cortical structures appear to contribute to its generation and maintenance. At the end of this chapter, we discuss our own work on neuronal synchronization and resonance within three structures of Papez’s circuit namely, hippocampus, anterior thalamus, and retrosplenial cortex, and discuss its importance for mnemonic function.