Correlations of Cellular Activities in the Nervous System: Physiological and Methodological Considerations

Abstract

Rhythms (cycles, oscillations) and synchronization processes pervade all aspects of the living and nonliving, from circadian rhythms to individual habits and traits (Glass, 2001; Pikovsky et al., 2001). The distributed nature of cognition implies that distinct brain areas must somehow coordinate their activity: cognition, whether in the form of perception or motor actions, results from the integrated spatiotemporal coordinated activity of cell populations in the nervous system, including both glial and neuronal elements. Because the system’s collective behavior is difficult, if not impossible, to deduce from its individual components, the determination of brain-coordinated activity at adequate levels of description becomes fundamental to the understanding of nervous system function and its relation to behavior. Some questions arise: what variables are best suited to measure these correlations in activity? What order parameters should be used to characterize coordinated activity among cellular populations and how do these activity patterns relate to behavioral responses? What level of description should be used? This chapter summarizes some physiological and methodological considerations to aid the science practitioner in the study of correlated activity patterns in nervous systems.