Network Experimental Approaches: Ex vivo Recording

The cellular and molecular mechanisms supporting cognitive and autonomic homeostases can be effectively investigated in ex vivo preparations (e.g. acute brain sections) where they are disconnected from the behavioral context and where parameters that define physiological processes can be manipulated and optimized. Therefore, ex vivo preparations allow modeling of pathophysiological conditions and delineation of the properties and performance of functionally defined neuronal circuits. However, replacing a functional brain with brain sections may limit the interpretation and physiological relevance of results because surgical manipulations damage brain tissues, while the artificial cerebrospinal fluid only approximately emulates the native physiological milieu (see Chapter 10). This chapter reasons that a compromise between the benefits and limitations of ex vivo preparations can be achieved to provide insights into network mechanisms that are not adequately addressed by in vivo (e.g. freely moving or anesthetized animals) or in vitro (e.g. cultured cells and cell lines) experimental approaches. Three distinct mechanisms (i.e. direct synchronization, inhibition of asynchrony, and enhancement of neuronal excitability) that enhance the impact of individual neurons on the network function are discussed using experimental data obtained from the olfactory, hippocampal, and hypothalamic acute brain preparations.