In order to assess perfusion and metabolic responses in relation to neural function, the cellular signaling network, including the types of neurons and astrocytes involved, and the timing of their activation need to be known/specified. Here, we present the basis for measuring brain activity and metabolism in rats and mice, which covers basic electrophysiological indicators of neuronal function, a short description of the methods commonly used for recording electrophysiological signals, examples of data analysis, and a brief look at the limitations of the methods. This chapter describes animal preparation, the origin of extracellularly recorded electrical signals, with special regard to the EEG, local field potentials, and spikes (action potentials?) in rodent preparations. We also describe methods for recording cerebral blood flow (CBF), tissue partial pressure of oxygen (tpO₂), and cytosolic calcium transients. Lastly, we give examples of protocols in which electrophysiology, blood flow, cerebral rate of oxygen metabolism (CMRO2), and calcium transients have been studied together.