Electrophysiology: From molecule to cognition, from animal to human

Electrophysiology is the field of study that examines physiological signals of the brain. It ranges from assessment of molecular activity using patch clamp techniques to population measurements such as electroencephalography (EEG). This chapter deals with those methods and their role in drug discovery. The on-cell patch is the most widely used patch clamp technique, which measures the activity of one ion in a community of intracellular ions. Single-cell recordings are done to assess changes in action potentials, the output of a system. Intracranial electrodes can also be used to detect activity from multiple or populations of neurons. Depending on how the signal is filtered, indirect action potentials (i.e., output from a region) or postsynaptic signals (i.e., input to a region) are detected. A final type of measurement described in this chapter is EEG. The measured signal, obtained from the scalp, is similar to that obtained from local field potentials that are recorded intracranially. EEG measured in humans has frequently been compared to local field potentials recorded from living animals, showing a number of similarities between species. However, due to genetic or anatomical differences, in combination with differing electrode locations, it is still unclear how comparable the signals are. Future research should try to optimize animal methodology to increase the translational potential.