In our endless battle to decode the functioning of all neural circuits in the brain, we have to be able to prove that a neuron or population of neurons causes a response. For many years, neuroscientists were able to associate neural circuits with response patterns, but determining causation remained elusive. With our burgeoning understanding of genetics came the invention of a new research technique designed to tease out these relationships.
Chemogenetics allows scientists to manipulate neural activity in living animals through the application of a chemical (Poth et al., 2021). This is done through an easily repeatable process. A model animal, such as a rat, is genetically engineered to express Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) on the membranous surfaces of specific neuron populations (Smith et al., 2016). A DREADD can be designed to cause a neuron to fire or silence a neuron, whenever the designer drug binds to it. In this way, a researcher can administer the drug and cause firing of this whole population (Lee et al, 2014; Roth, 2016).
Chemogenetics has been especially useful in examining how neural firing patterns translate to behavior (Campbell & Marchant, 2018). It is through the examination of animal behavior that we gain insight into the way in which our own brain’s circuitry comes together to create the wide array of emotions, behaviors, and cognitions.