Figure 1.

Addressing the neural basis of behavior requires defining the behavioral processes to be understood in terms of the underlying algorithms and computations (left). The implementations can then be probed by recording and manipulating activity in targeted neural circuits during behavior. Typical intermediate goals are: first, to identify the elements in the brain ‘essential’ for a given process (red squares – ‘the causal network’), second, to describe the functions of the different parts, and third, to elucidate the logic by which these functions are implemented. The ultimate goal is to account for the behavioral ‘process’ in terms of how the various ‘parts’ (neurons and brain areas) interact, and to extract general rules that govern these interactions. This review discusses how different types of circuit manipulations can help us achieve this grander goal, and some of their pitfalls.