The patterns of activity of neurons are produced by connections between neurons that form the circuits that drive behavior. By doing electrical recording from identified pairs of neurons we can reveal the patterns of connections and reconstruct the circuit diagram of a network for a particular behavior.
Simultaneous electrical recordings from an inhibitory neuron (gycinergic cell) and a neuron called the Mauthner cell at the top show that activating the inhibitory neuron leads to an inhibitory response in the Mauthner cell. This indicates that the glycinergic cell acts to suppress activity in the Mauthner cell. Bottom: Following the electrical recording, the recorded neurons were filled with green (glycinergic cell) and red (Mauthner cell) dyes and reconstructed in 3D to show their relationships. The blue cells are all of the glycinergic neurons in the brain.