Example traces of in vivo extracellular electrophysiology recordings from anesthetized P7, P14, and adult mice. Top traces are 10 seconds of recordings, middle traces are 1 second of recording, and bottom traces are examples of simple spikes (left) and complex spikes (right) from each different age. Complex spikes are indicated with an asterisk (*). During development, Purkinje cells start to fire more frequently and more regularly with less pauses between simple spike trains.