Over the last five decades, progress in neural recording techniques has allowed the number of simultaneously recorded neurons to double approximately every 7 years, mimicking Moore’s law. Following Stevenson and Kording (2011), this site aims to keep track of these advances in electrophysiology. If you notice a missing data point email me with a reference and the number of neurons recorded.
For an excellent review of early simultaneous recording see Kruger, 1983. Kruger traces the earliest simultaneous recording to Matthews, 1929 from the frog peroneal nerve. Here we include observations after ~1950 when multi-electrode recording began.