What is the signal-to-noise ratio of a spike recording, and where does its noise come from? · Lobeworks/17

The size of a spike compared with everything else on the trace: a 50 µV spike over about 6 µV of noise, as on Neuropixels, is a ratio near 8 and easy to detect, while the same spike under 50 µV would be lost.

What is the signal-to-noise ratio of a spike recording, and where does its noise come from?

The size of a spike compared with everything else on the trace: a 50 µV spike over about 6 µV of noise, as on Neuropixels, is a ratio near 8 and easy to detect, while the same spike under 50 µV would be lost. The noise comes from the thermal agitation of charges in the electrode and the amplifier, the transistors themselves, interference from mains and equipment, movement, and the spikes of all the other neurons. Amplification never improves the ratio, so it is set by the first stage, next to the electrode.