Signal-to-Noise Ratio (SNR)

Signal-to-noise ratio (SNR) is the ratio of the amplitude of your neural signal to the amplitude of background noise. It's the most important metric for recording quality and determines what signals you can reliably detect.

Why it matters: Higher SNR means clearer signals, better spike isolation, and more confident detection of neural events. Poor SNR makes spike sorting difficult or impossible and obscures subtle neural signals.

Calculating SNR: For spikes: SNR = peak spike amplitude / RMS noise amplitude Good recordings: SNR > 3-4 (spike amplitude 3-4× noise level) Excellent recordings: SNR > 5-6

Sources of noise:

• Thermal noise: From electrode impedance (Johnson noise)
• Amplifier noise: Electronic components in recording system
• Biological noise: Synaptic activity, distant neurons, EMG
• Environmental noise: 60 Hz line noise, electromagnetic interference

Improving SNR: Use appropriate site size for signal type, ensure good electrical shielding, maintain proper grounding, use differential amplification, keep amplifiers close to recording sites, consider electrode coating to reduce impedance.