Optimal sampling of electrophysiological signals

Action potentials (APs) and field potentials (FPs) are commonly used to study functions of the brain. To facilitate their analysis, computer methods are often used. The high‐speed nature of APs and the large amount of data of FPs put stringent requirements on the sampling rate used. To determine optimal sampling rates for these signals a modified sampling equation is derived. This equation formulates the relationship among the order of the anti‐aliasing filter, the sampling rate, and the number of bits of quantization. For convenience, a table is also provided to reveal the optimal sampling rate for various combinations of filters and analog‐to‐digital converter cards commonly available. The recordings of compound action potentials, APs, and FPs were practically used to further examine this relationship. Under the specified conditions for the recording of these electrophysiological signals, their highest frequency contents are about 10 kHz, 9.3 kHz and 40 Hz, respectively. In conclusion, this paper provides a tutorial, quick reference, and step‐by‐step guide to sample a signal faithfully; that is, free from the contamination of aliasing errors no matter the spectrum of the signal is known. Also, the role of necessity of a high order anti‐aliasing filter is emphasized.