A method to measure the strength of multi-unit bursts of action potentials

Both the numbers of neurons that are active during multi-unit bursts of spikes and the frequencies with which individual neurons fire in these bursts can vary in response to changes in excitation. Here is a digital-filtering method that measures the strength of a burst of spikes by calculating the area of a polygon derived from the squared voltages that record the burst, and dividing this area by the burst's duration. The method was developed in the SigmaPlot© environment, and makes use of the Fast-Fourier Transform functions provided in the SigmaPlot© transform language. To test the method's performance, I constructed multi-unit bursts of spikes with known structure and calculated the strengths of these known bursts. To demonstrate the method's usefulness, I applied it to a train of 23 bursts of spikes in motor axons recorded during a spontaneous bout of patterned motor output. The measured strengths of these bursts varied 30-fold, and were well-correlated with the differences in the original recording. The results demonstrate that the method effectively measures burst strength independent of burst duration.