Construction of a simple spike counter for analysis of electrophysiological recording data

A method for constructing a simple spike counter from a conventional calculator by taking advantage of the "adding display to memory" function [(M+) key] is described. The modification involves connecting the (M+) key to a dissecting pin and to a metallic notebook binder which is taped on to a transparent plastic sheet. The plastic sheet can then be placed on top of a polygraph record. After entering "1" into the calculator, a spike can be counted by making a single contact between the pin and the metal fastener. The total number of spikes counted can be displayed on the calculator by pressing the key for memory recall. The spike counter described herein is suitable for counting extracellular action potentials recorded on chart paper as well as other biological signals such as the rate of contraction of muscle.