Supriya Balaji Ramachandran1, Kevin D Gillis2. 1. Department of Bioengineering, 254 Agricultural Engineering, Columbia, MO, USA; Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA. 2. Department of Bioengineering, 254 Agricultural Engineering, Columbia, MO, USA; Department of Medical Pharmacology and Physiology, 1 Hospital Dr., Columbia, MO, USA; Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA. Electronic address: GillisK@missouri.edu.
Abstract
BACKGROUND: Electrochemical microelectrodes located immediately adjacent to the cell surface can detect spikes of amperometric current during exocytosis as the transmitter released from a single vesicle is oxidized on the electrode surface. Automated techniques to detect spikes are needed in order to quantify the spike rate as a measure of the rate of exocytosis. NEW METHOD: We have developed a Matched Filter (MF) detection algorithm that scans the data set with a library of prototype spike templates while performing a least-squares fit to determine the amplitude and standard error. The ratio of the fit amplitude to the standard error constitutes a criterion score that is assigned for each time point and for each template. A spike is detected when the criterion score exceeds a threshold and the highest-scoring template and the time of peak score is identified. The search for the next spike commences only after the score falls below a second, lower threshold to reduce false positives. The approach was extended to detect spikes with double-exponential decays with the sum of two templates. RESULTS: Receiver Operating Characteristic plots (ROCs) demonstrate that the algorithm detects >95% of manually identified spikes with a false-positive rate of ∼2%. COMPARISON WITH EXISTING METHODS: ROCs demonstrate that the MF algorithm performs better than algorithms that detect spikes based on a derivative-threshold approach. CONCLUSIONS: The MF approach performs well and leads into approaches to identify spike parameters.
BACKGROUND: Electrochemical microelectrodes located immediately adjacent to the cell surface can detect spikes of amperometric current during exocytosis as the transmitter released from a single vesicle is oxidized on the electrode surface. Automated techniques to detect spikes are needed in order to quantify the spike rate as a measure of the rate of exocytosis. NEW METHOD: We have developed a Matched Filter (MF) detection algorithm that scans the data set with a library of prototype spike templates while performing a least-squares fit to determine the amplitude and standard error. The ratio of the fit amplitude to the standard error constitutes a criterion score that is assigned for each time point and for each template. A spike is detected when the criterion score exceeds a threshold and the highest-scoring template and the time of peak score is identified. The search for the next spike commences only after the score falls below a second, lower threshold to reduce false positives. The approach was extended to detect spikes with double-exponential decays with the sum of two templates. RESULTS: Receiver Operating Characteristic plots (ROCs) demonstrate that the algorithm detects >95% of manually identified spikes with a false-positive rate of ∼2%. COMPARISON WITH EXISTING METHODS: ROCs demonstrate that the MF algorithm performs better than algorithms that detect spikes based on a derivative-threshold approach. CONCLUSIONS: The MF approach performs well and leads into approaches to identify spike parameters.
Authors: R M Wightman; J A Jankowski; R T Kennedy; K T Kawagoe; T J Schroeder; D J Leszczyszyn; J A Near; E J Diliberto; O H Viveros Journal: Proc Natl Acad Sci U S A Date: 1991-12-01 Impact factor: 11.205