Introduction to QtracW Threshold Tracking Software
QtracW Threshold Tracking Software is a flexible, stimulus-response data acquisition program with averaging, threshold-tracking and latency-tracking facilities, originally written for studies of human nerves in vivo, but also used for microneurography, muscle excitability testing and cortical excitability testing with transcranial magnetic stimulation. It is most appropriate for experiments in which the excitability or response of the preparation varies slowly with time, either due to programmed changes in the stimulus or to an externally initiated treatment, and the data of primary interest are the changes in selected parameters (threshold, amplitude, latency, etc.) of the response with time. All or selected raw response waveforms can also be recorded, enabling the time course of additional response parameters to be calculated after the recording is finished. QTrac (which became QtracW when adapted for Windows) comprises separate stimulation and plotting programs, QTracS and QTracP, both written in Visual Basic 6.0, which have the same mode of operation and share many of the same facilities.
The Digitimer DS5 Bipolar Constant Current Stimulator was specifically designed to work with QtracW software for human studies of nerve excitability. The major components of a human nerve excitability setup include a PC running QtracW software, a nerve stimulator (e.g. Digitimer DS5), an isolated EMG amplifier (e.g. Digitimer D440-2) and a compatible DAQ interface. We also strongly recommend the Quest Scientific Humbug Noise Eliminator or Digitimer D400-2/D400-4 to remove mains interference, as many QtracW systems are mobile and used in electrically noisy hospital environments. For animal-based studies, our DS4 Biphasic Stimulator is compatible with QtracW.
For those unfamiliar with the application of QtracW software in studies of nerve excitability, we recommend the recent article by Prof. Matthew Kiernan and colleagues (Kiernan et al. 2020), which provides guidelines for the measurement of axonal excitability and provides a state of the art review of axonal excitability research.