A computer-controlled system for post-stimulus time histogram and wind-up studies

Abstract

A LabVIEW 2 virtual instrument (VI)-based system is described for stimulation of sensory fibers in peripheral nerves and analysis and storage of electrophysiological data recorded from the spinal cord. The system utilizes a commercially available multifunction data acquisition (input/output; I/O) board, graphical programming environment and custom built VIs. Electrical stimuli are triggered by the I/O board and delivered at C-fiber strength to the receptive field of a multireceptive dorsal horn neuron. The stimulus frequency can be chosen between 0.1 and 1 Hz. Extracellular action potentials are recorded with a compound recording/iontophoresis carbon-fiber microelectrode and sampled by the I/O board. Post-stimulus time histograms (PSTH) are computed to visualize the preferred times of neuronal firing evoked by A- and C-fiber inputs. Responses of the neuron to repetitive stimulation are analyzed by their latency relative to the stimulus and plotted against the stimulus number. Wind-up, the progressive potentiation of C fiber-evoked response per stimulus, is increased by NMDA and decreased by MK-801 when each is applied by microiontophoresis. The system is well suited to perform combined PSTH and wind-up analysis on-line as well as to examine previously recorded data off-line. Principles of operation and diagrams of greater importance are explained in detail. To illustrate system operation, sample recordings, PSTH and wind-up analyses from a dorsal horn neuron are presented. The software is available from the author.