Estimation of thresholds for evoked potentials using a laboratory computer.
To study drug effects on bioelectric activity evoked by near-threshold stimulation, we have developed a computerized threshold estimation technique. The procedure utilizes a laboratory computer (PDP 11/34) equipped with a standard laboratory interface with A/D and D/A capabilities. Program-controlled voltage pulses, delivered via D/A, are interfaced through a constant current stimulus isolation unit for electrical stimulation. One channel of activity is digitized at a user-defined rate and the signal is searched for a response. Responses were generally defined by a feature of the signal which was greater than a multiple of its standard deviation in the subthreshold signal. Using some a priori knowledge of the expected response and user-defined processing options, the program determines threshold on-line without pretrial test data. Program operation is illustrated with sensory evoked potentials in acutely prepared cats and hippocampal evoked potentials in chronically implanted rats.
D000818:Animals; D002415:Cats; D003201:Computers; D004558:Electric Stimulation; D005073:Evoked Potentials, Somatosensory; D005074:Evoked Potentials, Visual; D006624:Hippocampus / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D009482:Neurophysiology / Q000295:instrumentation*; D009897:Optic Chiasm / Q000502:physiology*; D011826:Radial Nerve / Q000502:physiology; D012684:Sensory Thresholds; D012984:Software; D013003:Somatosensory Cortex / Q000502:physiology*; D009435:Synaptic Transmission