Telemetry system for recording neural activities in pigs-Comparison with cable system

We recently developed a telemetry system for recording neural activity in the brains of unrestrained pigs. To test the fidelity of waveform reproduction, we compared local field potentials in the temporal hippocampus of six pigs by simultaneous recording with a cable system. We analyzed differences between the telemetry and cabled data filtered through a low-cut filter at 1, 4, or 30 Hz. Analysis of 10,000 data recorded while pigs were lying down showed a higher correlation with low-cut filtering at 4 or 30 Hz than at 1 Hz. Over 97% of differences in amplitude between the telemetry and cable data lay within the 95% confidence interval. Measurements were reproducible. A box plot of the differences clearly showed increased data symmetry and reduced skewness by low-cut filtering at 4 or 30 Hz. Almost the same results were obtained in two animals during feeding. Thus, the local field potentials in the temporal hippocampus were telemetered with almost the same accuracy as by cable measurement during both resting and feeding. However, artifacts in the first 100 ms (low-cut filtering at 1 or 4 Hz) or 5 ms (30 Hz) of measurements had to be removed for analysis.