The revenge of Quine-Duhem

Below is a reference to a recent paper showing specific ways in which (some) data collected using a certain data acquisition system (Plexon) are not trustworthy (from the Journal of Neuroscience Methods). This is significant, as a very large number of labs use Plexon. This could be an interesting case study of the discovery and resolution of problems with measuring devices in neuroscience, a case where if there is a controversial theory based on these data, it could turn out to be the “raw” data that are to blame. This is the kind of thing that can ruin an experimentalist’s day! Pubmed link.

The measuring devices in general in neurophysiology are quite delicate and complicated machines, and unlike our advisors, my generation of physiologists can largely get away with having little idea how they work. We buy a patch clamp system from a company, plug it in, and  it works. This news about the Plexon system is gonna bite some people in the butt (well, in practice the researchers will just reanalyze their data to see if the results still hold once the problem is corrected for).

Nelson MJ, Pouget P, Nilsen EA, Patten CD, Schall JD. (2008) Review of signal distortion through metal microelectrode recording circuits and filters. J Neurosci Methods. 30;169(1):141-57.

Interest in local field potentials (LFPs) and action potential shape has increased markedly. The present work describes distortions of these signals that occur for two reasons. First, the microelectrode recording circuit operates as a voltage divider producing frequency-dependent attenuation and phase shifts when electrode impedance is not negligible relative to amplifier input impedance. Because of the much higher electrode impedance at low frequencies, this occurred over frequency ranges of LFPs measured by neurophysiologists for one head-stage tested. Second, frequency-dependent phase shifts are induced by subsequent filters. Thus, we report these effects and the resulting amplitude envelope delays and distortion of waveforms recorded through a commercial data acquisition system and a range of tungsten microelectrodes. These distortions can be corrected, but must be accounted for when interpreting field potential and spike shape data.