STCells within nP display low detection thresholds that are comparable to behavior.

<p>(a) Relevant anatomy diagram showing the main brain areas considered. Recordings were made from individual STCells. (b) Top: Stimulus waveform (blue) and its envelope (red) showing contrast as a function of time. Middle: Spiking activity from a representative STCell. The insets show magnification at two time points. In both cases, the STCell activity strongly phase locked to the stimulus, but the average number of spikes per stimulus cycle increased with contrast, similar to that observed for PCells under control conditions. Bottom: Double y-axis plot showing the mean firing rate (solid orange) and VS (dashed orange) of this STCell as a function of time. The band delimits the upper range of values determined from this STCell’s firing rate in the absence of stimulation. Because STCells tended to not fire action potentials in the absence of stimulation, it was not possible to compute a threshold level for the VS. The VS detection threshold (upper black circle) was thus set to the lowest contrast for which the STCell reliably fired action potentials for at least 5 consecutive stimulus cycles (see <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.2005239#sec015" target="_blank">Materials and methods</a>). Inset: The population-averaged detection thresholds obtained from firing rate (left) and VS (middle) were not significantly different from one another or from behavior (Kruskal-Wallis, df = 2; Firing Rate–VS: <i>p</i> = 0.51; Firing Rate–Behavior: <i>p</i> = 0.06; VS-Behavior: <i>p</i> = 0.99). The data can be downloaded at <a href="https://figshare.com/s/93707200732db87bb80f" target="_blank">https://figshare.com/s/93707200732db87bb80f</a>. EA, electrosensory afferent; ELL, electrosensory lateral line lobe; EODf, electric organ discharge frequency; nP, nucleus praeeminentialis; PCell, pyramidal cell; STCell, stellate cell; VS, vector strength.