Kreiman, Gabriel and Krahe, Rudiger and Metzner, Walter and Koch, Christof and Gabbiani, Fabrizio (2000) Robustness and Variability of Neuronal Coding by Amplitude-Sensitive Afferents in the Weakly Electric Fish Eigenmannia. Journal of Neurophysiology, 84 (1). pp. 189-204. ISSN 0022-3077. http://resolver.caltech.edu/CaltechAUTHORS:20130816-103210812
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We investigated the variability of P-receptor afferent spike trains in the weakly electric fish, Eigenmannia, to repeated presentations of random electric field AMs (RAMs) and quantified its impact on the encoding of time-varying stimuli. A new measure of spike timing jitter was developed using the notion of spike train distances recently introduced by Victor and Purpura. This measure of variability is widely applicable to neuronal responses, irrespective of the type of stimuli used (deterministic vs. random) or the reliability of the recorded spike trains. In our data, the mean spike count and its variance measured in short time windows were poorly correlated with the reliability of P-receptor afferent spike trains, implying that such measures provide unreliable indices of trial-to-trial variability. P-receptor afferent spike trains were considerably less variable than those of Poisson model neurons. The average timing jitter of spikes lay within 1–2 cycles of the electric organ discharge (EOD). At low, but not at high firing rates, the timing jitter was dependent on the cutoff frequency of the stimulus and, to a lesser extent, on its contrast. When spikes were artificially manipulated to increase jitter, information conveyed by P-receptor afferents was degraded only for average jitters considerably larger than those observed experimentally. This suggests that the intrinsic variability of single spike trains lies outside of the range where it might degrade the information conveyed, yet still allows for improvement in coding by averaging across multiple afferent fibers. Our results were summarized in a phenomenological model of P-receptor afferents, incorporating both their linear transfer properties and the variability of their spike trains. This model complements an earlier one proposed by Nelson et al. for P-receptor afferents of Apteronotus. Because of their relatively high precision with respect to the EOD cycle frequency, P-receptor afferent spike trains possess the temporal resolution necessary to support coincidence detection operations at the next stage in the amplitude-coding pathway.
|Additional Information:||Copyright © 2000 The American Physiological Society. Received 10 November 1999; accepted in final form 21 March 2000. The authors thank Dr. M. Stopfer for carefully reading the manuscript and suggesting many improvements. Experiments were carried out by R. Krahe and W. Metzner. Data analysis was carried out by G. Kreiman and F. Gabbiani. F. Gabbiani and G. Kreiman co-wrote the paper. The original experiments were designed by F. Gabbiani, C. Koch, and W. Metzner. This work was supported by a National Science Foundation grant to C. Koch and W. Metzner, by a National Institute of Mental Health grant to C. Koch, and by the Sloan Center for Theoretical Neuroscience.|
|Group:||Koch Laboratory, KLAB|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||KLAB Import|
|Deposited On:||11 Jan 2008 20:11|
|Last Modified:||19 Nov 2015 00:41|
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