Parvalbumin interneurons and oscillations enhance information processing in cortical microcircuits

Abstract

Event Abstract Back to Event Parvalbumin interneurons and oscillations enhance information processing in cortical microcircuits Oscillations in fast-spiking neurons that express parvalbumin may be involved in information processing, and may be deficient in neural circuit pathologies including schizophrenia. However, it has not been possible to demonstrate a quantitative impact of this oscillatory system on information processing. Here we use dynamic clamp and optogenetic tools to deconstruct the pyramidal cell- parvalbumin interneuron microcircuit, and information theory to measure how oscillations affect the function of each circuit element. First, we studied how oscillations affect single neocortical pyramidal neurons. Using dynamic clamp, we stimulated neocortical pyramidal neurons with trains of simulated excitatory post-synaptic currents (sEPSCs). During each train, the rate of sEPSCs varied, and in some cases, we additionally modulated the sEPSC rate at theta (8 Hz) or gamma (40 Hz) frequencies. Theta frequency modulation increased mutual information between the output spike rate of pyramidal neurons and the number of input sEPSCs from 1.13 ±0.08 to 1.39 ± 0.06 bits per 125-msec cycle (p<0.001; n = 14 cells). Similarly, gamma oscillations increased the sEPSC-spike rate information from 0.42 ±0.05 to 0.63 ±0.05 bits per 25-msec cycle (p<0.001; n = 14 cells). Theta, but not gamma, frequency oscillations also increased the information carried by the time of the first spike in each cycle (p<0.001; n = 14 cells). To extend this approach to microcircuits, we used light to activate layer V pyramidal neurons expressing channelrhodopsin (ChR2). We varied the rate of light flashes, and again modulated the rate at theta or gamma frequencies. We recorded from both pyramidal neurons directly activated by light (n = 13), and downstream neurons, using the fast-spiking phenotype to identify parvalbumin interneurons (n = 7). Both theta and gamma frequency modulation markedly increased mutual information between the output spike rate of post-synaptic fast-spiking interneurons and the rate of spikes in pre-synaptic pyramidal neurons. Theta oscillations increased the information / 125 msec cycle from 0.92 ±0.09 bits to 1.12 ±0.09 bits (p<0.05), whereas gamma oscillations increased information / 25 msec cycle from 0.36 ±0.05 bits to 0.71 ±0.07 bits (p<0.001). These increases resulted from decreased noise entropy in fast-spiking interneurons, and were specific to fast-spiking interneurons, as oscillations did not enhance information transmitted from pyramidal neurons to other types of post-synaptic neurons. Finally, to complete the pyramidal neuron - parvalbumin interneuron loop, we activated parvalbumin interneurons, and measured their effects on information processing. In mice selectively expressing ChR2 in parvalbumin interneurons, we stimulated pyramidal neurons with sEPSC trains, and used pyramidal neuron spikes to trigger light flashes and recruit feedback inhibition from parvalbumin interneurons. Such inhibition generated emergent gamma oscillations in pyramidal neurons, and also increased the efficiency of rate coding, measured by the mutual information per spike. These results demonstrate and quantify a powerful synergy between fast-spiking parvalbumin interneurons and oscillations: parvalbumin interneurons generate emergent gamma oscillations, which amplify incoming signals into pyramidal neurons, and increase the fidelity with which these signals are transmitted to parvalbumin interneurons. Conference: Computational and systems neuroscience 2009, Salt Lake City, UT, United States, 26 Feb - 3 Mar, 2009. Presentation Type: Oral Presentation Topic: Oral Presentations Citation: (2009). Parvalbumin interneurons and oscillations enhance information processing in cortical microcircuits. Front. Syst. Neurosci. Conference Abstract: Computational and systems neuroscience 2009. doi: 10.3389/conf.neuro.06.2009.03.089 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 02 Feb 2009; Published Online: 02 Feb 2009. Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Google Google Scholar PubMed Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.