Coordinated Regulation of Inhibitory and Excitatory Local Circuits by Experience During Development of Layer 4 Barrel Cortex

Abstract

Event Abstract Back to Event Coordinated Regulation of Inhibitory and Excitatory Local Circuits by Experience During Development of Layer 4 Barrel Cortex Michael C. Ashby1, Ramesh Chittajallu1 and John T. Isaac1* 1 NINDS, NIH, United States A critical step in the development of primary sensory cortex is maturation of layer 4, which receives a large proportion of ascending thalamic input to neocortex and contains a precise map of the sensory periphery. In rodent barrel cortex, this map is of the facial vibrissae and during the first postnatal week the map is highly sensitive to whisker-driven sensory experience. Neocortical circuits require a close interplay of inhibition and excitation that together produce a transformation of input into appropriate output. In the case of layer 4, the thalamocortical projection is an important input and the excitatory projection neurons, stellate cells, provide the output. We have thus investigated developmental and experience-dependent changes in local inhibitory and excitatory circuits in layer 4 that are driven by thalamic input and assessed effects on stellate cell output. We analyzed inhibitory and excitatory circuits using simultaneous patch-clamp recordings and 2-photon imaging/uncaging of inhibitory interneurons and stellate cells in a thalamocortical slice preparation from mice aged postnatal day 4 – 12, a period when layer 4 is sensitive to sensory experience. We found that feed forward inhibition, driven by thalamic input onto stellate cells, emerges over approximately 2 days at postnatal day (P)8-9 and involves a number of changes in the circuit. Feed forward inhibition when it emerged serves to strongly down regulate stellate cell spiking in response to thalamic input and set dendritic integration. The recruitment of feed forward inhibition requires sensory experience that selectively strengthens the thalamic input onto fast spiking interneurons; other developmental changes in the inhibitory circuit occur independent of whisker experience. Experiments are now currently underway to assess the role of experience in development of feed back inhibition. To investigate development of the recurrent excitatory network in layer 4, we developed a technique using 2-photon glutamate uncaging to map stellate cell to stellate cell connections. In the first postnatal week connectivity was very low (~4 %), but increases threefold over one day at P9, a time that coincides closely with the emergence of feed forward inhibition. Analysis of structural changes in the same cells shows there is a spinogenesis in stellate cells at P9, in which cells progress from having no spines to hundreds of spines in a period of 1 day. Experience drives the threefold increase in functional connectivity, but is not required for the spinogenesis. Current work using 2-photon glutamate uncaging on spines is investigating mechanisms for experience-dependent regulation of spine function. Taken together our analysis of layer 4 circuit development reveals highly coordinated, rapid, experience-dependent changes in inhibitory and excitatory circuits to produce a layer 4 network that can transform input into appropriate output. Conference: EMBO workshop: Gaba Signalling and Brain Networks , Amsterdam, Netherlands, 30 Jun - 2 Jul, 2010. Presentation Type: Oral Presentation Topic: Talks Citation: Ashby MC, Chittajallu R and Isaac JT (2010). Coordinated Regulation of Inhibitory and Excitatory Local Circuits by Experience During Development of Layer 4 Barrel Cortex. Conference Abstract: EMBO workshop: Gaba Signalling and Brain Networks . doi: 10.3389/conf.fnins.2010.15.00041 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: 23 Jun 2010; Published Online: 23 Jun 2010. * Correspondence: John T Isaac, NINDS, NIH, Bethesda, United States, jtrisaac@gmail.com 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 Michael C Ashby Ramesh Chittajallu John T Isaac Google Michael C Ashby Ramesh Chittajallu John T Isaac Google Scholar Michael C Ashby Ramesh Chittajallu John T Isaac PubMed Michael C Ashby Ramesh Chittajallu John T Isaac 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.