Deciphering the circuitry of the neocortex requires knowledge of its components, making a systematic classification of neocortical neurons necessary. GABAergic interneurons contribute most of the morphological, electrophysiological and molecular diversity of the cortex, yet interneuron subtypes are still not well defined. To quantitatively identify classes of interneurons, 59 GFP-positive interneurons from a somatostatin-positive mouse line were characterized by whole-cell recordings and anatomical reconstructions. For each neuron, we measured a series of physiological and morphological variables and analyzed these data using unsupervised classification methods. PCA and cluster analysis of morphological variables revealed three groups of cells: one comprised of Martinotti cells, and two other groups of interneurons with short asymmetric axons targeting layers 2/3 and bending medially. PCA and cluster analysis of electrophysiological variables also revealed the existence of these three groups of neurons, particularly with respect to action potential time course. These different morphological and electrophysiological characteristics could make each of these three interneuron subtypes particularly suited for a different function within the cortical circuit.
Keywords: GABA, cluster, Martinotti, neurolucida, PCA
Citation: McGarry LM, Packer AM, Fino E, Nikolenko V, Sippy T and Yuste R (2010) Quantitative classification of somatostatin-positive neocortical interneurons identifies three interneuron subtypes. Front. Neural Circuits 4:12. doi: 10.3389/fncir.2010.00012
Received: 18 December 2009;
Paper pending published: 09 January 2010;
Accepted: 29 March 2010; Published online: 14 May 2010
Edited by:Gábor Tamás, University of Szeged, Hungary
Reviewed by:Alejandro F. Schinder, Leloir Institute, Argentina
Copyright: © 2010 McGarry, Packer, Fino, Nikolenko, Sippy and Yuste. This is an open-access article subject to an exclusive license agreement between the authors and the Frontiers Research Foundation, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are credited.
*Correspondence: Laura M. McGarry, Department of Biological Sciences, Columbia University, 1212 Amsterdam Avenue, Box 2435, New York, NY 10027, USA. e-mail: firstname.lastname@example.org.