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Focused Review ARTICLE

Many specialists for suppressing cortical excitation

Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, MO, USA

Cortical computations are critically dependent on GABA-releasing neurons for dynamically balancing excitation with inhibition that is proportional to the overall level of activity. Although it is widely accepted that there are multiple types of interneurons, defining their identities based on qualitative descriptions of morphological, molecular and physiological features has failed to produce a universally accepted ÃƒÂ¢Ã‚Â€Ã‚Â˜parts listÃƒÂ¢Ã‚Â€Ã‚Â™, which is needed to understand the roles that interneurons play in cortical processing. A list of features has been published by the Petilla Interneurons Nomenclature Group, which represents an important step toward an unbiased classification of interneurons. To this end some essential features have recently been studied quantitatively and their association was examined using multidimensional cluster analyses. These studies revealed at least 3 distinct electrophysiological, 6 morphological and 15 molecular phenotypes. This is a conservative estimate of the number of interneuron types, which almost certainly will be revised as more quantitative studies will be performed and similarities will be defined objectively. It is clear that interneurons are organized with physiological attributes representing the most general, molecular characteristics the most detailed and morphological features occupying the middle ground. By themselves, none of these features are sufficient to define classes of interneurons. The challenge will be to determine which features belong together and how cell type-specific feature combinations are genetically specified.

Keywords:

cerebral cortex, interneurons, GABAergic neurons, inhibition

Citation:

Burkhalter A (2008). Many specialists for suppressing cortical excitation. Front. Neurosci. 2:2. doi: 10.3389/neuro.01.026.2008

Received:

06 July 2008;

Paper pending published:

18 September 2008;

Accepted:

18 September 2008;

Published online:

15 December 2008.

Edited by:

Javier DeFelipe, Cajal Institute (CSIC), Spain

Reviewed by:

Kathleen S. Rockland, RIKEN Brain Science Institute, Japan
Patrick R. Hof, Mount Sinai School of Medicine, USA

© 2008 Burkhalter. 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:

Andreas Burkhalter, Department of Anatomy and Neurobiology, 8108, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO, 63110, USA. burkhala@pcg.wustl.edu