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Posted by pbio on 07 May 2009 at 22:29 GMT

Author: Ju Lu
Position: Postdoctoral Fellow
Institution: Jeff Lichtman Lab, Department of Molecular and Cellular Biology and Center for Brain Science, Harvard University
Additional Authors: Jeff W. Lichtman
Submitted Date: February 16, 2009
Published Date: February 23, 2009
This comment was originally posted as a “Reader Response” on the publication date indicated above. All Reader Responses are now available as comments.

Although there is no generally accepted definition of "connectome," we would like to use the term to mean something slightly different from neural circuit." In our opinion, "connectome" refers to the complete wiring diagram at the cellular level of a particular instantiation of a neural circuit (either the entire nervous system or a subnetwork of it). We provided an argument on how completeness distinguishes the connectomic approach from conventional circuit analysis using sparse labeling, pair-wise recording, data-pooling from multiple samples and a probabilistic interpretation of the data.

It seems to us that the anatomical and physiological information about the STG network has been obtained primarily through conventional approaches and the circuit diagrams (e.g., Fig. 1b in Nusbaum & Beenhakker 2002) are "generic" rather than specific to one individual animal. However, as Marder and colleagues have shown, there is substantial variability in membrane currents and mRNA expression levels (Schulz et al. 2006), as well as neuronal morphology (Bucher et al. 2007) among the neurons of the same identifiable type in STG. These results suggest that at the single cell and synaptic level, there may be substantial differences in the wiring diagrams from animal to animal. Thus the full wiring diagram, or connectome, would have to be "individualized" to each specific animal to reveal whether such variability exists. To our knowledge, no such connectome has been obtained yet.


Bucher D, Johnson CD, Marder E. (2007) “Neuronal morphology and neuropil structure in the stomatogastric ganglion of the lobster, Homarus americanus.” J. Comp. Neurol. 501(2):185-205.

Nusbaum MP, Beenhakker MP. (2002) “A small-systems approach to motor pattern generation.” Nature. 417:343-350.

Schulz DJ, Goaillard JM, Marder E. (2006) “Variable channel expression in identified single and electrically coupled neurons in different animals.” Nat. Neurosci. 9(3):356-62.

No competing interests declared.