Decision letter | An inhibitory corticostriatal pathway

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An inhibitory corticostriatal pathway

Decision letter

Affiliation details

University of Texas at San Antonio, United States
Sacha B Nelson, Reviewing editor, Brandeis University, United States

In the interests of transparency, eLife includes the editorial decision letter and accompanying author responses. A lightly edited version of the letter sent to the authors after peer review is shown, indicating the most substantive concerns; minor comments are not usually included.

Thank you for submitting your article "An inhibitory corticostriatal pathway" for consideration by eLife. Your article has been favorably evaluated by Gary Westbrook (Senior editor) and three reviewers, one of whom, Sacha Nelson, is a member of our Board of Reviewing Editors.

The following individuals involved in review of your submission have agreed to reveal their identity: Charles Gerfen, Mitsuko Watabe-Uchida (peer reviewers).

The reviewers have discussed the reviews with one another and the Reviewing Editor has drafted this decision to help you prepare a revised submission.

Summary:

The study by Apicella and colleagues characterizes an important recently identified inhibitory cortico-striatal pathway to striatal spiny projection neurons. The significance of this finding cannot be overstated as for over 30 years the assumption has been that cortical input to the striatum is exclusively excitatory. A few partial descriptions have previously indicated an inhibitory component to this project. Here the authors use modern state of the art optogenetic techniques to characterize the nature and physiological impact of this projection.

Essential revisions:

1) The authors should provide better documentation of the neuroanatomy in Figure 1. The main finding in this paper concerns SOM cortical neuron projections to the striatum. The one low magnification of the labeling in the striatum is inadequate, both a low and high magnification image of the distribution of the fibers in the striatum would be nice. Also, the low level images of the retrograde labeling of SOM neurons in the cortex should be added to with higher magnification images that allow one to get a sense of the numbers and laminar distribution of these neurons. It would also be nice if the authors were able to provide a Neurolucida drawing of an axon from one of the cortical neurons going into the striatum (although it is recognized this might be difficult).

2) The rigorous characterization of SOM neurons projecting from layer 5 and 6 of cortex to striatal D1 and D2 MSNs in this paper will be important for the field. However, because the existence of GABAergic projections from the cortex to the striatum, and the fact that some of them were SOM neurons (and PV neurons), have already been reported anatomically and physiologically, it is very important to show what proportion of these GABAergic projections are from SOM neurons and what proportion of MSNs in the striatum receive these projections.

3) The text (Introduction, Results, and Discussion) should more thoroughly discuss past studies of corticostriatal GABAergic projections. For example, are the present physiological results consistent with previous ones in the ventral striatum or different? "A class of GABAergic neurons in the PFC sends long-range projections to NAc and elicits acute avoidance behavior" By Lee et al. in J. Neuroscience 2014 (the most related, including electrophysiology), "Corticofugal GABAergic projection neurons in the mouse frontal cortex" by Tomioka et al. in Frontiers in Neuroanatomy 2015 (mapping of cortical GABAergic projection sites and identification as somatostatin neurons), and "Parvalbumin is expressed in glutamatergic and GABAergic corticostrial pathway in mice." by Jinno and Kosaka in J. Comp. Neurol. 2004 (probably original finding about GABA projection from cortex to striatum). Authors cited them briefly and improperly in the second paragraph of the Introduction and in the first paragraph of the Discussion.

[Editors' note: further revisions were requested prior to acceptance, as described below.]

Thank you for submitting your article "An inhibitory corticostriatal pathway" for consideration by eLife. Your article has been favorably evaluated by Gary Westbrook (Senior editor) and three reviewers, one of whom, Sacha B Nelson, is a member of our Board of Reviewing Editors.

The following individuals involved in review of your submission have agreed to reveal their identity: Charles R Gerfen (Reviewer #2); Mitsuko Watabe-Uchida (Reviewer #3).

Although the reviewers felt that most of the points raised were addressed, they did not feel that the slightly higher magnification view of the same image added much to Figure 1 and encourage you to provide an additional image (either as part of Figure 1 or as a supplementary figure) that actually shows greater detail as to the distribution of axons and cell bodies. We will not hold up acceptance of the manuscript on this point if you are unable to provide an additional image in a relatively short period, but all three reviewers felt this would be a significant improvement to the manuscript with relatively little additional effort.

An additional thing that needs to be corrected is the last sentence of the Abstract, "previously unknown" should be deleted as this pathway had been described before.

DOI: http://dx.doi.org/10.7554/eLife.15890.008