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1_how_to_review_your_peer_s_essay

INSTRUCTIONS

To provide an example of peer-editing, below is a student submission that has been edited by the instructor and scored using the grading rubric.

---------------------------------------------------------------------------------------------------------------------------- FIRST WE PRESENT THE ORIGINAL STUDENT SUBMISSION

Immortality is an alluring concept. Some scientists believe that it will be possible to "upload" one's mind by recreating the circuitry of the brain in silico. Before we can upload brains, we first must reverse-engineer neural circuitry and begin by creating a circuit map.

Electron microscopy provides the only possible method through which we're able to clearly visualize synapses and follow neural processes. Volumetric reconstruction of neural tissue using electron microscopic resolution is necessary to map neural circuitry. Focused ion-beam scanning electron microscopy (Knott et al. 2008) gives excellent quality images, but fails to process tissue pieces larger than 40 microns in diameter. Thin sections imaged with transmission electron microscopy succumb to the damaging effects of manual handling and section distortion. Thus, it's most prudent to use a method that images the block-face directly and is capable of imaging large block-faces. Serial block-face scanning electron microscopy (SBEM; Denk and Horstmann 2004) provides both necessary components.

Using SBEM, Dr. Kevin Briggman and associates (Briggman, Helmstaedter, and Denk 2011) recently mapped the connections between starburst amacrine cells and bipolar ganglion cells in the mouse retina to better understand the wiring specificity, elucidating the cellular circuit between starburst amacrine cells and direction-selective bipolar retinal ganglion cells.

By staining a 200-micron piece of retina, which contained the entire arborization field of a starburst amacrine cell with an extracellular stain that could outline cells and neural processes in SBEM, Briggman was then able to reconstruct neural processes. Based on morphology, he assessed the locations and sizes of putative synapses on these processes.

Unfortunately, synapses were invisible within the data because the tissue was only stained with an extracellular, electron-dense stain and some synaptic features are intracellular. In an effort to address this ambiguity, Briggman then stained a second piece of tissue where synapse-associated features were

stained and visible. He then correlated the extracellular morphology found at synapses between the first and second pieces of tissue.

This is the first example of relatively large neural circuit reconstruction and it solved controversy about exactly how starburst amacrine cells are wired to be directionally-selective. The next steps in whole-brain circuit reconstruction will be large sample preparation (Mikula, Binding, and Denk 2012) and imaging on a whole-brain SBEM for mapping the whole mouse brain as a first mammalian complete connectome (Seung 2011).

References

Knott, Graham,et al. ―Serial Section Scanning Electron Microscopy of Adult Brain Tissue Using Focused Ion Beam Milling.‖ The Journal of Neuroscience 28, no. 12 (March 19, 2008): 2959–2964.

Denk, Winfried, and Heinz Horstmann. ―Serial Block-Face Scanning Electron Microscopy to Reconstruct Three-Dimensional Tissue Nanostructure.‖ PLoS Biology 2, no. 11 (November 2004).

Briggman, Kevin L., Moritz Helmstaedter, and Winfried Denk. ―Wiring Specificity in the Direction-selectivity Circ uit of the Retina.‖ Nature 471, no. 7337 (March 10, 2011): 183–188.

Mikula, Shawn, Jonas Binding, and Winfried Denk. ―Staining and Embedding the Whole Mouse Brain for Electron Microscopy.‖ Nature Methods In press (2012).

Seung, H. Sebastian. ―Neuroscience:Towards Functional Connectomics.‖ Nature 471, no. 7337 (March 10, 2011): 170–172.

SECOND WE PRESENT THE REVIEWD STUDENT SUBMISSION

----------------------------------------------------------------------------------------------------------------------------INSTRUCTOR SCORES ON RUBRIC

?Clarity: 2/3

?Concision: 2/3

?Style: 2/3

?Organization: 3/3

?Focus: 3/3

?Total: 12/15

---------------------------------------------------------------------------------------------------------------------------- REVIEWING LEGEND

This is an insertion.This is a deletion.[This is a comment.]

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INSTRUCTOR EDITS

In the first example of a relatively large neural circuit reconstruction, Dr. Kevin Briggman and colleagues (Briggman, Helmstaedter, and Denk 2011) recently mapped the connections between key neurons—starburst amacrine cells and bipolar ganglion cells—in the mouse retina. The work solves a long-standing controversy about exactly how starburst amacrine cells are wired to be directionally-selective [can you say this more plainly?].

Electron microscopy provides the only possible method through which we're able to clearly Briggman's team used serial block-face electron microscopy (SBEM; Denk and Horstmann 2004) to visualize synapses and follow neural processes. Volumetric reconstruction of neural tissue using e E lectron microscopic resolution is necessary to map neural circuitry. Focused ion-beam scanning electron microscopy (Knott et al. 2008) gives excellent quality images, but fails to process tissue pieces larger than 40 microns in diameter;. Thin sections imaged with and transmission electron microscopy requires ultra-thin samples that often succumb to the damaging effects of manual handling and section distortion. Thus, it's most prudent to use a method that images the block-face directly and is capable of imaging

large block-faces. Serial block-face scanning electron microscopy (SBEM; Denk and Horstmann 2004) provides both necessary components.

Briggman's team treated By staining a 200-micron piece of retina, which contained including the entire arborization field of a starburst amacrine cell with an extracellular stain that could outline cells and neural processes in SBEM, Briggman was then able to reconstruct neural processes. Due to their many intracellular features, Briggman's team could not directly visualize synapses. But, B b ased on morphology, t he y assessed inferred the locations and sizes of putative synapses on these processes. They also Unfortunately, synapses were invisible within the data because the tissue was only stained with an extracellular, electron-dense stain and some synaptic features are intracellular. In an effort to address this ambiguity, Briggman then stained a second piece of tissue where synapse-associated features were stained and visible with an intracellular stain that revealed synapse-associated features,. He then and correlated the extracellular morphology found at synapse s maps between the first and second pieces of tissue.

ADD: PARAGRAPH ABOUT THE CONTROVERSY THAT THEY SOLVED!

This is the first example of relatively large neural circuit reconstruction and it solved controversy about exactly how starburst amacrine cells are wired to be directionally-selective. The next steps in whole-brain circuit reconstruction will be to prepare, image, and map large sample preparation (Mikula, Binding, and Denk 2012) and imaging on a whole mouse -brain. This would represent the SBEM for mapping the whole mouse brain as a first mammalian complete connectome (Seung 2011) and would be the closest anyone has ever come to immortalizing a mammalian brain.

References:

Knott, Graham,et al. ―Serial Section Scanning Electron Microscopy of Adult Brain Tissue Using Focused Ion Beam Milling.‖ The Journal of Neuroscience 28, no. 12 (March 19, 2008): 2959–2964.

Denk, Winfried, and Heinz Horstmann. ―Serial Block-Face Scanning Electron Microscopy to Reconstruct Three-Dimensional Tissue Nanostructure.‖ PLoS Biology 2, no. 11 (November 2004).

Briggman, Kevin L., Moritz Helmstaedter, and Winfried Denk. ―Wiring Specificity in the Direction-selectivity Circuit of the Retina.‖ Nature 471, no. 7337 (March 10, 2011): 183–188.

Mikula, Shawn, Jonas Binding, and Winfried Denk. ―Staining and Embedding the Whole Mouse Brain for Electron Microscopy.‖ Nature Methods In press (2012).

Seung, H. Sebastian. ―Neuroscience: Towards Functional Connectomics.‖ Nature 471, no. 7337 (March 10, 2011): 170–172.