The dissertation guide says the following about copyright permissions: Before you submit your dissertation electronically, you must have obtained permissions for any copyrighted work included in it for which you do not hold the sole copyright. This may include your own previously published work, whether or not you are its sole author. You may wish to consult your subject librarian or email Olin Library Copyright and Your Dissertation or Thesis: Ownership, Fair Use, and Your Rights and Responsibilities (pdf). 

Let’s translate this statement. First, consider the copyrighted work you’re including. Identify all materials that you might include in the final product, ranging from ordinary quotations to full reproductions of photographs, music, software, and any other copyrightable material. Each item will need at least brief consideration for copyright clearance, but others may require careful evaluation and perhaps even the time to track down a copyright owner for permission. There are two questions you must first ask: 

Is the material image(s) or other works that you found? 

For material that isn’t your own, ask whether copyright expire and therefore the work is in the public domain (or p 11-12). Some works, such as works of the U.S. government, are not protected by copyright. You do not need permission for public domain material. 

Then, ask if the material is under a license that permits your use, such as a Creative Commons license. You might replace material in your dissertation with public domain or openly licensed materials, if necessary, but you do not need permission for openly licensed or Creative Commons-licensed material.

Finally, ask whether your use of the material may be within fair use. Inclusion of images in dissertations is often inherently transformative. Dissertations add original argument and therefore place images in a different context from the original, typically aesthetic, aim of the copyright owner of the image. You do not need permission for something that could reasonably be considered a fair use.

If the material you’re using is not in the public domain, under a license that permits inclusion in your dissertation, or would reasonably be considered fair use, you need to secure permission from the copyright owner. 

Is the material your own previously published work? 

This statement does not mean you need permission from co-authors; however, depending on your publishing agreement, you may need to obtain permission from the publisher. 

Keep These Things in Mind
1. Providing credit or attribution for a copyrighted work is not a substitute for obtaining copyright permission.

2. While permission of co-authors to include shared work in your dissertation is not always needed, there are ethical and other practical reasons why getting permission from co-authors is always best. Likewise, you should get permission from lab PIs before publishing data created in a lab.  

3. Denial of permission does not preclude an assertion of fair use.

4. You as the author retain the copyright to your dissertation. Nothing interferes with your ability to republish your work. 
 

Copyright exists from the moment your work is fixed in a tangible medium of expression, and persists regardless of whether or not you include copyright notice, or register a claim with the U.S. Copyright Office.

Although registration isn't required for protection, it can provide certain benefits. 

Record-keeping function: Registration establishes a public record of the copyright claim, and pins down details about what rights have been claimed. 

Prerequisite for litigation: You cannot file a lawsuit for infringement until your certificate and original work are on file with the Copyright Office. Moreover you cannot claim statutory damages or attorney's fees unless your work was registered before the infringement began. So you can't sue until after registration, and you won't receive much in damages for infringements that occur before you've done so. 

In most cases, it isn't necessary for you to pay ProQuest to register copyright in your dissertation.

Under U.S. Copyright Law and WUSTL IP Policy (§I(3)(b)), student typically retain ownership of intellectual property rights to works they create. As copyright holder, students may decide whether and when their work will be made available beyond the typical course setting. A lot of this comes down to asking about shared expectations.