I have a bunch of files in a directory where the modification time was changed (incorrectly) with `touch -m`

The access time of these files is still close enough to what the modification time was, so I'd like to change them back.

Is there a way of doing a `touch` where it sets the mtime = atime? I don't want to set them all to the same timestamp, but I want to go file-by-file setting mtime = atime.