You're not generally distributing, performing, &c. your state of mind. On the other hand, if you then go and generate work based on what you read, then distributing that work certainly can be infringing. Thus "clean room" techniques, where one team reads copyrighted text, writes up a spec (which may then be checked off by lawyers), and then another team, without reading the copyrighted text, implements based off the spec, are sometimes used to attempt to launder copyright taint.

Taking a step back, the fact that well-known authors have infamously declared that they don't read fanfiction as a CYA move against accusations of plagiarism suggests that yes, brains that have read text are widely considered derivative.