grammaticality - Especially + verb + Subject

I have just found the following sentence:

Especially is this true in the field of psychology.

I know the rule that says that whenever a sentence begins with an adverb that expresses negativity, it should come first the verb and then the subject. However, in this case, it does not seem to be the case for a subject-verb inversion.

Can anyone explain the grammatical reason why this sentence is correct? Does this inversion have to do with the adverb especially?

Answer

It's formally known as "Intro Adverbial" inversion. The "limiting" adverb goes to the front as an introductory to the sentence. Consider:

Never had I met someone so interesting.
Not often will he go to work

Look up the uses of inversion. One of them is emphasis.

Especially is this true in the field of psychology.

This is an example of inversion for emphasis. Especially is brought forward using inversion so as to highlight its significance in the context. Saying "This is true" is simple; "This is especially true" adds significance but still has the focus on true; "Especially is this true" shifts the emphasis to especially, which is an adverb limiting the scope of the verb.