The Eisenberger team found that emotional pain activates the opposing reactions of these areas activate in exactly the same way.
It is not grammatically correct.
It seems to be a simple mistake. The author began with a sentence like
Opposing reactions activate in the same way.
Then rephrased to say
Emotional pain activates opposing reactions in the same way.
But forgot to remove the second "activate" from after the phrase "opposing reactions", this seems to give a clause with two main finite verbs, which is not possible in English Grammar. Just remove the second "activate" and the sentence is correct.