They found that activating these neurons immediately led to overeating.
We can see that gerund phrases activate these neurons as the subjects of clauses, and the logical subjects of two participle phrases constitute mice ... and adding their ... is the subject of this clause. So these two gerund phrases are adverbials of clauses. We can divide the whole sentence into two parts.
Activating these neurons immediately leads to bing eating, which makes mice eat more than one-third of their daily food ration in just 10 minutes, and increases their preference for high-fat foods.
They found that.
Put these two sentences together and you will get the original sentence.
Identifying the components of non-predicate verbs in a sentence requires a clear understanding of the parts of speech of several non-predicate verbs.
Do sth: in name only
Do/finish: adjective
To-do list: nouns/adjectives
After accurately understanding the part of speech, we can find out its logical subject, find out the sentence trunk and judge the sentence components.