mental synthesis vs mentation

mental synthesis and mentation both are nouns.

Word	Noun	Adjective	Verb	Adverb
mental synthesis	Yes	No	No	No
mentation	Yes	No	No	No

As nouns, mentation is a hypernym of mental synthesis; that is, mentation is a word with a broader meaning than mental synthesis:

mental synthesis: the creation of a construct; the process of combining ideas into a congruous object of thought
mentation: the process of using your mind to consider something carefully

Other hypernyms of mental synthesis include cerebration, intellection, thinking, thought, thought process.

mental synthesis (noun)	mentation (noun)
the creation of a construct; the process of combining ideas into a congruous object of thought	the process of using your mind to consider something carefully