Your ear ?
I've been having the same as if they fill up ( like on a plane or when water gets in )
There is a thing called labrynthitis which can do this , it can also effect balance ( as if I'm drunk ) vertigo , other things , there are three types and it can cause / aggravate mental health probs

The glutamate article wasn't in Forbes its was on from NPR article about new treatments for mental health, rizulole and scopolamine were mentioned ,