I've had Seventh Day Adventists explain to me why eating pork is bad and their stated reasons mainly go to alleged diseases carried by pigs and transferred to people by eating pig flesh. They also mention God's commandments to Israel about clean and unclean foods. And they also argue from the creation story and the story of the flood that human beings were intended by God to be vegetarians. That's all very interesting but it does not go to the heart of the matter which is this "are Christians commanded to keep kosher?". The answer to that question is no but Seventh Day Adventists persist with their line of argument as part of their method of converting Christians to their denomination. You may be wondering why I bring that example up in a discussion about speaking in tongues, well, here is the reason. It does not matter what people allege about brain areas or brain chemistry changes brought about by people using "free vocalisation" since that is not speaking in tongues and it does not matter what people allege about "speaking in tongues" and it's alleged health benefits because speaking in tongues as it happens on the video tapes we see on youtube or that we hear in meetings is never said in holy scripture to be for health - either mental or physical. The one book in the holy scriptures that gives some explanation of what speaking in tongues means is the Acts of the Apostles and it points to speaking in human languages that are heard and understood by those who know those languages.
'Are not all these who are speaking Galileans? And how is it that we hear, each of us, in our own native language? Parthians, Medes, Elamites, and residents of Mesopotamia, Judea and Cappadocia, Pontus and Asia, Phrygia and Pamphylia, Egypt and the parts of Libya belonging to Cyrene, and visitors from Rome, both Jews and proselytes, Cretans and Arabs--in our own languages we hear them speaking about God's deeds of power.' Acts 2:7-11
So the crucial question to ask about those who say they either speak in tongues themselves or say that they hear others speaking in tongues is this "what languages do they speak and can we have that verified?".