Here I did further training or that was the beginning of all knowledge, the pictures explain more than 1000 words, even for laypeople like me it was understandable.
From 21.2 to 21.5 everything is there. I link here in case, firstly, everyone can do their own research and, secondly, nobody claims that I would pull all this out of my nose. I've seen everything. I will continue with a presentation by Dr. Veronica Drantz PhD which was created / published on 10/10/2010:
Dr. Drantz on slideshare.net
Another very important source is the book "We Are Our Brains - How We Think, Suffer and Love" by Dick Swaab. Pages 103 - 107. Published by Knaur-Verlag.
Last but not least, Wikipedia with the articles on:
And here you can also read interesting things: (German language)
Forum des VTSM
As the saying goes, don't believe me but do your own research. I have already listed some initial help for your own research here.