Okay so I'll have to agree and disagree with everyone in little bits and pieces.
1] yes, in many cases it's too analytical to discuss the function of the brain as it relates to aiki-movement. -=Unless=- you're just ruminating on different abstractions which keep your mind running or you're a nerd (like myself). If this is you, then read on.
2] The Reptilian Brain is used in Neuromotor Control circles only if speaking in the least of technical terms like saying 'primative brain'. Although I have seen the 'reptilian brain' used more interchangably with the archipallium in psych. circles. If someone wants to discuss the primative brain in terms of movement they often will discuss the metencephalon, which is the cerebellum and pons. The cerebellum is mainly involved in movement. However in the telencephalon the somatosensory and motor cortices are also involved.
Here's a more detailed 'map' of much of the motor pathway...
3] Your muscles do not contain gray matter
, there isn't a place to store memory in the muscles. Memory of a movement is still in the brain. Quick, skillful movements come from developing coordinative structures within trained neuromotor programs, much like complex batchfiles. When you want to walk you do not think of all the requirements, you just think 'walk'. It's like clicking on the 'walk' or 'iriminage' or 'henka' icon on the cognitive desktop.
4]When discussing the fear response or memory of such moments, then it would be the Limbic system to examine, specifically the amygdala and hippocampus. I'll not pretend to be informed enough to speak here as I am a neuromotor control nerd, not a psych. nerd. Personally, when in an emergent moment, I remember everything and it's all slo-mo; be that an assault (of me not by me
), or CPR, or vehicle accident. It is interesting though that many studies of people who have had their hemispheres separated show that what we remember as absolute 'gospel' truth may not be so.
5] Remember talking aikido is not doing aikido. Just as talking about brain function (related to movement) is not -=doing=- movement brain function (okay on a minute
level it -is- but shh). If you want to think about this stuff, okay but it is a micronutrient in your aiki-diet.
My favorite Terry Dobson story ended with O'Sensei saying 'Teru-san you think too much.' and one of my best friends often says to his students "Just shut up and train." because sometimes we -=do=- concentrate too much on the micro rather than the macro.