REGIONAL CEREBRAL BLOOD FLOW (RCBF RCBF): Regional cerebral blood flow monitoring may help boost the validity of the regional localization theory, in which specific parts of the brain control specific functions.. measure of the blood flow in a specific area of the brain, using positron emission tomography (PET scans) and/or single photon emission computed tomography.
If a dog goes on his back to you he is accepting you as his master. This is part of the answer but here's a little more in-depth version as reported by USA Today. In general, dogs lie on their back for three reasons.
The exact opposite is the dog with her tail tucked between her legs. Whether she's talking to you or to another dog, the message is the same: I give up!. Just because a dog's tail is down doesn't mean she's frightened, though. A relaxed dog may keep her tail lowered, although not between her legs.