These muscles under the back of the skull are similar to an animals and have more than 36 times more sensory input to the brain regarding the movement in the spine versus any muscle in the back. Just the simple eye movement from left to right moves these muscles. Subluxation in the 1st or 2nd neck vertebrae can affect these muscle and have a profound affect on the function of the animals entire back. Chiropractic adjustments to correct the upper neck subluxation can literally alter hind end function.