There are two distinct differences in the areas of the brain associated with sexual arousal and emotional responses typical of being romantically involved, and using brain scans. Scientists were able to decipher the distinctions people make-in their brains-when presented with sexual stimuli and then pictures of their wives and/or girlfriends.
Subjects who had very recently entered into new love relationships were hooked up to electro scanners and given a series of questions to answer pertaining to their new loves. Their levels of dopamine soared when answering the questions, and appeared mostly to stimulate the right side of the brain, usually associated with rewards that are not typically in the instant gratification section. This was thought to be because romance and love is not part of instant gratification, as is thought to be sexual encounters, porn, and impulse control associated with the left side of the brain. When the same subjects were shown sexually explicit material or answered explicit questions, the scans on the left side of the brain reacted.
More importantly, the areas of the brain which are thought to act as the relationship matures changed strongly when these same questions were answered by couples who had been involved for several years, leading scientists to believe that as we mature in our relationships, so does our brain activity in response to that relationship. This could also explain why couples who are very much in love also experience a sense of the spark going out of their relationship after a few years. It's not that they aren't attracted to each other any longer; it’s that their brain waves have matured. This could give much hope to couples thinking about separating because they don't know what happened to the romance and sex in their relationship. This breakthrough could save you thousands on couples counseling, and give the hope that as the two of you move through this area of your relationship-and you will move through it, studies also show that this is a growth area for couples, not the end of the partnership- you will come out on the other side even more attracted to each other than before.
During the fifties and the beginning of the sixties, these types of studies where not even thought of, couples stayed together even when it seemed impossible. With the explosion of divorce becoming popular in the seventies and more couples separating in order to find them, the need for these types of brain wave studies became very necessary, and a good thing, too.
If you and your partner are in a rut, it's not the right move to separate. Stay together and give it some time, there are other things you can do to spice up your relationship and still stay together. Love is still by far the strongest of all of the emotions.