Sexual images trigger chemical reactions in your brain, which in turn compel us to act in specific ways, or be drawn to certain things, or motivated to engage in particular behaviors. It's common nowadays to have consultants whose job it is to find out exactly how your brain interprets images in order to invoke the greatest possible sexual response. Sounds like a fun job, eh? Sex Research Consultant: Totally hot job in 2011.

The mind is a very complex thing, but when it comes to sex, it's really pretty simple. How simple? This is your brain on sex...

Invoking feelings of pleasure, sensuality, and sexual arousal can be quite easily done if you understand how the brain interprets and reacts to sexual stimuli. And you ask, who are the main players in this game of sexual priming? Once again, enter dopamine (he is just about everywhere, isn't he?), and say hello to his little friend, oxytocin.

When we are first exposed (pun intended) to sexually arousing stimuli, certain neurochemical changes take place. Our brain releases dopamine, a neurotransmitter involved in a plethora of functions- pleasure, arousal, desire, and attraction, to name a few. Dopamine also plays a big role in motivation and drive, which is why dopamine-enhancing drugs work well in syndromes like ADD/ADHD, where lack of motivation is an issue. Because of the strong association dopamine has with both arousal/desire and motivation, it is also thought to play a role in addiction.

So how exactly do dopamine and oxytocin enhance pleasure?

After our brain releases dopamine, we feel attracted to the object of our attention. We are compelled to draw closer to it, to experience it more fully. If we are stimulated enough to a point of high arousal, like right before or during orgasm, oxytocin is triggered. Oxytocin is a neurotransmitter that is associated with attachment. When we interface with a person or object, and our brain releases oxytocin, we naturally form an attachment to it. Oxytocin has been found to be a big player in mother-baby bonding, and there have even been very recent studies that show artificial administration of oxytocin makes males more sensitive and helps autistic children form social relationships.

The dopamine-oxytocin (DO) combo is the reason why after having sex with someone, you suddenly feel more bonded to them emotionally. Dr Helen Fisher, Biological Anthropologist, said, "Don't have sex with anyone you have no intention of falling in love with, because it just might happen."

The DO Combo can be a pretty strong weapon in the game of attraction- a pure biochemical love-potion, if you will. And the thing is, you don't even have to engage in sexual activity in order to prime these neurotransmitter responses, which is why fantasies are so powerful. You create the sexual images in your mind, and your brain responds neurochemically, even in the absence of tactile stimuli.

A few weeks ago, I wrote an article titled "Sex Makes You Smarter, Can Virtual Sex Do The Same?" in which I brought up the concept of virtual sex potentially having the same cognition-enhancing neuro benefits as actual sex. The key factor is inducing the same chemical response from the virtual stimuli as you would from the analog. Some people were skeptical. They claimed that there was no way virtual sex could equal real sex, either by sensation or perception.

Now, I think this resistance is mainly due to the over-intellectualizing and idealizing of sex, rather than just going with the science. As long as there is a stimulus-response cued reaction, your brain could care less if it was induced by a steamy night with a Russian supermodel, or by looking through the Victoria's Secret catalog. Dopamine and oxytocin aren't snobby that way. They just want to come out to play, no matter who or what invites them.

If you think about it, fantasies and pornography can be just as arousing as a flesh and blood person, maybe even more so. It all boils down to Classical Conditioning. Research has already shown how paired association of a pleasurable stimulus with a neutral stimulus can cue the release of dopamine from the neutral stimulus following training. You can think of past sexual experiences as the "training condition", and the DO combo as the cued response. After you've experienced the pleasure of sex, certain images and conditions that remind your brain of that experience can cue that DO combo response even in the absence of the the stimulus (sex).

If you are able to deftly prime those neurotransmitters to be released, you can effectively chemically coerce people into just about anything. The mere image of sexual activity or the strong suggestion of it can be enough to cue the response, get that dopamine flowing, and oxytocin comes running in right behind. Is it any wonder why pornography can seem so addictive?

Even continual, repeated fantasies about the same person or activity can trigger dopamine and oxytocin to a degree that you actually start psychologically and biologically bonding with that person/image/idea. Once that bond is formed, it is more difficult to just let it go. Viola! You are officially hooked.

Don't get me wrong here, though. Am I saying that once you respond chemically to sexual stimuli that you are "addicted"? No. Sexual addiction is a whole different topic that I will not be addressing here, at least not today. I still question the validity of that as a bonafide disorder, but I digress.

The point is, all things equal, if you are presented with two things, and one of them induces a sexual response, that is the item or person you will be drawn to. It doesn't matter if it is real, virtual, 2D, 3D, 4D, or all in your mind. All it needs to do is trigger the DO combo, and it is a done deal. Nothing like being a slave to your neurotransmitters, eh?

Next in Part III.. Anticipation and Extended Gratification