Dopamine And Porn

Poster vaughanbell did not take down Naomi Wolf, he purposely ommited commonly accepted addiction research and twisted known facts to confuse the lay person.

The impression one might get from the vaughanbell post is that dopamine is not involved in addiction, that desensitization is the same as habituation, that the reward circuitry is not involved in all addictions, and behavioral addictions involve different mechanisms from drug addictions. These would be false impressions.

First the author states that habituation and desensitization are synonymous. This is incorrect, yet much of his post relies on this false premise. Desensitization refers to chronic changes present in addiction process that involve a decline in dopamine signaling. One very important, and often measured, aspect of desensitization is a decline in D2 receptors.

-Volkow May Have Uncovered Answer to Addiction Riddle
http://pn.psychiatryonline.org/content/39/11/32.full

-PET Imaging Confirms Link Between Receptor Levels And Cocaine Abuse http://www.sciencedaily.com/releases/2006/07/060716224517.htm

He is correct in describing a declining dopamine response to stimuli as habituation. This is a normal response, for example with hunger. When one is hungry, dopamine rises in anticipation of taking that first bite of a burger. As lunch continues, dopamine declines and we become habituated (satiety). This normal process, which measures the salience or value of stimuli is quite different from the pathological change characterized by addiction researchers. Habituation happens thousands of times a day, desensitization occurs after chronic, usually long-term exposure.

QUOTE:’It’s important to point out that this densensitisation research is almost always on the repetition of exactly the same images. We would clearly be in trouble if any sexual experience caused us to densensitise to sex as we’d likely lose all interest by our early twenties’.

In the above quote he makes 2 points that militate against his thesis. First, he acknowledges that viewing the same images causes a loss of interest (decline in dopamine). I seriously doubt that a porn user would watch the same image throughout one session, let alone day after day. What makes Internet porn so appealing is the ability to move from one image or video to another, one genre to the next. Each new scene provides another possible spike of dopamine. Unlike drugs or food, there are no satiation mechanisms to inhibit porn viewing except orgasm, and many users forego it for hours, either because they want the dopamine buzz, or because they are having trouble climaxing due to brain changes from excess.

– Contextual Novelty Changes Reward Representations In The Striatum
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2838369/?tool=pubmed

Second, the example of a young man becoming desensitized on sex is irrelevant (although most monogamous couples see a decline over time in sexual activity). Internet porn is not sex. As mentioned, the endless novelty that Internet porn provides allow one to seek (dopamine spike) a more exciting scene (dopamine spike), as soon as one becomes bored with the current scene (no dopamine spikes). Porn is somewhat analogous to gambling as vaughanbell described, except with the added incentive of sexual stimuli, and without the loss of money. It’s telling that the brains of pathological gamblers manifest alterations similar to those of drug addicts. Accordingly, psychiatrists are re-categorizing pathological gambling from ‘disorder’ to ‘addiction’ in the upcoming DSM-5.

The neurobiology of pathological gambling and drug addiction: an overview and new findings
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2607329/?tool=pubmed

QUOTE: “With regard to dopamine, it is indeed involved in sexual response, but this is not identical to the systems involved with gambling or cocaine as different rewards rely on different circuits in the brain – although doesn’t it sound great to lump those vices together?”

I believe Wolf was suggesting that all addictions involve the mesolimbic dopamine pathway. Are you, vaughnbell, saying this is not the case? Perhaps cocaine and gambling are differentiated by activation of unique subsets of neurons, yet the “reward circuitry is without a doubt involved in both the salient and hedonic aspects of all addictions. Just for the record, the theory of separate circuits within the dopamine pathways coding for separate stimuli is not a settled matter. This recent study suggests there may be considerable overlap in neurons that code for reward value:
How do dopamine neurons represent positive and negative motivational events?
Masayuki Matsumoto1 and Okihide Hikosaka1
Nature. 2009 June 11; 459(7248): 837–841.

“It has generally been assumed that midbrain dopamine neurons form a unified functional group, all representing reward-related signals in a similar manner1. Our results are roughly consistent with this idea as far as the reward-related signals are concerned. However, clear heterogeneity was revealed when we examined their responses to aversive events.

QUOTE: “Furthermore, Wolf relies on a cartoon character version of the reward system where dopamine squirts are represented as the brain’s pleasurable pats on the back. But the reward is not the dopamine. Dopamine is a neurochemical used for various types of signalling, none of which match the over-simplified version described in the article, that allow us to predict and detect rewards better in the future”

It’s true that dopamine fires for potentially aversive and rewarding stimuli. In other words, for what is potentially salient or valuable. Dopamine is ‘wanting,’ whereas other neurochemicals, such as opioids are ‘liking.’ This is a straw man argument, however, as Wolf’s article was written for a lay audience, and vaughnbell’s point does not negate that dopamine dysregulation is involved with all addictions. Addictions are pathological wanting.

-‘Wanting’ – Incentive Salience
http://www.lsa.umich.edu/psych/research&labs/berridge/research/affectiveneuroscience.html

Here’s one expert who understands a few things. Dr. Nora Volkow, Head of the National Institute on Drug Abuse (NIDA), and one of the top addiction researchers in the world – in recognition of the change in the understanding of natural addiction, is advocating changing the name of the NIDA to the “National Institute on Diseases of Addiction”, as quoted in the journal ‘Science’:
“NIDA Director Nora Volkow also felt that her institute’s name should encompass addictions such as pornography, gambling, and food, says NIDA adviser Glen Hanson.”

http://www.sciencemag.org/content/317/5834/23.1.citation