Thursday, 2 April 2009

the brain that changes itself, part 2

If you want to experience the power of neuroplastic change, I suggest you develop a porn habit.

I promised a discussion of pornography and plasticity in my last post on the topic and I'll try to give at least a bit of an explanation here.

Pornography appears, at least on a surface level, to be a purely instinctual matter: sexually explicit images trigger instinctual responses which are supposedly the product of millions of years of evolution. But supposing that were true, we would assume that pornography would be static and unchanged over the years. We would expect that the same triggers, body parts and proportions that appealed to the first consumers of porn would still excite us today.

Obviously this is not the case at all, and you only have to hop on the web to find endless evidence which counteracts this claim. Pornography is a dynamic phenomenon that perfectly illustrates the progress of acquired tastes. Thirty years ago 'hardcore' porn typically meant the explicit depiction of sex between two partners, while softer porn usually meant pictures of women - on a bed or at a dressing table - in various states of undress. Now, hardcore has evolved into something completely different and its subsections have increased ten-fold: BDSM, group sex, anal sex, you name it, pretty much anything goes - but quite a lot of hardcore porn fuses sex with violence, hatred, and humiliation (on either gender, not necessarily traditional gender roles). Softcore porn is now what hardcore was a few decades ago, which even Jacqui Smith's husband can download from cable TV. Those softcore images of women from 30 years ago are now entirely commonplace and show up in all forms of mainstream media.

This wider cultural trend speaks to the more particular effects on the brain maps of individual consumers. Like other facets of human sexuality and romance, the key issue is tolerance. On the cultural and individual level we are like drug addicts who can no longer get high on the images that once turned us on. And the danger is that this tolerance will carry over into relationships, leading to ah hem...potency problems and new, at times unwelcome, tastes. I'm not saying that porn is evil or you'll go to hell for using it and casual, irregular use is probably not much of an issue. But what people don't realise is that, like any other addictive behaviour, all addiction involves long-term, sometimes lifelong neuroplastic change in the brain.

Pornography is more exciting than satisfying because we have two separate pleasure systems in our brains, one that has to do with exciting pleasure and one with satisfying pleasure. The exciting system relates to the 'appetitive' pleasure that we get imagining the things we desire - sex or good food - and this chemistry is largely dopamine-related which raises our tension level. The second pleasure system has to do with satisfying the 'appetitive' pleasure - when you actually get the sex or the food. Its neurochemistry is based on the release of endorphins, which chill you out and lead to that calming, fulfilling sense of pleasure. By offering your brain an endless stream of sexual objects for excitement, porn hyperactivates the appetitive system. Regular viewers develop new brain maps based on the photos they see and the videos they watch. And because it is a use it or lose it brain, when we develop a new map area, we long to keep it activated. Just as our muscles become impatient for exercise if we've been sitting all day, so too do our senses hunger to be stimulated.

It's unbelievable how much people take this repetition for granted. Our activities significantly alter our brains and thus our brains have the ability to significantly alter our actions. We are creatures who absorb the environment around us, who suck up stimuli like Brawny paper towels. There's an interesting theory linking the increase of autism among children to the fact that more of the world's population live in cities. The constant stimulation of children who live in cities leads to a lack of an ability to differentiate between white noise and important noise - these are the sort of factors which contribute to autism developing later in life - an overstimulation of the nucleus basalis (the part of our brain that allows us to focus our attention - during a child's critical period, a nerve growth factor called BDNF or brain-derived neurotrophic function, turns on the nucleus basalis and keeps it on throughout the entire critical period - this is why we learn language (well, learn everything really) so easily as children and find it much more difficult after the critical period when the nucleus basalis is only activated by periods of directed concentration) means that the children take in too much information and find it difficult to focus and differentiate later.

If you're still with me, let's go back to sexuality and also bring back the idea of nature/nurture.

If another way of considering the nature versus nurture issue is acquired versus natural tastes, then plasticity has yet another interesting contribution to make. Sexual tastes are often acquired, influenced by cultural tastes (why so many people find Brad Pitt and Angelina Jolie attractive) and experience (if you had a blonde lover and he was fantastic in bed, you might be more likely to believe that blonde men make better lovers) and is often acquired and then wired into the brain. Sexual plasticity is a good overarching metaphor for neural plasticity. People can have fluid sexualities, engaging in relationships with white women, black men, find younger people attractive, hell - some people find cars or shoes attractive. Given that we accept sexuality as an instinctive and biologically necessary behaviour, the possibility for the variety of our sexual tastes is bewildering. As Doidge points out in his book, instincts generally resist change and are thought to have a clear, non-negotiable, hardwired purpose, such as survival. Yet the human sexual 'instinct' seems to have broken free of its core purpose of reproduction, and varies to an extent not seen in other animals. Anthropologists have demonstrated that for a long time humans did not know that sexual intercourse was required for reproduction - it was a learned behaviour then, just as it is now. This detachment from its primary purpose is perhaps the ultimate sign of sexual plasticity.

Sexual plasticity may also be related to dopamine. Dopamine loves novelty and just like the body builds up a tolerance to drugs if they are abused, so does the brain develop a sort of tolerance of a lover which inevitably leads to the loss of that romantic high (you know, the honeymoon period). This change is not so much a sign that either lover is inadequate or boring, but that their plastic brains have so well adapted to each other that it is harder for them to get that same dopamine buzz they got at the beginning when every experience was new and novel. There is this idea that the partners are responsible for providing the relationship's stimulation, but what is interesting is that when this bored couple engage in new experiences together they are using novelty to turn on the pleasure centres (releasing dopamine), so that everything they experience, including each other, excites and pleases them.

So dopamine and pleasure seeking can, unsurprisingly, be both good and bad.

To keep the mind alive you must learn something truly new with intense focus. This is what will allow you to both lay down new memories and have a system that can easily access and preserve the older ones. Take a physical activity, dance for example. Simply performing the movements you have already learned will not keep your motor cortex in shape. This is why an activity such as learning a new language as an adult is so beneficial for the brain. Because it requires intense focus (if you're doing it properly, that is), studying a new language turns on the control system for plasticity which helps to lay down and maintain the new memories. If you're learning a new language under a method which supplies some kind of reward for progress, even better as this stimulates the control system for plasticity to keep up its production of dopamine and acetylcholine - both of which enhance the amplitude of synaptic potentials following long-term potentiation in many regions - i.e. reward during learning triggers the pleasure centres in your brain (the dopamine), which makes you want to keep learning and the acetylcholine enhances the synaptic potential of these new connections.

So turn off the porn and figure out how to make the brain's pleasure centres work for you and not against you.

3 comments:

Dan G Swindles said...

Great article

The implications are particularly disturbing as vast amounts of hardcore porn is only a google search away, and I vaguely remember reading about the huge % of children who regularly watch porn

I wonder if we'll be looking at an increasingly sexually dysfunctional society in the future? It would be a great shame if this was coupled with progress in greater sexual freedom and tolerance

Mr. Propter said...

Crystal lady, it is I, Dikaiopolis and Cleisthenes, under a new disuguise. I stumbled across this while searching for articles about neuroplasticity (and porn). I'm glad to see you're out of Classics and still writing this blog. Last year I was attending a meditation class taught by a neuroscientist, and was also dating a grad student in neuroscience for a while. I'm looking to write something on meditation, chronic pain and neuroplasticity at some point, and have read Doidge's chapter on 'the Dark Side of Neuroplasticity'. In the meantime, I will install some porn-blocking filter on my laptop. Regards to the Philosopher, if he is the Finnish conservative I take him for.

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