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.

the brain that changes itself

I got into an argument with The Boy a few days ago about 'super-stringy' calf fibres (his terminology, not mine - I think they're actually called fast or slow twitch fibre compositions). While I'm all for interdisciplinarity, my entire academic career testifies to this claim, attempting to overlay anthropological theories onto neuroscience just doesn't work for me. Basically he was trying to argue that nature presided regally over nurture.

Being, as I am, mildly obsessed with neuroscience (I'm already planning a career change at 37) I know that most neuroscientists, but especially those with a particular interest in neuroplasticity would say that the nature/nurture debate is largely irrelevant as the two are completely inter-related.

Not only with sports, but with your ability to play a musical instrument, or to paint or compute complex mathematical equations - natural talent or genetics can only take a person so far. So yes, perhaps Michael Phelps is 'built' with the 'perfect' frame for swimming (whatever that means), but if he was more motivated to study theoretical physics and became one of our greatest physicists, no one would say 'he was built' for theoretical physics. Likewise, while proponents of the nature theory might argue that Lance Armstrong is a great cyclist because he has one of the greatest V02 max readings ever seen (an individual's maximal rate of oxygen consumption), the same genes that are so often attributed for his success also contributed to the development of his nonseminomatous testicular cancer.

I'm coming at the elite athletics side of this from a strictly laymen position, but after a little bit of reading, I found something interesting about the natural gap between V02 max readings between men and women. Sports physiologists supposedly claim that genetics play a major role in a person's VO2 max and that heredity can account for up to 25-50% of the variance seen between individuals, thus leading us to believe that nature triumphs over nurture and that plastic change is impossible. Where this becomes interesting is in a comparison between untrained girls and women, who typically have a maximal oxygen uptake 20-25% lower than untrained men. However, when comparing elite athletes, the gap tends to close to about 10% and if V02 max is adjusted to account for fat free mass in elite male and female athletes, in some studies the differences disappear. So something else is going on here besides just genetics. Training, nutrition, psychology, etc., must account for the ability for our bodies (and brains) to major changes.

It's always in running - especially sprinting - where people tend to say that speed is without doubt the result of genetically determined factors meeting training effects. Common belief is that if you took a random sample of children from West Africa and another from a western European country, on average, the West Africans will be faster in a sprint race. Explanations for this can not be precise, but tend to centre around natural ability and physiological determination.

Now to get to the whole point of this post. I recently purchased a very interesting book by psychoanalyst Norman Doidge called The Brain That Changes Itself. By some brilliant coincidence The Philosopher discovered that Dr. Doidge was giving a talk at LSE last night. We went, we listened, we were entertained. It was interesting - he wasn't as lucid in person as in his book (which I thoroughly recommend if you have any interest how your brain is profoundly affected by your everyday environment - you'll never look at porn websites again!), but still it was good fun.

The point about running and the difference between Africans and Europeans reminds me of a great anecdote in Doidge's book. In 2003, researchers from Sweden's Lund University did some research with the Moken sea gypsies who live in the archipelago of Burma and along the West Cost of Thailand. When you dive underwater and open your eyes, everything appears slightly blurry. Focusing depends on the curvature of the lens and the difference between the index of refection of the eye and the surrounding medium. Air has an index of refraction of 1, the cornea 1.376 and the aqueous humor 1.336. The index of refraction of water is about 1.33. Because of the small difference in the index of refraction of water and the eye, the lens must become very curved to focus light on the retina. Living on land, there was no evolutionary need for the lens to become this curved, so objects are out of focus when we open our eyes under water.

Unlike most of the rest of us, the sea gypsies maximally constrict the pupil to see accurately underwater - this is not a genetic attribute - rather it has developed over time through repeated exercise and use. Moreover, there are studies which have demonstrated that European children can learn to demonstrate this same pupil constriction with practice. This is a great and easy to understand example of plasticity and the 'use it or lose it' theory of the brain: we're talking about use-dependent cortical reorganisation here. This isn't saying that if you believe in something enough you can do it or master it, but that if you create an environment where you are constantly having to exercise a particular function in order to improve, then surprising things are achievable.

If I can be asked, I'll write up a part two sometime soonish. There are some very interesting connections between behaviour and environment (remember the porn?) that will seriously get you thinking about the habits which form your day to day existence. We may not have the inclination to be world-class athletes, but surely we'd all like to be a little bit better at something.

Like Doidge says, use your brain or lose it. And with new(ish and admittedly slightly hysterical) studies showing that age-related cognitive decline beings as early as 27, I'm pretty sure that means all of us could stand to do a bit of brain spring cleaning...

PS If you are really a glutton for punishment and want to know more - V.S. Ramachandran, a brilliant neuroscientist, gave the BBC Reith Lectures in 2003 which are very stimulating yet quite approachable.