26 August 2011

The Science of Pleasure


MOST BUDDHISTS AND MANY NON-BUDDHISTS would not be surprised by statements along the lines that desire and craving are what cause us to suffer. The message is repeated throughout Buddhist literature, both canonical and commentarial. But what is it about desire and pleasure that is problematic? I want to approach this via an overview, culled from many different sources, of the neuro- and evolutionary biology of pleasure.

The feeling of pleasure is associated with activity in a surprisingly large number of areas of the brain with no one area alone that is responsible. This may be because pleasure itself is a complex phenomenon, and it is tied into so many other functions. But we know that pleasure is correlated with dopamine and a group of endogenous (made in the body) opioid compounds known as endorphins and encephalins.

Dopamine, again, is involved in all kinds of brain and gut activity, but it is particularly correlated with such activities as determining the desirability of an object or stimulus; with anticipation and enjoyment of rewards, with alertness or arousal, and motivation. Although clearly involved in these functions dopamine is also implicated in the experience of pain and fear as well. It seems that the same physical mechanisms may be involved in both cases. Research has found that those with more hunger for stimulation, including drug addicts, have higher dopamine levels than those with less. Dopamine levels rise in anticipation of a reward.

The opioid compounds are associated with feelings of pleasure, satiation and well being. Exogenous opioids (those not produced by the body) include the various chemicals found in the juice of the opium poppy: heroin, morphine, codeine; and there are also synthetic opioids like methadone, and pethidine. Opioids are involved in the pain response, so exogenous and synthetic opioids find use an painkillers, with morphine being the strongest known pain relief drug. Most people will know that activities like sex, vigorous exercise, and even singing in groups, stimulate the production of endogenous opioids and these are thought to account for the feelings of well being engendered by these activities. Incidentally, this is probably why chanting together in groups usually leaves us with a feeling of well being, and can be ecstatic.

There are certain features of the physical side of these systems—the chemicals, synapses, receptors etc—that are salient to a discussion of the problems of pleasure. Consider heroin (I was going to write "Take heroin", but realised this might be read as an imperative!). I recently enjoyed Keith Richard's memoir, where amongst other things he describes the process of becoming addicted to heroin and getting off it. Most people find that over time they have to increase the dose this drug to get the same effect. Humans beings build up a tolerance to heroin. What happens at the level of the neuron is that a cell reaches a threshold of excitation through incoming signals coming in via it's dendrites, and discharges through it's axon - thereby exciting the dendrites of other neurons. Reaching this potential always takes a little time, and after the discharge it takes time to recharge. What happens in the synapse is that as the signal reaches the end of the fibre special organelles release neurotransmitter chemical into the gap of the synapse. These travel across the gap and bind with receptor organelles on the dendrite of the receiving neuron. The synapse also has organelles for mopping up stray molecules, and this helps to reboot the synapse ready for the next signal.

In the every day business of the neuron it seldom exceeds its operating tolerances, and has plenty of time to recharge, and to mop up after every discharge. But with intense or repeated stimulation the neuron cannot keep up. And as the individual neurons cannot keep up, the system its forms a part of cannot keep up. So for instance if we flood our blood stream with heroin which binds to all the receptors for endorphins, we get a rush of pleasure. But if we keep doing this the feedback mechanisms which moderate the production of endorphin shut down, because they assume they are not needed. This renders the heroin addict incapable of feeling pleasure or well being without their drug. And when you go cold turkey, as Keef gives heart rending testament to, you go through a period of 72 hours of hell as the body takes this long to restart endorphin production for itself. The acute lack of endorphin leads leads to vomiting, incontinence, shaking, sweating, and global bodily pain.

Of course our brain chemistry is usually operating on more subtle levels than the heroin addict. Isn't it? Not necessarily. Consider that the pleasure we feel is related to endogenous opioids. Living as we do we are exposed to a lot of intense stimulation: refined sugars and fats are not unlike heroin in terms of the neurochemistry: a huge dose of sugar and/or fat overloads our ability to deal with the stimulus and can crash the system. Repeated doses make it difficult for user to experience pleasure when eating ordinary food.

A little fact I picked up recent from the Science Blog, is that men who use pornography on a daily basis often develop erectile dysfunction. The problem appears to be related to overloading the pleasure response - the anticipation of orgasm, the intense stimulation of pornography create a situation where lesser stimuli do not lead to arousal (which is also mediated by dopamine). Following the links on this I discovered that researchers have found that having sex more often with a partner leads to losing interest in them more quickly. This usually leads either to moving on or infidelity, since the new partner freshly excites arousal (for a time); or it leads to interest in more and more intense, not to say extreme, forms of stimulation. Users of pornography often find themselves trapped in the same kind of cycle as the heroin addict - it takes more and more to get the effect you seek, and lesser pleasures lose their savour.

So what have we learned? It seems that seeking out pleasurable experiences produces diminishing returns, and the pleasure response has a natural level beyond which it cannot respond. The pursuit of pleasure is self defeating. This should be no surprise to anyone that has opened a packet of [insert name of favourite comfort food] and just kept eating. But if it is no surprise then how come we can't stop? More or less everyone I know indulges in some kind of pleasure seeking behaviour which has no other goal than to experience pleasure, be it the stimulant effects of caffeine, the 'rush' (and crash) of sugar, or the excitement of driving fast. Even the bliss of meditation can be addictive. Why is it that we do these things in the full knowledge that we'd be better off if we didn't?

I argued before that these urges are biological, evolutionary adaptations. It seems that these systems are not entirely or easily under our direct conscious control. Dieting is hard because confronted by high calorie food we naturally desire it (elevated dopamine) and we get so much pleasure from eating it that it seems a little puritanical to deprive ourselves. But it's even more difficult if we've spent a lifetime training our bodies to expect to get that pleasure, and habituating it to higher levels of stimulation. The sense of anticipation (again dopamine) overwhelms our conscious decision to lay off the chocolate biscuits (or whatever); and since we no longer feel truly satiated without the intensity of refined sugar and fat, then we don't feel satisfied till we've had it. Our pleasure response is tuned so high that we simply don't enjoy anything less.

Of course for most of us this is not a runaway process - we don't gradually build up our sugar intake over time, or have sex increasingly often. But for some it is. In the days before medical ethics committees a man had a wire implanted in his brain that stimulated pleasure. He ended up self-stimulating to such an extent that he lost interest in all other activities including eating! He would have died if the experimenters did not disconnect him, and complained when they did. It is also possible that the mystery of falling fertility rates in the Western World is simply due to the increasing availability, intensity and use of pornography depleting the reserves of sperm (it takes more than a day to replenish them). Look also at the way the media has changed in the last 50 years with increasing use of anger, violence, and sex to 'spice shows up'. We think of this as related to more liberal attitudes, but what if the driver is that we have slowly become less able to respond to more subtle forms of entertainment? It does seem that even if we as individuals manage to find some kind of equilibrium, that over generations the ability to indulge our desires is causing us to be fatter and to seek more and more extreme forms of stimulation and entertainment. Pushing the envelope can lead to experiencing new pleasures - just as someone bored with a partner can find a new person exciting (for a time). But once we start pushing the envelope, the returns diminish, and we feel the need to keep pushing. We are probably moving along the axis in the wrong direction and should be thinking in terms of less extreme forms of stimulation, indulged in less often, in order to maximise pleasure and satisfaction.

So the picture that is emerging from neuroscience and evolutionary biology is one which leads us towards conclusions that are not new. Find pleasure in what you are doing, don't do things only for pleasure. Moderation is a virtue, and abstinence does make the heart grow fonder. Spacing out intense stimulation - whether food, sex, TV, movies, drugs, or whatever - gives the body time to reset and allows us to feel pleasure more easily, more naturally. Cutting down on strong stimulation allows us to appreciate more subtle experiences.

Satisfying natural urges is probably not a bad thing, but we need to recall that we have not lived in 'natural' circumstances for something like 10,000 years (since the dawn of agriculture and civilisation). People often cite the middle way as justification for their indulgence, and I like to remind them of what the early Buddhists considered the middle way in terms of lifestyle: no family, no job, one meal a day, no possessions, no sex, several hours of meditation etc. So, what is natural? In fact most of us could do with drastically reigning in our desires and impulses and the language of early Buddhist ethics begins to seem highly relevant again. The Buddha reportedly said:
nāhaṃ, bhikkhave, aññāṃ ekadhammaṃ pi samanupassāmi yaṃ evaṃ adantaṃ, aguttaṃ, arakkhitaṃ asaṃvutaṃ, mahatp anatthāya saṃvattatīti yathayidaṃ, bhikkave, citta.

I do not see any other single thing, monks, which left untamed, unguarded, unprotected, unrestrained, leads to so much misfortune: i.e. the mind [citta].
And though this kind of thinking is deeply unfashionable these days, in light of the research I've been exploring it starts to make a new kind of sense. Guarding the gates of the senses seems more important than ever.

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