Author: Marc

That’s a quote from a recent reader, and I think it’s a fabulous metaphor. The idea is that brains and the chemicals that run them come from molecules that have been part of the evolutionary marketplace for a very long time. So the “code” that our brains use to operate (and to have fun) is easily mimicked by compounds out there in the world. When we find those compounds and consume them, we hack our own nervous systems.

Indeed, our major neurotransmitters are extremely old. So are the neuropeptides (which include opioids). I read somewhere that male lobsters stand up and rear their claws when they get a spurt of the peptide vasopressin…which comes from their own brainstems. Vasopressin is an important neurochemical for inter-male aggression in humans! A humbling thought. So not only do we share neurochemicals with extremely ancient ancestors and extremely distant cousins, we even share their functions.

Now pre-hominids weren’t much good at extracting stuff from plants. Hands are really useful for that. But hominids have been around for a couple of million years, and even the period of agrarian civilization, about 5-10,000 years old, is plenty of time to experiment with the profusion of plants that make feel-good chemicals. The fact that neurochemicals are cobbled together from existing molecules, as pointed out by the same reader, is hugely important. That’s what improves the odds that our favourite neuromodulators will have cousins in the plant world. All we had to do was find them, refine them, and eat them (or smoke them or snort them or shoot them).

According to Berridge’s theory, dopamine doesn’t make you feel good, but it makes you feel engaged and excited. It’s opioids that make you feel good. The fact that opioids automatically release more dopamine means that liking and wanting are closely bonded. Unfortunately, though opioids increase dopamine flow, the reverse is not the case. Dopamine flow just makes you try harder. Hence, whether you get your dopamine rush from methamphetamine, coke, from planning your next batch of cookies, from anticipating the next rib, or from the vicious cycle of addiction itself, there is no pot of gold waiting at the end of that rainbow. Unless you put it there yourself.

We are indeed a species who hacks our own brains with the stuff we find lying around in nature. And since dopamine and opioids are so crucial to the reward system, it was almost inevitable that we’d find them, use them to hack our brains, use them some more because they work, and then start to work hard to get them. Thus, it’s almost inevitable that we’d evolve into druggies. And, I suppose, just as bad backs are an unfortunate byproduct of upright posture, it’s almost inevitable that many of us would become drug addicts.

Last post, I lamented the fact that I spend most of my lunch looking forward to the next bite (and not tasting the present one). I blamed this habit on the role of dopamine in the ventral striatum: to anticipate rewards, work toward them, and focus attention on what’s next. Here’s a picture (a reconstruction, obviously, as cell phones lacked camera functions in those days) of Homo habilis having lunch. H. habilis lived about 2 million years ago, and is thought to be the first member of the Homo genus. In other words, he’s our direct ancestor, and no doubt our brains resemble his in many ways. Well, we have bigger frontal lobes. But…so what? How often do we use them to advantage while eating lunch? I use my frontal lobes to read the newspaper while having lunch, which is an elaborate way to avoid any contact with the taste of my food.

What does any of this have to do with the psychobiology of addiction? Goal anticipation equals craving when the goal is out of reach. This is a common state for addicts, even for recovering addicts. When the goal (let’s say more ribs) is in reach, then the dopamine surge simply directs you take more. The theory I follow for understanding the addicted brain divides motivated behaviour and pleasure into two distinct functions: wanting and liking. This theory has been proposed and defended by Berridge and his colleagues for over 10 years, and as far as I can see, it beats other theories hands-down. According to Berridge, wanting is subserved by striatal dopamine, and liking is subserved by…you guessed it…opioids. I cover all this in detail in my book, but the thumbnail version is this: When you like something (and get a rush of endogenous opioids), it is adaptively important to get more of it. That requires wanting. Opioids make you feel good, but they also increase dopamine flow to the ventral striatum (from the VTA, ventral tegmental area, in the midbrain). So dopamine takes over from opioids, by which means wanting takes over from liking. Your brain lurches into gear: where will I find more? how will I get it? I can’t wait! The symptoms of craving are obvious.

Our ancestor, whose mesolimbic dopamine system was pretty much exactly the same as ours, looks to me as if he’s saying: “Hmmm, not bad, tastes pretty good. Where can I get more…?” He’s just at the shift point from liking to wanting. Look at the creases in his brow. I’ll bet you he’s already thinking about the next bite.

I want to thank those of you who replied to my query. A lot of your advice converged to a few simple themes:

1. Keep blogging

2. Go with reviews of interesting research, bridges and connections between data and interpretation, opinions about where we are and where we’re going in the science and policy of substance use (and its discontents).

3. The style and form of the blog can be intriguing in themselves. Let the blog wander but keep my own voice.

4. Let it be personal, yes, and detailed, and most important, don’t limit the blog to addiction. There are many other topics, only loosely related to the neuroscience of addiction: the science of behaviour, the neuroscience behind clinical disorders, issues concerning willpower and self-control, and my thoughts while stuck in traffic or eating lunch. I agree: there’s lots to talk about!

Today I won’t share my thoughts while in stuck in traffic, but I will share with you what I had for lunch.

What I had for lunch was dopamine, and plenty of it. Isabel had made these incredible ribs the night before. Thick, dark, juicy sauce stuck intimately to the most tender meat, which pulled easily off the bone in my exultant teeth. (Hope not too many of you are vegans) So you’d think I’d be very aware of the taste — the delicious taste — of these succulent morsels — brought to you by the opioid bath (internal, please!) washing over those orbitofrontal neurons. But I was hardly aware of the taste or texture at all. What I was aware of, during the execution of each bite, was the following bite. Dopamine, which is the chief underpinning of anticipation, drove my attention to the near future — the next bite, getting the right amount of sauce on the next piece to enter my mouth — even as I commenced on the present bite.

How stupid is that?

My kids also gobble down their food without tasting it. I tell them, “Taste every molecule!” But they don’t, and neither do I. During my rib extravaganza, I was somewhat aware of the waste of consciousness, and not pleased about it. I tried to slow down. I reflected on how different the experience of eating is when you’re sitting at a nice restaurant, with candles going, very aware of the moment, I think, but perhaps more aware of the imperative to be in the moment. That’s not quite being in the moment. It’s just another algorithm for focusing on the future.

What I’m railing against is the  power of dopamine to suck you away from the now, into the future. It’s so ubiquitous. For example, my last post was entitled “What’s next…?” That’s where we live: in the future. The purpose of dopamine uptake into the ventral striatum is to define and sharpen the focus of attention — attention to the next goal, or the next step toward the next goal. After all, present pleasures are in the bag. Future…opportunities…are where one’s attentional focus can really make a difference. It is of no adaptive advantage to focus on what’s happening right now. What’s happening right now is just about over.

I guess the upside is that this state of affairs provides steady employment for Buddhists, meditation teachers, contemplatives, and so forth. They’ve got lots of work to do, mainly in helping us resist impulses nested deeply in our brains.

But for now, I’m feasting on dopamine — the exquisite  anticipation of the next bite. And that’s pretty typical of the evolutionary lunch stand where we gobble down what we have and prepare for what’s next. It’s also the common neural pathway of all addictions.

I have to figure out this blogging thing. About 2 weeks ago I was invited to host a blog on the Psychology Today website. So I set up a sort of parallel blog there, with most of the same posts. I’ve been making them a bit shorter and punchier for PT, and I’ve been providing more detail, including neuro detail, for my home blog (this one).

But I’m slightly mixed up on where to go from here. Should I retain two blogs? My PT blog gets up to 500 visits per day. It’s PT, after all. This one gets anywhere from 10 to 50 most days. And why bother with two, after all? Especially if they cover more or less the same content? But I like having my OWN blog/site, and all those flashing ads on the PT site annoy me. I have old-fashioned eyeballs.

Maybe the thing to do is to get more flowy — more personal, more newsy — and move away from essay-like postings. So says Isabel, my wife, who did a very successful blog during our last couple of years in Toronto. I like blog writing. It’s great to knock off a piece of…something…in an hour or so, rather than spend six months on a scientific paper that very few people will ever read. But the flow of my life is pretty calm at the moment, and I’m not going to try to interest people in what I’m having for lunch or my thoughts while stuck in traffic.

People who read this blog are, I think, I hope, either those with present addictions, past addictions, or people interested in the science and/or treatment of addiction. So what’s to flow about…that might be of interest to you? My addiction is mostly past, not present, though I have struggled with it in recent times. A “memoir” article in Toronto Life (November 2011  issue) recounts my difficulty getting off oxycodone last spring, after a stint of severe sciatica and recovery from spinal surgery. And I sometimes drink more than I should. So, yeah, I’m not completely in the clear. As far as I know, no addict ever is. But I’m in good shape these days.

I recently found a blog by someone who is currently — like this month! — getting off alcohol. She’s on week 2 or 3 of recovery by now, and I really admire her blow-by-blow description of what it’s like to quit: how it feels, the voices in her head, the spikes of craving, and the relief at moving on. That’s one kind of flow that can be of real interest to people in the addiction world. But my struggles just aren’t that dramatic these days.

And then there’s all this late-breaking news on the science, psychology, and politics of addiction. A special issue of Nature Reviews Neuroscience was recently dedicated to addiction. And the Addiction Newsfeed from Science Daily pulls all kinds of interesting stuff from just about everywhere — Click on Home and scroll down to see it. I can be more current and more, I guess, opinionated if I follow this stuff more closely. Maybe I’ll try that for a while.

I’m just thinking out loud at the moment. But I’d love to hear your thoughts as well.

Steven Pinker (the evolutionary biologist) recently released ANOTHER book, entitled “The Better Angels of Our Nature.” In it he shows how violence has declined over the last 30,000 years of human affairs. And he says that’s due to the rise of competing characteristics, like cooperation, self-control, and empathy. According to Pinker and others, human characteristics like these arose from brain evolution. For example, our urge to cooperate evolved over time, because the laws of natural selection favoured a brain with plenty of social circuitry. (A lot of this circuitry is thought to be in the medial prefrontal cortex, just in front of the ACC.) When a tendency or a characteristic improves your ability to function and survive, and especially your ability to produce and raise children, then you’re more likely to have more kids (who also have more kids, who also have more kids) than your neighbours. I mean, wouldn’t you pick a cooperative, empathic, self-possessed partner over a raging savage to have your babies with? So then the biological quirk that gave you that quality — in this case a more humane brain  — becomes a part of human nature. It beats out the competition.

What about addiction? We know that the tendency to pursue specific rewards (drugs, booze, porno, food, internet gambling, feet if you’re a foot fetishist, etc.) grows easily into addiction. That’s why so many of us are addicted to something. And we know that certain brain processes, like the rise in dopamine whenever you’re reminded of the thing you want, are what make addiction happen. In fact, much of the prefrontal cortex seems prewired for addiction. Increased dopamine flow cultivates more and more synapses in the orbitofrontal (lower/prefrontal) cortex, and in the nearby ventral striatum. These synaptic networks come to represent the details, angles, images, and the beatific value of the thing you crave. Which dredges up more dopamine from the brain stem, so you wire up more synapses in the addictive network, and on and on it cycles. No wonder we’re easily addicted. Our brains seem perfectly designed for it.

Addiction as a byproduct of brain evolution

Yet, brains did not evolve to make us better addicts! That wouldn’t make sense. Addicts are not very functional (except when it comes to meeting certain needs), they often don’t survive as well as most, and they make relatively lousy mates and parents. The brain processes that underlie addiction should have been weeded out, not strengthened, by natural selection.

Except that natural selection (evolution) doesn’t explain everything about being human. (As argued most forcefully by Stephen Jay Gould, one of Pinker’s detractors.) A lot of human characteristics are byproducts, accidents, that arise from structures designed for different purposes. For example, half the people I know over the age of 35 have back problems. Did back problems evolve because they’re adaptive? Of course not. Back problems are a result of walking around with an upright spine, something our ape ancestors didn’t have to worry about. Having an upright spine is good for a lot of things. Like having your hands free to do stuff while your feet take care of locomotion. In the same way, I think that addiction is a byproduct (a nasty one, quite often) of having a brain designed to maximize goal-pursuit in an uncertain world.

A circuit evolved for goal-pursuit

The circuitry connecting the orbitofrontal cortex and ventral striatum is a beautifully crafted machine for learning what you like and pursuing it with single-minded purpose. Its fuel is dopamine, sucked up from the midbrain (upper brain stem). And this machine sends messages directly to the premotor and motor cortex, which trigger behaviour, action, in pursuit of the good things in life. This machine evolved so nicely because it’s really really important to pursue valuable goals. Immediate goals. And not all those goals can be prewired from birth. You need to learn them as you go along. So the goal-pursuit circuit is flexible. It learns. It’s always open to try new rewards, and then to pursue them if they’re as good as they look (or taste, or smell). That’s why we pursue goals ranging from fruit, to fries, to Ferraris. We go after money — a relatively recent invention — because it’s really nice to have. It makes life better. We go after romantic partners deemed to be attractive by movie and magazine images. We can learn to go after anything, full bore, if it attracts us. And that’s how we get ahead in life.

But it’s also how we get addicted. The goal-pursuit circuit is a bit too flexible. Cocaine high. Oh yeah. That feels good. Want more. Got to get it. That drink at the end of the day. Feels good. Want it. Stop at the liquor store on the way home. These tendencies eventually cause us a lot of suffering, but they are simply byproducts of a brain that evolved to seek rewards, based on their attractiveness, and to pursue them with almost relentless energy.

When your back-ache gets bad enough, you start doing physio or yoga, so that you can use your upright spine to its best advantage. When your addiction gets bad enough, you’d best figure out how to use the goal-pursuit circuit for what it’s designed for: to be successful and happy, to avoid suffering, and — of course — to feed the little ones back at the cave.

This post also appears, with a bit less detail, on my “other” blog on the Psychology Today website. I know, I have to consolidate…