Wednesday, December 11, 2013

Dopamine the Bus Driver



[correction included]



What is dopamine? What, for that matter, is a neurochemical (or neurotransmitter in this case)? Let's do a brief refresher from Neuroscience 101

You have billions and billions of these:



Neurons, as you'll recall, store your "data" (memories, information and so on). You'll see axons and dendrites there as well. Axons pass on information to other neurons and dendrites are on the receiving end. At the junction of an axon and a dendrite you have a synapse (and recall that you have somewhere around a hundred and fifty trillion synapses). A synapse looks like this:


That's somewhat simplified of course but I can assure you that it is a complicated piece of business, a business that takes place over trillions and trillions of synapses in your brain trillions of times per second for every minute that you will draw breath in your lifetime. The business we're talking about is the transfer of signals from neuron to neuron throughout a given pathway. In other words, if these transactions don't take place, then the information from any given set of neurons isn't "brought on board" whatever it is "you" are trying to do. These ridiculously fine transactions (a synaptic cleft is only about 20 nanometers across and the neurochemicals themselves are very fine indeed) govern a massive amount of brain activity which in turn governs "you". 

So that's a neurotransmitter and dopamine is just one such transmitter of about a hundred but, as we'll see, it's a very major one when it comes to animal and human behaviour. Let's review the dopamine pathways. They look like this:


We briefly touched on that in Neuroscience 101 and now it's time to look at it in a little more detail. Dopamine originates in the Ventral Tegmental Area, a small nodule in the limbic system . The limbic system lies between our more elementary "lizard brain" brain stem hardware and our more highly evolved cortex area. The VTM's job is pretty elementary and it acts in accordance to messages from other more prominent parts of the limbic system. Aside from very advanced practitioners of meditation (whom we'll look at in a fascinating future post), this part of our brain is quite "off limits" when it comes to our conscious control. There's a potential kind of "back door" access to the VTM - aside from meditation - that could initiate a modicum of control but we'll touch on that at the end when we look a bit more at dopamine's complete circuit. (correction notice)

From the VTM, the circuit heads to that little bit of hardware that seems to come up in every discussion on human behaviour, the amygdala. We looked at this highly influential little brain nodule in the previous post and examined a bit how much power it has over our perceptions of and reactions to the outside world, and hence our behaviours. We established then that the amydgala is a major driver of our actions. So if the amygdala is a big part of our actions and dopamine is a part of what drives that, then dopamine is part of what controls a very deep part of who we are and what we do. 

Another key destination is the nucleus accumbens. Research has indicated that this nodule (of which there is a left and right in the respective hemispheres of your brain) has an important role in pleasure; including laughter, reward, reinforcement learning, as well as fear, aggression, impulsiveness, addiction and the placebo effect. So again, we see dopamine plays a role in a key region of many of our most human attributes (as well as those in animals; we just take those to higher and more sophisticated levels).

But there's more.

You can see that the end destination of dopamine is the frontal and prefrontal cortex. As I mentioned in Neuroscience 101, if you want to know where "you" are, it's believed by some neuroscientists to be "there" (though recent evidence now puts this in some dispute). It is also in these areas that we experience theory of mind, the uniquely human abilities involved in such things as understanding how others are thinking, our predictive powers and so on. This is, if all goes well, what makes us "human". As well, you can see it's these areas that are responsible for things such as planning and judgment (something we touched on in two different case studies in the previous post). As dopamine is a major influence on what goes on in there, in order to better understand human behaviour (or your pet's behaviour for that matter) and because the neuroscience of human behaviour is the whole point of this blog, we'd better look at this much closer. 

The Reward System


The dopamine system is very often referred to as our "reward system". So let's examine a bit about what's meant by that. 

As I said in Neuroscience 101, dopamine is one of the most widely studied and understood brain systems in neuroscience and there is little doubt as to what forces it has over animal and human behaviour. Dopamine is very strongly implicated in such basic human and animal drives as motivation, pleasure and euphoria, the fine tuning of motor function, and perseveration. We'll look at just motivation and pleasure today. 

Feeling motivated? Feeling "turned on" by what you do? Feeling "driven"? That's dopamine at work in your emotional centre and in your planning and judgment centre, the frontal and prefrontal cortex. Not feeling those things? That's dopamine not working so well (for reasons we'll touch on at the end). The same with feelings of pleasure - that's dopamine telling "you" that whatever you're doing, it feels "good" which is why dopamine is a major part of our sex drive. The pleasure you feel in sex is derived in part, though not all (we'll examine the other factors in a later post), from a dopamine "hit". Dopamine also can - emphasis on can - keep you motivated to keep seeking sex (often to disastrous results). Why it sometimes doesn't is something we have to leave aside for that later post. 

The evolutionary idea is, you see, to "reward" you with a deliciously good feeling for something beneficial to your survival to ensure that you'll be motivated to not only do that again but to keep you focused on it (and motivated and focused and motivated and focused and motivated and focused in the case of addictions). 

How much does dopamine drive our motivations and pleasures? Robert Sapolsky is a world wide recognized leading expert on dopamine and behaviour so I'll let him tell it. As Sapolsky explains;

dopamine levels increase as soon as we start anticipating a reward. Once the dopamine starts flowing, monkeys and people will work and work and work in expectation of receiving a "treat" at the end of their toil. For monkeys, the anticipated reward can be a grape. For humans it can be a pair of sneakers, a shiny car (you'll recall the example I gave in Neuroscience 101 of a "decision" to buy a new car), an MBA that might lead to a high-paying job, early retirement, a couple of minutes of entertaining diversion, a few seconds of sexual gratification, or the promise of eternal salvation. 

A brief five minute video of Sapolsky explaining this in slightly more, and very fascinating, detail can be found here

I've said that there are parts of neuroscience that are well known and parts that aren't so well known. The dopamine reward system is very much on the known side of the ledger. Literally thousands of experiments and studies done over very many decades on all manner of animal and human research subjects have very thoroughly cemented dopamine's role in our behaviours. As our dopamine system is indistinguishable from that of rats, cats, dogs, primates (or moose as my humorous lead image shows) and so on, researchers can see that our behavioural drives are not all that different from, for example, a rat driven to go through great lengths to press a lever again and again to receive a reward. What's fascinating (and which Sapolsky explains in the video) is that this drive increases when "maybe" variables are introduced. Which is literally what keeps the city of Las Vegas in business

But while we may share a dopamine drive with the average lab rat (and all other mammals), human brains have some additional hardware, that being our vaunted frontal and prefrontal cortexes which is why we're (probably) not going to be motivated by a grape or a bit of rat food like our lower mammal cousins are. It's these so-called regions of "control" that keep us going like rats on a wheel in pursuit of things like sneakers, cars, degrees, trophy wives (or husbands) and all our other "higher" human desires. 

So when we're driven to acquire something - be it an object of desire, money, a sex partner (or companionship) - dopamine is a very large part of what's going on and your drive to achieve goals in life, if it's functioning "normally", is your dopamine reward system.

But the dopamine system is a "blind robot" so to speak. It has no sense of judgment. Hence it will drive you to achieve virtually anything. Which is why dopamine is highly, highly involved in virtually all addictions (including your shop till you drop addiction, ladies, or your manly pursuits, gents). Not only does it have no innate judgment, it impairs yours (as witnessed by its influence on your judgment and planning centres in your brain). 

Is our "highly sophisticated" efforts of planning and judgment merely at the behest of a simple, autonomously running neurochemical? Dopamine won't have complete control - there are other factors - but enormous amounts of research indicates that it does indeed play a major role. This is what I mean by saying we don't really "drive our bus". That all happens in regions that are not only below our conscious awareness but well below our levels of control. 

We're running up to the end of our time today so we're going to have to leave our look at dopamine and addictions of all kinds for the next post. 

Now, I said that there was a "back door" access to the VTA from which dopamine originates. This suggests that there is a modicum of control that we may have over our dopamine system (and thus "us"). This comes from the fact that the reward centre is not strictly an "A to B" road, but one of a loop of output and input. Inputs come from areas it affects and for an idea of how much control this may have, and thus what you may have (as I promised), we have to look into the human species' "social brain", the most highly evolved such area in the animal world. I also said we'd look at why we're sometimes under-motivated and why dopamine may not be "floating your boat". It's a bit complex and a little dicey to explain, but we'll have a go at it. But that, my friends, is for another day. First, however, we're going to look more into dopamine and addictions in another post of case studies coming up in the very next post. 

Correction notice: I initially incorrectly said that the VTM is located in the brainstem when in fact it is part of the limbic system. My apologies. 

Sources:

Too many to list, virtually all of them scientific research papers like this one.The works of Sapolsky are a good place to start for further reading. As always, I have to thank Robert Whitaker, his works and his encouragement over the time I've known him. 

Tuesday, December 3, 2013

The Neuroscience of Behaviour - Some Case Studies

Examples are always a good way to understand complex issues. What we've looked at so far - a bit of a look at the neuronal circuitry of brains, and in particular the human brain - is a bit complex for sure and there are, for most people, some difficult concepts to wrap one's head around. So we'll look at some case studies in which severe behavioural changes were found to be the result of not being morally "bad" or "evil" but because of how specific brain regions had been negatively affected by factors outside of the person's conscious awareness or control. This will give us a more concrete way of understanding brain functions and behaviour. 

Before we continue, however, a few key points to keep in mind.

Each Brain is Different:

Because of genetics and brain developmental responses to environmental conditions, every brain will develop a little differently. This is even true with very elementary brains such as those found in a bee! So it's especially true with our highly evolved and complex brains. 


The Concept of Differing Realities:

By "reality" I don't mean whether a tree is a tree or is just an "illusion". We have objective methods of measuring physical objects and can agree on what they are (in physics terms). No, what we mean here is that because each of our brains are different, each brain will "assemble" what the five senses take in a little differently and thus we will all "see" - IE: perceive - things a little differently. We'll look more into the fundamentals of this later but this is an important fact to bear in mind for now. We may both see a tree, but our individual perceptions of that tree may well be different on many levels. This is well understood by modern science and is no longer in question but we'll save a more detailed look at this for another day.

Brain Regions and Behaviour:

There are, as we briefly looked at in Neuroscience 101, many microscopic components and larger components (assembled from the smaller components) in any brain (animal or human). Each region will have a basic responsibility such as the amygdala for emotions and the basal ganglia and cerebellum for motor movements (all your physical abilities) as two relatively straight forward examples. Other regions will be responsible for higher functions like reasoning, judgment and so on. It is these components and how they work in concert or not that play very large roles, as we'll see, in driving our behaviours. 


These are the basic premises for the neuroscience of behaviour that we have to keep in mind. And with these in mind, let's dive into some tangible case studies.

Phineas Gage:

We're going get two birds with one stone with our first case study. For one, it'll give us a bit of a look into and a lesson about the history of neuroscience and two, we'll see how damage to specific brain regions radically altered a person's character and behaviour. 

The story of Gage is one of the most studied and cited cases in neuroscience history. When you read the remarkable story and see the illustrations, you'll see why. 

This is Phineas Gage, a railroad foreman from the mid-nineteenth century, and in his left hand is a tamping rod that blew through his skull as the result of a mistimed explosion.  




The tamping rod entered through his left cheek and into his brain where it took out a good chunk of his frontal lobes as we can see in this computer recreation of what happened. Remarkably, 
Gage survived.



While Gage the living, breathing, blood pumping body survived, Gage the person did not. His behaviour radically changed following the accident and his recovery. Prior to the accident he was widely known as, in the words of the doctor who handled his case, "possessed of a well balanced mind, and looked upon as a shrewd businessman, very energetic and persistent in executing all his plans of operations". Friends, acquaintances and coworkers knew him to be polite and well spoken and an excellent and responsible foreman on his railway crew. His employers regarded him as "the most efficient and capable foreman in their employ". After the accident he became profane, wild, sexually out of control, and with little control over his actions and almost all chose to avoid him. He became so unreliable that his employers could no longer keep him. 

While his body lived, in the words of those who knew him, he was "no longer Gage". He became a completely changed man. 

What was lost when the tamping rod took out a portion of Gage's brain were areas in the prefrontal cortex, an area critical for reasoning and judgment (which we'll look at in a little more detail shortly). With this region no longer part of Gage's inner galaxies, he could no longer regulate the animal passions welling up from lower brain regions. 


The Man on the Clocktower:

Some of you may recall from the post Why? that I asked why a bright, educated, gainfully employed bank teller and church going man with no previous history of violence would suddenly tote a number of firearms up to a clock tower and gun down forty-three people. That man's name was Charles Wittman and he will be our next case study. 

Wittman's rampage took place in August of 1966 and dominated headlines. Why, everyone wanted to know, would someone seemingly so mild mannered and "normal" do something like this? (and it was later discovered that he'd killed his mother and wife prior to going to the clocktower). How could he do something like this? Wittman himself, it turned out, wanted answers too. In his suicide note, he wrote:

I do not really understand myself these days. I am supposed to be an average reasonable and intelligent young man. However, lately (I cannot recall when it began) I have been a victim of many unusual and irrational thoughts. 

 Some months prior, Wittman had written in his diary:
I talked to a doctor once for about two hours and tried to convey to him my fears that I felt overcome by overwhelming violent impulses. After one session I never saw the doctor again, and since then I have been fighting my mental turmoil alone, and seemingly to no avail. 

Whittman in his suicide note requested that an autopsy be performed on his brain. He got his wish. What the autopsy found was a brain tumour about the size of a nickel which impinged on or compressed three different key brain regions - the thalamus, the hypothalamus and amygdala. As you may recall from Neuroscience 101, these brain components are part of our limbic system and are at the core of many human and animal behaviours. The amygdala is especially pertinent here as it plays a major role in emotional regulation and governs such things as fear and aggression. As the amygdala is so important regarding human and animal behaviour, let's have a bit of a closer look at it. 





It's hard to overstate the importance of the amygdala in human and animal behaviour. All your "data input" through your five senses routes through this bit of hardware common to all in the animal kingdom. The amygdala "tastes" all this input for emotional content as well as attaching emotional content when this "data" is then shuttled around to other regions (including short term and long term memory). Any fears you have will be generated by this brain node, including all phobias. It will play a major role in not only your perception of fear and other emotions (from love to hate and everything in between) and how elevated that is but also how you respond and take action. When I wrote in an earlier post that there are subconscious systems that "drive your bus", the amygdala is a major driver with a great deal of "say" in how you interact with the outside world. 

Neuroscientist David Eagleman explains:

The role of the amygdala in human behaviour has been recognized as far back as the late 1800's when researchers discovered that damage to the amygdala caused emotional and social disturbances. In the 1930s, biologists Heinrich Kluver and Paul Bucy demonstrated that damage to the amygdala in monkeys led to a constellation of behavioural changes including lack of fear, blunting of emotion, and overreaction. Female monkeys with amygdala damage showed inappropriate maternal behaviour, often neglecting or physically abusing their infants. 

 Just a bit further on the limbic system and behaviour in general, it is known that far more messages from the limbic system travel up to the higher cortical regions than vise versa. In other words, the limbic system has far more "say" in what we do than our so called higher facilities located in the neocortex do. This is a huge part of what is meant by "subconscious" systems running the "conscious" you. These systems go awry and "you" go awry. 


Another Brain Tumour Case Study:

This is a case of something which strikes a strong emotional reaction in all of us - pedophilia. Is pedophilia the result of an "evil soul" or a "sick mind"? I ask that you not jump to conclusions here. Let's look at the case of a forty year man with no previous history of wayward sexual behaviour whom we'll call "Alex". Alex went from being a normally behaved married man to one whose sexual preferences suddenly changed. At the age of forty he developed an obsessive and overwhelming interest in child pornography and began to devote a great deal of time to it through magazines and web sites. He wrote later that he wanted to stop but just could not control himself. His behaviour progressed to the point beyond just pornography, he was discovered, charged and was convicted of child molestation. 

For some time prior to his imprisonment Alex complained of unbearable headaches and finally sought treatment. A brain scan revealed a massive tumour in his orbitofrontal cortex cortex. This is an area of the forebrain, or frontal lobes, known to be involved in sexual regulation among many other functions of judgement, decision making and planning. This is a more highly evolved bit of neuronal hardware that separates human sexual behaviour from that of our evolutionary cousins and fore-bearers. 

This handy bit of brain hardware is located here:





Things go awry here (or at least in a specific sub-region of this region) and sexual behaviour goes awry. It is this region of the brain that recognizes "sexual norms" (whatever they may be in your part of the world) and helps regulate your behaviour accordingly. 

And to further illustrate this point, once the brain tumour in Alex's orbitofrontal cortex was removed, his sexual behaviour returned to normal. And to present even more evidence, Alex's behaviour did take a turn for the worse again. But it was discovered that the surgeons had missed a part of the tumour and it had started to enlarge again. The remaining bit of tumour was removed and again, Alex returned to normal sexual behaviour. It was also a huge part of this brain region that was demolished when the tamping rod blew through Phineas Gage's frontal lobes, forever altering his behaviour. 

While this is but one case study, numerous studies and enough research has gone into the relation of this region and sexual behaviour and preferences to firmly establish that damage, underdevelopment or hyper-activation of this region will lead to sexually perverse behaviour (not to mention other psychopathic or sociopathic behaviour). There are also other ways that this important regulating part of the brain can be bypassed or compromised, not to mention how it was genetically and environmentally endowed in the first place, that we'll look at in future posts. 

So I hope those cases gave you some insight into the relation between brain regions and their functions and corresponding human behaviour. Simply put, damage or somehow alter the functioning of a given region and you alter the behaviour of a person.

Now does this mean I'm saying that brain damage or impaired neural development should absolve people of their anti-social or criminal behaviour? Why, as a matter of fact I am. Neuroscience is shining a vast amount of light into what we have traditionally regarded as "responsible" and "moral" behaviour. And unlike our past clumsy attempts at this, now we have have objective methods to examine and understand human behaviours rather than our traditional subjective (IE: opinionated and crudely judgmental) methods of the past. Understanding human behaviour through objective science means not only can we understand why people behave the way they do, but based on this scientific understanding we can better design methods to correct that behaviour that will be far superior to our ancient, crude and tragically ineffective and costly punitive methods. 

As I said in my opening post, I became far, far more compassionate towards my fellow humans when I began to understand how brains really work and that I thought, or hoped, you'd become the same. What I'm asking that you open your mind to is the fact that outwards behaviour that angers you is almost certainly to be the result of a brain problem and is not a "morality" problem or some sort of intentional act. This will take more to establish than just this one post but I want to set the stage for much of what's to come (though it won't all be just regarding moral behaviour). 

Now am I suggesting that we should just allow any anti-social behaviour and forgive it because their brains are broken? No, not in the least. What I'm suggesting is that when we look at a case of anti-social or criminal behaviour that we realize that simple traditional punishments are highly unlikely to "fix" that behaviour y and understand that there are better, more scientific methods for correcting that behaviour. This is not a matter of being a "bleeding heart liberal"; it's a matter of acting on the most up to date science, pure and simple, and getting better outcomes as a result. What we're learning about the brain and behaviours is as literally ground shaking as learning that the earth was not the centre of the universe and will have as profound an affect on the future of human relations and development. 

This is the direction various branches of neuroscience, philosophy and the studies of ethics are heading, all based on the ever emerging scientific understanding of what drives human behaviour and morality. 

"Now", you may very well be thinking, "but those were clear cases of brain damage. Surely not every pedophile (for example) has suffered brain damage?". And you'd be quite correct. We can't pin all wayward human behaviour on brain damage suffered through injury or disease. But as we go along, we'll see that a great number of factors can affect these different regions and thus the behaviour they're responsible for. Genetics play a large role but we'll see all kinds of environmental factors can have huge and profound affects on the development of these regions and how they perform, or not perform at all. 

While regional brain damage and/or developmental problems have been firmly established to affect specific behaviour, animal and human behaviour is not completely governed by "regionology" (my term), that is, it's not completely just damaged or over/underdeveloped brain regions that govern behaviour. Neurotransmitters play a very large role in lighting up certain regions and thus driving behaviour and the neurotransmitter dopamine is a real linchpin here. So dopamine, and its fascinating role in virtually all of our behaviours, will be examined next. 

Sources:

David Eagleman's Incognito: The Secret Lives of the Brain

Rita Carter's Mapping the Mind and The Human Brain Book

Daniel Dennett's Breaking the Spell

Neurobiologist Dean Buonomano's Brain Bugs: How the Brain's Flaws Shape Our Lives

Various works and thoughts of Patricia Churchland

Numerous, numerous science websites such as this one.

Thank you as always for reading along.