Craving (7 page)

But feelings alone cannot explain the heartbreaking self-destructive results that cravings produce. They result from actions that are contrary to the person’s own health. How are people tricked into taking such actions? That’s exactly where the prefrontal cortex comes in. Remember that Phineas’s judgments changed when he lost a large chunk of his prefrontal cortex. The neurons in the NA project into many different brain regions. Most of the neurons in the NA release GABA. The prefrontal cortex receives direct and indirect input from other nuclei in the reward system, but it’s fair to say that the activity of the prefrontal cortex is directly and largely influenced by the activity of the rest of the brain’s reward system.

So just what is the prefrontal cortex that Phineas lost when the rod shot through his skull? What is it responsible for, and how does its function relate to craving? The prefrontal cortex is extraordinarily complex in its roles and functions; entire volumes can (and have) been written on its purposes. However, perhaps the most important reason that you have a prefrontal cortex is to perform what psychologists call executive functions. Executive functions are the components involved in higher-order decision-making. These include planning and executing voluntary actions. This part of your brain is critical to working out what actions you will take, comparing the results you got to what you expected would happen, and changing your behavior in response to that new information. This part of the brain is more complex and developed in humans than in rats. For many reasons, including our more advanced prefrontal cortex, people have the power to make rational decisions that rats cannot. But when our prefrontal cortex is damaged (as Phineas experienced), or is affected by addictions, we fail to make such decisions and often act against our own interests.

One extremely important purpose of the prefrontal cortex is to suppress habitual behavior. Habits are beneficial: they are critical to survival, and they enable us to solve everyday problems and go about our lives without having to think through every decision, which would otherwise result in decision paralysis. However, sometimes people need to act in direct opposition to their habits if they are to achieve their goals; in fact, this capability is critical to the basic act of questioning, and without questions, there can be no choice. One of the most brilliant men I have ever met, and one of my most influential professors, Alec Horniman,
¹³
is fond of saying, “People are creatures of the habits they created. If most of our behavior is habitual, how do we increase our choice abilities?” Well, to the extent that we can, it’s our prefrontal cortex that enables us to do so. Since suppressing habits (until we actually change them) is critical to addressing cravings, we will be hearing a lot more about the healing aspect of behaving contrary to your current habits later.

The prefrontal cortex is involved in the ability to be spontaneous, but also in the ability to suppress spontaneous, impulsive behaviors when they are socially unacceptable or detrimental to meeting our goals. This part of your brain is involved in helping you take initiative, in ensuring that you have a broad array of interests, in shifting your attention
away
from what’s comfortable and
toward
what you need to meet your objectives. It makes you feel distress when your actions don’t help you achieve your desired goals, so that you’ll modify your approach next time. It helps you connect similar experiences together even when they are very unfamiliar to you, so that you can learn from the experiences of others and not just your own. It helps you be flexible and adaptive. Animals such as rats don’t have prefrontal cortices that are as developed as ours. They respond to what’s right in front of them and are not as able to plan out complex actions as we are. Rats can’t decide they are gaining too much weight and then suppress the urge to eat that chocolate cake. They can’t think through their daily diet and decide something that they want doesn’t fit. You can do those things. In short, you need this complex part of your brain to make good decisions.

Unfortunately, this same part of your brain is also involved in cravings. A recent study proved this point rather dramatically when researchers were able to use rapid transcranial magnetic stimulation (the rTMS technique I described earlier) applied to the prefrontal cortex to temporarily reduce food cravings and improve the ability to resist cravings.
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More recent (and absolutely fascinating) research has shown that some relapses related to cues and context are mediated by a small subgroup of neurons in the medial prefrontal cortex. A cue or context might be watching a late night commercial for Ben and Jerry’s ice cream, for example, and then driving to the 7-Eleven to buy a pint. The researchers were able to inactivate these neurons and prevent context-induced heroin relapse in rats! Other research on humans with damage to this region of the brain suggests that this brain structure is responsible for helping people set an acceptable level of risk. So, some individuals might be willing to go grocery shopping when hungry, for example, because they believe that they are immune to the displays and smells of fattening, sugary foods. This research is extremely exciting because it suggests that the effects of cues and context on addictive behavior may be controlled by a small group of neurons in the prefrontal cortex, which could be a future target for therapies.
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When I first heard the story of Phineas Gage in medical school, I thought to myself, “What a lucky guy! He could have completely lost his vision, his motor function, or even his speech. He lost a significant chunk of his brain but managed to keep all the really important stuff and survive.” Over the years, as I’ve learned more about the brain and human behavior, I realized that Phineas actually lost the part of his brain he needed the most. He would likely have done much better with the rest of his life had he lost his vision, his ability to speak, or even his motor abilities.

You won’t hear about a case like Phineas’s very often; obviously it’s an extremely rare event to have a rod shoot through your skull, to survive, and to only lose a specific part of your brain, namely a part of the prefrontal cortex. Yet, in another respect, it’s happening every day and all around you. Addictions hijack this critical brain region, and people who suffer from addictions can have severely impaired prefrontal cortices. For many addicts, it would have been better if they had lost their ability to walk, hear, see, or even speak. People usually survive those other types of handicaps, which don’t produce the same type of devastation that the pandemic of addiction causes: devastated lives, broken homes, full prisons, advanced medical and psychiatric disease, suicides, and other causes of death. While the metaphor is crude, if addictive conditions weren’t so treatable, it might actually (in some cases) be better to have a rod shot through your head.

The Brain’s Punishment System

Now that we’ve learned a bit about the brain’s reward system, it’s time to look at another brain system—the system responsible for punishment. This system is made up of areas of the brain that are activated in response to fear and punishment, and sometimes this system can override the reward system and actually inhibit rewarding behaviors. Most of these brain regions lie in what scientists called the periventricular system (PVS). Finally, a third system, called the behavioral inhibition system (BIS), was discovered by the brilliant French physician Henri Laborit in the mid-1960s. The BIS is activated when motivation and reward are impossible, but so are avoidance and flight. At this point, the person can no longer experience reward but can also no longer run away from pain and punishment. It’s when a person has become chronically stressed and feels helpless to act that the BIS is most active. This system, which is heavily affected by the neurotransmitter serotonin, may be responsible for much of the misery that addicts experience when they cannot experience joy from the reward but are powerless to resist continuing their self-destructive actions. This is especially common as addiction progresses, and the result can be an overwhelming sense of helplessness.

In addition to the powerful brain mechanisms underlying reward and punishment that play a role in craving and addiction, there is also a complex relationship between emotions, memory, and craving. Emotions affect memory, and memories affect emotions. And both memory and emotions affect cravings. Furthermore, cravings themselves affect working memory, especially visuospatial memory, which is a type of memory that records what you see and your orientation to your environment. As examples, visuospatial memory helps you remember and estimate how high your living room ceiling is, or helps you remember how many ceiling fans are in your living room.

A study of ninety-six undergraduates who were craving chocolate showed a definite reduction in their ability to perform certain tasks that require visuospatial memory.
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In other words, craving actually affected what these students were capable of remembering. Many more studies have shown this type of relationship (in particular, anxiety has been shown to impair working memory, which is the type of memory at work when you are thinking about what you are remembering). The takeaway from these studies is that if you wait to take action until you have a craving, you are already behind the eight ball, because it may be harder to remember what to do. This is why, in later chapters, I emphasize that although there are helpful steps to take when you are craving, the ideal time to address your cravings is when you are
not
actively craving. The time to fix the roof is when it’s not raining.

Emotions can profoundly affect cravings. One fascinating study of smokers who had strokes in a part of the brain called the insular cortex (a part of the brain’s emotion-regulating limbic system) found that these individuals were much more likely to stop smoking than people who had other types of strokes.
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This suggests a critical role of the limbic system and emotions in causing tobacco cravings. In particular, stress can both increase cravings and make them much harder to resist. For example, one recent Yale University study showed that smokers under stress were significantly less able to resist their nicotine cravings.
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Other studies have shown that intense emotions can increase the frequency and intensity of cravings. This is particularly a catch-22 for people who suffer from addiction, because numerous studies also show that emotions are usually all over the map in the early days, weeks, and even months after people stop drinking.
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However, avoiding emotions is not the answer, as doing so makes recovery extremely difficult, if not impossible. Some research actually suggests that expressing emotions can diminish cravings; a recent British study of cocaine addicts in rehab, for example, showed that when addicts wrote down their emotions they had fewer cravings (and they were less likely to relapse).
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My personal experience treating addicts confirms this as well. When people suffer from depression, anxiety, anger and resentment, fear, stress, and grief and loss, their cravings occur more often and are more intense. Also, in my experience, when those emotions are most intense, cravings can be very difficult to resist. At these times, people often succumb to their cravings, which leads to more emotional problems. And, sadly, often the harder they try to resist, the worse the cravings. The solution is not to combat cravings but to outgrow them, and later you’ll see exactly how you can do that.

Your brain’s systems are much more complex than we have described here. As we’ll see in the
next chapter
, thoughts also affect cravings and cravings affect thoughts; this relationship forms the basis of cognitive theories of cravings. Furthermore, experiences affect not just the neurotransmitters released or the receptor densities, but also the very connections that neurons make (as we’ll review in
chapter 5
). This has particular importance on how behavioral changes affect cravings and addiction, and we’ll explore the impact of behaviors on cravings in
chapters 5
and
9
. The effects that activated receptors have inside nerve cells (on important cell functions such as second messenger systems, transcription modification, and changes in cellular structure and function) are also directly affected by our behaviors and experiences. These changes are important not only in craving, but also in the release from craving. For example, the prefrontal cortex projects glutamate-releasing neurons back to the nucleus accumbens, and (in my opinion) probably forms a key basis for the neurobiology of willingness,
²¹
spirituality, and recovery.

So now we know enough to answer the question “Is addiction a disease or a choice?” The answer is yes. Addiction is a disease
of
choice.

…

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