Healthy Brain, Happy Life (29 page)

BRAIN HACKS: PSYCHOLOGICAL STRESS REDUCTION

These Brain Hacks will help you reorient yourself in situations that you perceive as stressful.

•  Ask a friend you trust for suggestions on how to resolve your stressful situation.

•  Go out for drinks with friends and don’t think about your stressful situation at all for the whole night.

•  Ask someone directly involved in the situation how she thinks it should be resolved. Let that open the conversation.

•  Cultivate an attitude of optimism: if you don’t have the solution to the situation now, one will come along.

•  Seek out help from trusted supervisors, ombudsmen, therapists, or life coaches for solutions to big problems.

•  Don’t try to solve the issues all by yourself.

MAKING YOUR BRAIN SMILE:
Your Brain’s Reward System

A
s I did every typical weekday, I was standing on the subway platform about to board the number 6 train for work. But that day, I was not in a good mood. Why were there so many people on the platform? That woman just took the seat that I was headed for and didn’t even look up—I
hate
when that happens!

Wait a second, why was I so grouchy? Was I hungry? Nope. Was I sleep deprived? No again. I realized that I was in such a foul mood because I had been traveling and it had been five days since I had been able to exercise. That was it! I was craving my regular exercise.

Since getting hooked on exercise, my body and brain now protest when I don’t get my regular fix. As I explained in Chapter 4, we know exercise improves mood by increasing dopamine, serotonin, and endorphins in the brain. I look forward to that infusion of good mood, energy, power, and positivity that follows whenever I work out. The down side is that if I don’t get my typical dose (four to six workouts a week on average), I start to feel annoyed and edgy; it’s like something is bothering me that I can’t identify. I go through what feels like exercise withdrawal. This response is what is typically referred to as a healthy addiction—something beneficial to your physical or mental health that you always make time for despite all the other obligations in your life. These activities are highly valued and sorely missed if something prevents them from happening. Yes, I have a healthy addiction to exercise. I also have a healthy addiction to massages.

It turns out that there are a lot of things in life in addition to exercise and massages that bring me great pleasure. They include (not surprisingly) delicious food, fresh cold watermelon juice, tickets to Broadway shows, river rafting, watching
The Sound of Music
with popcorn and hot chocolate, a surprising new finding from my lab, puppies, and Bach’s solo cello suites (note that this list is illustrative, not comprehensive).

What is on your pleasure list? It turns out that every single item on my list has one characteristic in common. Each one activates the reward circuit in my brain. Our reward center is an evolutionarily ancient system that goes back two billion years and is crucial to our survival. Evolution has designed this system so that we find pleasure in those basic functions that allow us to survive and propagate: food, drink, and sex are central to that list. Rudimentary versions of this reward system are seen in worms and flies. These are called fundamental or core pleasures. But, of course, as living, breathing beings in a consumer-driven world we derive pleasure from a whole lot more than just food, drink, and sex. Our much more diverse list of pleasures is called higher-order pleasure. We derive delight from the people we love to spend time with; the places we go to relax and rejuvenate; and all that we spend money, effort, and time on.

Typically, what we value most in our lives can be found on these lists of pleasures. What’s important to understand is that all of the key life decisions and choices that either bring more pleasure in our lives or limit it are influenced strongly by our brain’s reward system. While one could argue that pleasure and happiness should be at the top of our wish list of things to understand about the brain, in reality only recently has serious effort been made to explore the neurobiology of pleasure and happiness. Fortunately or unfortunately, a lot of our current, nuanced understanding about the science of happiness, like a lot of neuroscience research, comes from studies of when this system is broken. In other words, we have learned the most about the brain’s reward and pleasure systems from studies of addiction. In this chapter, I describe what we know about how the brain processes rewarding information for both fundamental and higher-order pleasurable stimuli as well as what we have learned about the brain’s reward system from the study of addiction, including how exercise might help.

THE REWARD SYSTEM: A PRIMER

Before we get into the neurobiology of reward, it’s important to define what we mean by
reward
. Reward is not a single process but a network made up of three distinct components. The first component is the one we most associate with reward and that is the hedonic pleasure component or liking. The second component is wanting, defined as the motivation for reward. The third process is learning, which includes the associations, representations, and predictions about past rewards that anticipate future rewards. The learning part of reward is carried out by two brain areas that we have already talked about a lot: the hippocampus and the amygdala. As we learned in Chapter 2, the hippocampus is important for making new associations and the amygdala lays down emotional memories, including those associated with highly pleasurable experiences. This introduction gives us a hint of how complex, interdependent, and interconnected the hippocampus and amygdala are as they contribute to many different kinds of brain computations.

What about the brain areas associated with liking and wanting? Studies done way back in the 1960s at McGill University by James Olds and Peter Milner (former husband of Brenda Milner of H.M. fame) were the first to identify what they called the pleasure or reward centers in the brain. This duo was looking for areas in the rat brain that, when stimulated, would inhibit the rat from doing whatever was associated with the stimulation. But as they were stimulating different brain areas, they instead found the opposite: brain areas that, when stimulated, would get the rat to keep doing whatever he was doing when the stimulation occurred. They found that if they allowed the rats to stimulate the electrodes implanted in these special brain areas themselves (the so-called self-stimulation experiments), the rats would obsessively stimulate the electrodes thousands of times and would forgo food to continue self-stimulating. These experiments first identified some of the brain areas important for reward and pleasure. The basic reward circuit includes a key brain area involved in perceiving and responding to reward stimuli called the ventral tegmental area (VTA). The VTA is located in the middle of the brain and contains the neurons that make the most important neurotransmitter for the experience of reward or pleasure: dopamine. The VTA-based dopamine-making (or dopaminergic) cells project to two important areas in the reward circuit: the nucleus accumbens as well as parts of the prefrontal cortex.

While those early studies by Olds and Milner were interpreted as identifying the pleasure centers in the brain, later work questioned whether these were centers for pleasure (liking) or desire (wanting). Dopamine release from the VTA is implicated in both functions. In fact, most recent work in this area of neuroscience has made progress in developing tasks and approaches to differentiate liking from wanting and suggests that these two states seem to use different parts of the same reward circuit in the brain.

How do you know if a part of the brain is associated with pleasure? First, you have to define when a stimulus is pleasurable. In humans, it’s easy, you just ask them. In animals, scientists use a trick from Charles Darwin’s book. Darwin did a famous study on facial expressions and noted that all animals make facial gestures in response to the environment, and we now know that many of the gestures have been conserved across species, including facial responses to pleasurable food, also called the yummy face. If you have seen a baby eating food that she enjoys, you know immediately the face that I mean. It turns out that you can identify that same face in rodents and ask if stimulation to particular pleasure centers enhance the enjoyment of food (in particular sugary food) beyond how they would typically experience it. It was found that stimulation of two key brain areas enhanced a rat’s liking of sweets. The first is a particular part of the nucleus accumbens and the other is in the ventral pallidum, a structure located deep in the forebrain (toward the front of the brain). But these are not the only areas involved in pleasure. fMRI studies in humans have identified a wide range of cortical areas that are also activated during pleasurable experiences. These include a part of the prefrontal cortex called the orbitofrontal cortex, the medial portion of the prefrontal cortex, the cingulate cortex, and the insula (which is deeply buried in the sides of the brain between the temporal and frontal lobes). Other fMRI studies have shown that parts of the orbitofrontal cortex are activated whenever subjects report the sensation of pleasantness associated with chocolate milk. But once a lot of chocolate milk has been consumed, this area is no longer active and corresponds to a point when the person reports no more pleasure from the treat.

A key open question is whether these pleasure areas are involved in simply encoding pleasure or if they are involved in causing the sensation of pleasure. The jury is still out. These areas are clearly involved in encoding pleasure, but we are still working on understanding exactly how the actual feeling of pleasure is generated in the brain.

While pleasure (somewhat sadly) is relatively understudied, the other side of the coin of reward, want, is extremely well studied in the form of addiction. In fact, we have learned the most about the workings of this part of the reward system through the study of this disease.

ILLUSTRATION OF THE MAJOR BRAIN STRUCTURES INVOLVED IN THE REWARD CIRCUIT

(Courtesy of Ashley Halsey)