Lab Report is The Argus’ new, semi-regular column focusing on the research and activities of the Wesleyan University science community.
You may think that wanting and liking are the same—and they often are. We want what we like and we like what we want. But what happens in addiction?
Assistant Professor of Psychology and Neuroscience & Behavior Mike Robinson operates a fledgling lab that studies addiction from the “garden floor” of Judd Hall. Carrying over work that fascinated him as a graduate student at McGill University and as a postdoc at Michigan University, Robinson studies how desirable objects such as drugs, junk food, and slot machines abuse our natural reward systems and cause addiction.
“[Most of us] tend to have an array of rewards in our lives that keep us somewhat balanced,” Robinson said. “We care about time with our family and friends…. We like going to the movies. We like going for exercise…. One of the hallmarks of addictive behavior is when that balance becomes unstable and excessively focused onto one type of behavior.”
Drug use, in the form of anything from psychoactive drugs to Oreos, gives rise to addiction when motivation for that drug trumps motivation for all other rewards, leading to a severe lapse in lifestyle.
Robinson’s recent paper, entitled “Optogenetic Excitation of Central Amygdala Amplifies and Narrows Incentive Motivation to Pursue One Reward Above Another,” demonstrates how stimulation of a brain area called the central amygdala in rats leads them to focus excessively on one reward over another comparable reward. The study employed optogenetics, a technique that basically involves shooting lasers into rats’ brains to control a targeted brain area with light.
“We think that [the central amygdala] is one of the pathways that is excessively excited and over-stimulated during the development of addiction,” Robinson said.
So how does that relate to wanting and liking? Robinson discovered that although the rats were willing to work more than twice as hard for the substance to which they were addicted, they did not enjoy it more. The rats, observed through a glass floor, did not exhibit increased hedonic reactions that indicate enjoyment of the food. Stimulation of the central amygdala increases desire, but not enjoyment. While wanting and liking are usually coupled in healthy individuals, the brain processes wanting and liking in related, yet different, networks.
“There are several instances where wanting can become hyperactive and hypersensitive, and liking can become reduced,” Robinson said. “That is typically what we see in drug addiction where repeated drug taking causes less and less pleasure from the drug but more and more wanting of the drug.”
The uncoupling of wanting and liking underlies other addictive behaviors such as eating and gambling. Rats in Robinson’s lab that are fed high-fat and high-sugar diets lose sensitivity to these rewards and seek more. They continue to desire these foods at higher and higher levels, but their enjoyment decreases with the loss of sensitivity.
Robinson also studies how the brain becomes addicted to gambling. Unlike heroin or Doritos, which directly change the chemistry of the brain and body, gambling is an exterior condition. As for how gambling causes neuronal addiction, Robinson believes that uncertainty is the key to gambling addiction.
“Our brains are wired to want to resolve uncertainty because that increases fitness—to be able to know where rewards are coming from, what to avoid, [and] to learn the logic of our system,” Robinson said. “When certainty gets irresolvable like it [does] in a slot machine, then you have people constantly trying to understand what they can’t.”
Uncertainty is what makes a game fun. Robinson provided the example of tic-tac-toe: Children enjoy tic-tac-toe only because they do not yet know how to win; playing involves uncertainty. When they master the game and know how it will end, it is no longer fun to play. Similarly, when rats in Robinson’s lab face greater uncertainty in both the frequency and the payout of a reward, they are more motivated and will work harder. This helps to explain why the uncertainty of slot machines is so addictive.
The neuronal pathways involved in addiction—wanting and liking—are mostly sub-cortical, meaning they are ancient and often subconscious. Many addicts want to stop, but something more powerful than their conscious decisions take the wheel. Robinson hesitates to blame addicts who have had their natural reward systems hijacked. He believes that casinos and industries that produce junk food to profit from its increased palatability and cravability are partially at fault, and worries about widespread, constant access to addictive foods and gambling.
“Video games [and] the apps we have on our phones are using the same sort of approach,” Robinson warned. “They’re trying to use the same aspects of uncertainty that drive us to slot machines and putting them directly into our hands.”
Psychology is not an isolated mode of inquiry, but a way of improving human lives.
“Our society has gotten to the point where we need to consider the social ramifications,” Robinson said, referring to the high-reward products that are so freely available.
But we as individuals can take matters into our own hands, especially once we understand that most addicts do not love their drug of choice; they crave it. So next time you feel compelled to binge on a fatty snack or reach for another beer, ask yourself: Do you really like what you want?