Sometimes, adolescents just can’t resist

Don’t get mad the next time you catch your teenager texting when he promised to be studying.

He simply may not be able to resist.

A University of Iowa study found teenagers are far more sensitive than adults to the immediate effect or reward of their behaviors. The findings may help explain, for example, why the initial rush of texting may be more enticing for adolescents than the long-term payoff of studying.

“The rewards have a strong, perceptional draw and are more enticing to the teenager,” says Jatin Vaidya, a professor of psychiatry at the UI and corresponding author of the study, which appeared online this week in the journal Psychological Science. “Even when a behavior is no longer in a teenager’s best interest to continue, they will because the effect of the reward is still there and lasts much longer in adolescents than in adults.”

For parents, that means limiting distractions so teenagers can make better choices. Take the homework and social media dilemma: At 9 p.m., shut off everything except a computer that has no access to Facebook or Twitter, the researchers advise.

“I’m not saying they shouldn’t be allowed access to technology,” Vaidya says. “But they need help in regulating their attention so they can develop those impulse-control skills.”

In their study, “Value-Driven Attentional Capture in Adolescence,” Vaidya and co-authors Shaun Vecera, a professor of psychology, and Zachary Roper, a graduate student in psychology, note researchers generally believe teenagers are impulsive, make bad decisions, and engage in risky behavior because the frontal lobes of their brains are not fully developed.

But the UI researchers wondered whether something more fundamental was going on with adolescents to trigger behaviors independent of higher-level reasoning.

“We wanted to try to understand the brain’s reward system and how it changes from childhood to adulthood,” says Vaidya, who adds the reward trait in the human brain is much more primitive than decision-making. “We’ve been trying to understand the reward process in adolescence and whether there is more to adolescent behavior than an under-developed frontal lobe,” he adds.

For their study, the researchers recruited 40 adolescents, ages 13 and 16, and 40 adults, ages 20 and 35. First, participants were asked to find a red or green ring hidden within an array of rings on a computer screen. Once identified, they reported whether the white line inside the ring was vertical or horizontal. If they were right, they received a reward between 2 and 10 cents, depending on the color. For some participants, the red ring paid the highest reward; for others, it was the green. None was told which color would pay the most.

After 240 trials, the participants were asked whether they noticed anything about the colors. Most made no association between a color and reward, which researchers say proves the ring exercise didn’t involve high-level, decision-making.

In the next stage, participants showed they had developed an intuitive association when they were asked to find a diamond-shaped target. This time, the red and green rings were used as decoys.

At first, the adolescents and adults selected the color ring that garnered them the highest monetary reward, the goal of the first trial. But in short order, the adults adjusted and selected the diamond. The adolescents did not.

Even after 240 trials, the adolescents were still more apt to pick the colored rings.

“Even though you’ve told them, ‘You have a new target,’ the adolescents can’t get rid of the association they learned before,” Vecera says. “It’s as if that association is much more potent for the adolescent than for the adult.

“If you give the adolescent a reward, it will persist longer,” he adds. “The fact that the reward is gone doesn’t matter. They will act as if the reward is still there.”

Researchers say that inability to readily adjust behavior explains why, for example, a teenager may continue to make inappropriate comments in class long after friends stopped laughing.

In the future, researchers hope to delve into the psychological and neurological aspects of their results.

“Are there certain brain regions or circuits that continue to develop from adolescence to adulthood that play role in directing attention away from reward stimuli that are not task relevant?” Vaidya asks. “Also, what sort of life experiences and skill help to improve performance on this task?”

(Image caption: This is the happiness equation, where t is the trial number, w0 is a constant term, other weights w capture the influence of different event types, 0 ≤ γ ≤ 1 is a forgetting factor that makes events in more recent trials more influential than those in earlier trials, CRj is the CR if chosen instead of a gamble on trial j, EVj is the EV of a gamble (average reward for the gamble) if chosen on trial j, and RPEj is the RPE on trial j contingent on choice of the gamble. The RPE is equal to the reward received minus the expectation in that trial EVj. If the CR was chosen, then EVj = 0 and RPEj = 0; if the gamble was chosen, then CRj = 0. The variables in the equation are quantities that the neuromodulator dopamine has been associated with in previous neuroscience studies. Credit: Robb Rutledge, UCL)

Equation to predict happiness

The happiness of over 18,000 people worldwide has been predicted by a mathematical equation developed by researchers at UCL, with results showing that moment-to-moment happiness reflects not just how well things are going, but whether things are going better than expected.

The new equation accurately predicts exactly how happy people will say they are from moment to moment based on recent events, such as the rewards they receive and the expectations they have during a decision-making task. Scientists found that overall wealth accumulated during the experiment was not a good predictor of happiness. Instead, moment-to-moment happiness depended on the recent history of rewards and expectations. These expectations depended, for example, on whether the available options could lead to good or bad outcomes.

The study, published in the Proceedings of the National Academy of Sciences, investigated the relationship between happiness and reward, and the neural processes that lead to feelings that are central to our conscious experience, such as happiness. Before now, it was known that life events affect an individual’s happiness but not exactly how happy people will be from moment to moment as they make decisions and receive outcomes resulting from those decisions, something the new equation can predict.

Scientists believe that quantifying subjective states mathematically could help doctors better understand mood disorders, by seeing how self-reported feelings fluctuate in response to events like small wins and losses in a smartphone game. A better understanding of how mood is determined by life events and circumstances, and how that differs in people suffering from mood disorders, will hopefully lead to more effective treatments.

Research examining how and why happiness changes from moment to moment in individuals could also assist governments who deploy population measures of wellbeing to inform policy, by providing quantitative insight into what the collected information means. This is especially relevant to the UK following the launch of the National Wellbeing Programme in 2010 and subsequent annual reports by the Office for National Statistics on ‘Measuring National Wellbeing’.

For the study, 26 subjects completed a decision-making task in which their choices led to monetary gains and losses, and they were repeatedly asked to answer the question ‘how happy are you right now?’. The participant’s neural activity was also measured during the task using functional MRI and from these data, scientists built a computational model in which self-reported happiness was related to recent rewards and expectations. The model was then tested on 18,420 participants in the game ‘What makes me happy?’ in a smartphone app developed at UCL called 'The Great Brain Experiment'. Scientists were surprised to find that the same equation could be used to predict how happy subjects would be while they played the smartphone game, even though subjects could win only points and not money.

Lead author of the study, Dr Robb Rutledge (UCL Wellcome Trust Centre for Neuroimaging and the new Max Planck UCL Centre for Computational Psychiatry and Ageing), said: “We expected to see that recent rewards would affect moment-to-moment happiness but were surprised to find just how important expectations are in determining happiness. In real-world situations, the rewards associated with life decisions such as starting a new job or getting married are often not realised for a long time, and our results suggest expectations related to these decisions, good and bad, have a big effect on happiness.

"Life is full of expectations - it would be difficult to make good decisions without knowing, for example, which restaurant you like better. It is often said that you will be happier if your expectations are lower. We find that there is some truth to this: lower expectations make it more likely that an outcome will exceed those expectations and have a positive impact on happiness. However, expectations also affect happiness even before we learn the outcome of a decision. If you have plans to meet a friend at your favourite restaurant, those positive expectations may increase your happiness as soon as you make the plan. The new equation captures these different effects of expectations and allows happiness to be predicted based on the combined effects of many past events.

"It’s great that the data from the large and varied population using The Great Brain Experiment smartphone app shows that the same happiness equation applies to thousands people worldwide playing our game, as with our much smaller laboratory-based experiments which demonstrate the tremendous value of this approach for studying human well-being on a large scale."

The team used functional MRI to demonstrate that neural signals during decisions and outcomes in the task in an area of the brain called the striatum can be used to predict changes in moment-to-moment happiness. The striatum has a lot of connections with dopamine neurons, and signals in this brain area are thought to depend at least partially on dopamine. These results raise the possibility that dopamine may play a role in determining happiness.

Overlapping Neural Systems Represent Cognitive Effort and Reward Anticipation

Anticipating a potential benefit and how difficult it will be to obtain it are valuable skills in a constantly changing environment. In the human brain, the anticipation of reward is encoded by the Anterior Cingulate Cortex (ACC) and Striatum. Naturally, potential rewards have an incentive quality, resulting in a motivational effect improving performance. Recently it has been proposed that an upcoming task requiring effort induces a similar anticipation mechanism as reward, relying on the same cortico-limbic network. However, this overlapping anticipatory activity for reward and effort has only been investigated in a perceptual task. Whether this generalizes to high-level cognitive tasks remains to be investigated. To this end, an fMRI experiment was designed to investigate anticipation of reward and effort in cognitive tasks. A mental arithmetic task was implemented, manipulating effort (difficulty), reward, and delay in reward delivery to control for temporal confounds. The goal was to test for the motivational effect induced by the expectation of bigger reward and higher effort. The results showed that the activation elicited by an upcoming difficult task overlapped with higher reward prospect in the ACC and in the striatum, thus highlighting a pivotal role of this circuit in sustaining motivated behavior.

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The motivation to move: Study finds rats calculate ‘average’ of reward across several tests

Suppose you had $1,000 to invest in the stock market. How would you decide to pick one stock over another? Scientists have made great progress in understanding the neuroscience behind how people choose between similar options.

But what happens when neither choice is right?

During an economic downturn, for instance, your best option might be not to invest at all, but to wait for market conditions to improve.

Using an unusual decision-making study, Harvard researchers exploring the question of motivation found that rats will perform a task faster or slower depending on the size of the benefit they receive, suggesting that they maintain a long-term estimate of whether it’s worth it to them to invest energy in a task.

As described in an April 14 paper in Nature Neuroscience, a research team led by Naoshige Uchida, associate professor of molecular and cellular biology, found that rats averaged how much benefit they received over as many as five trials. When their brains were impaired in one region, however, the rats based their actions solely on the prior trial.

“This is a new framework to think about decision-making,” Uchida said. “There have been many studies that focused on action selection or choices, but the question of the overall pace or rate of performance has been largely ignored.”

To get at those decision-making questions, Uchida and his team designed the experiment.

In each trial, rats were presented with an apparatus that had three holes. Based on whether a sweet or sour odor was delivered through the middle hole, rats went either left or right to receive a water reward. On one side they received a large reward; the other side delivered a smaller reward.

“What we measured was, after getting the reward, how quickly they went back to initiate the next trial,” Uchida said.

What researchers found, Uchida said, was surprising. When rats received, on average, a larger reward, they were more likely to quickly initiate the next trial, which suggested that they weren’t reacting merely to the prior result, but were “averaging the size of the reward from several previous trials.”

“They essentially calculate the average over the previous five or six trials, and adjust their performance accordingly,” Uchida said. “They’re making a calculation to determine whether they’re getting something out of the task or not. If it’s worth it for them, they go faster. If not, they go slower.”

When researchers impaired part of the striatum, a brain structure that is part of the basal ganglia and is thought to be involved with associative thinking, in the rats’ brains, however, that calculation changed. Rather than considering the average of multiple trials, the rats chose whether to go slower or faster based solely on the prior result.

“They still go faster or slower depending on the size of the reward, but they base that decision only on the size of the reward they just got,” Uchida said. “So the rat becomes very myopic. They only care about what just happened, and they don’t take other trials into account.”

In addition to shedding new light on how decision-making happens, the study may also offer some hope for people suffering from Parkinson’s disease.

“This part of the striatum receives a great deal of inputs from dopamine neurons, so it may be related to Parkinson’s disease,” Uchida said. “Some people now think Parkinson’s may actually be related to the motivation, or ‘vigor’ to perform some movement. So if we can identify brain regions that are involved in the regulation of general motivation, it’s possible that it could be contributing to the symptoms of Parkinson’s disease.”

Going forward, Uchida said, he hopes to study the role dopamine plays in regulating motivation and decision making, as well as working to understand what role other areas of the striatum might play in the process.

“There are some interesting similarities between this part of the striatum in rats and in humans,” he said. “One is that this area receives very heavy inputs from the prefrontal cortex. That’s an area that may be important in integrating information over a longer period of time. Deconstructing this process is a critical step to understanding our behavior, and this could go a long way toward that.”

Avoid impulsive acts by imagining future benefits

Why is it so hard for some people to resist the least little temptation, while others seem to possess incredible patience, passing up immediate gratification for a greater long-term good?

The answer, suggests a new brain imaging study from Washington University in St. Louis, lies in how effective people are at feeling good right now about all the future benefits that may come from passing up a smaller immediate reward. Researchers found that activity in two regions of the brain distinguished impulsive and patient people.

“Activity in one part of the brain, the anterior prefrontal cortex, seems to show whether you’re getting pleasure from thinking about the future reward you are about to receive,” explains study co-author Todd Braver, PhD, professor of psychology in Arts & Sciences. “People can relate to this idea that when you know something good is coming, just that waiting can feel pleasurable.”

The study, which was published in the first issue of the Journal of Neuroscience this year, was designed to examine what happens in the brain as people wait for a reward, especially whether people characterized as “impulsive” would show different brain responses than those considered “patient.”

The lead author of the study was Koji Jimura, then a postdoctoral researcher in Braver’s Cognitive Control and Psychopathology Laboratory, and now a research associate professor at the Tokyo Institute of Technology, in Japan.

Unlike previous research on delayed gratification that had people choose between hypothetical rewards of money over long delays (e.g, $500 now or $1,000 a year from now), this Washington University study presented their participants with real rewards of squirts of juice that they chose to receive either immediately or after a delay of up to a minute.

“It’s kind of funny because we treated the people in our study like researchers that work with animals do, and we actually squirted juice into their mouths,” Braver says.

Results show that a brain region called the ventral striatum (VS) ramped up its activity in impulsive people as they got closer and closer to receiving their delayed reward. The VS activity of patient people, on the other hand, stayed more constant.

The researchers interpreted these different brain responses to mean that impulsive people initially did not find the prospect of waiting for a reward very appealing. However, as they approached the time they’d receive that reward, they became more excited and their VS reflected that excitement.

“This gradual increase may reflect impatience or excessive anticipation of the upcoming reward in impulsive individuals,” says Jimura. This was unlike patient people, who were likely content with waiting for the reward from the start, as no changes in VS activity were observed for them.

The most novel finding of the study concerned the anterior prefrontal cortex (aPFC). This is the part of the brain that helps you think about the future. Here, we found that the patient people heightened activity in the aPFC when they first started waiting for they reward, which then decreased as the time to receive the reward approached. Impulsive people didn’t show this brain activity pattern.

“The aPFC appears to allow you to create a mental simulation of the future. It helps you consider what it’ll be like getting the future reward. In this way, you can get access to the utility and satisfaction in the present,” says Braver.

By thinking about the future reward, patient people were able to gain what economists call “anticipatory utility.” While their reward was far away in time, they were giddy with anticipation in the present. Conversely, impulsive people weren’t thinking beyond the present and so did not feel pleasure when they were told they had to wait. Their excitement built only as they got closer to receiving their reward.

Overall this study suggests that people may be impulsive because they do not or cannot imagine the future, so they prefer rewards right away. This research could be useful for assessing the effects of clinical treatments for impulsivity problems, which can lead to issues such as problem gambling and substance abuse disorders. A similar brain imaging approach as was used in the Washington University study could allow clinicians to track the effects of an intervention on changes not only in impulsive behavior but also changes in patients’ brain responses.

“One possible treatment approach could be to enhance mental functions in aPFC, a brain region well-known to be associated with cognitive control,” says Jimura. By increasing cognitive control, impulsive patients could learn to reject their immediate impulses.

Impulsivity occurs not only in a clinical setting but also every day in our own lives. Applying his research to his personal life, Braver says, “When I’m successful at achieving long-term goals it’s from explicitly trying to activate that goal and imagining each decision as helping me achieve it, to keep me on track.” Perhaps adopting this strategy of focusing on the long-term could help us move past present distractions and move toward our future goals.

Chimps solve puzzles for the thrill of it

A scientific explanation to why people perform better after receiving a compliment

A team of Japanese scientists have found scientific proof that people doing exercises appear to perform better when another person compliments them. The research was carried out by a group lead by National Institute for Physiological Sciences Professor Norihiro Sadato, Graduate University for Advanced Studies graduate student Sho Sugawara, Nagoya Institute of Technology Tenure-Track Associate Professor Satoshi Tanaka, and in collaboration with Research Center for Advanced Science and Technology Associate Professor Katsumi Watanabe. The team had previously discovered that the same area of the brain, the striatum, is activated when a person is rewarded a compliment or cash. Their latest research could suggest that when the striatum is activated, it seems to encourage the person to perform better during exercises. The paper is published online in PLOS ONE

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According to Professor Sadato, “To the brain, receiving a compliment is as much a social reward as being rewarded money. We’ve been able to find scientific proof that a person performs better when they receive a social reward after completing an exercise.  There seems to be scientific validity behind the message ‘praise to encourage improvement’. Complimenting someone could become an easy and effective strategy to use in the classroom and during rehabilitation.”

Morphine and cocaine affect reward sensation differently

A new study by scientists in the US has found that the opiate morphine and the stimulant cocaine act on the reward centers in the brain in different ways, contradicting previous theories that these types of drugs acted in the same way.

Morphine and cocaine both affect the flow of the neurotransmitter dopamine, which has been shown to be important in the feeling of reward. When a dopamine neuron is stimulated it releases dopamine, which is then taken up by neighboring cells. Any excess is reabsorbed into the original dopamine neuron by a process known as “reuptake.”

Cocaine is known to block reuptake, and the excess dopamine leads to an enhanced reward effect. Cocaine is also known to make the cells in the nucleus accumbens, which receives signals from the VTA, more sensitive to cocaine. It was already known a protein called brain-derived neurotrophic factor (BDNF) in the VTA region of the brain enhances the reward response to cocaine.

The new study shows that BDNF has the opposite effect when morphine is present, decreasing the reward response and the development of addiction rather than enhancing it. The researchers identified numerous genes regulated by BDNF and associated with its effects. They used genetic techniques to suppress BDNF, and then directly excited the neurons in the nucleus accumbens that normally receives transmitted impulses from the VTA.

They found that suppressing BDNF in the VTA allowed morphine to increase the excitability of dopamine neurons and hence enhance the reward. When they optically excited the dopamine terminals in the nucleus accumbens that normally receive the transmissions from the VTA, they also found a reversal in the normal effect of BDNF.