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Posts Tagged ‘motivation

Subconscious Signals Can Trigger Drug Craving

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Using a brain imaging technology called functional magnetic resonance imaging (fMRI), scientists have discovered that cocaine-related images trigger the emotional centers of the brains of patients addicted to drugs — even when the subjects are unaware they’ve seen anything.
Cocaine patients were shown photos such as these. The 24 randomly-presented 33 msec targets in each of four categories (cocaine, sexual, aversive and neutral, interspersed with grey-screen nulls) were immediately followed by a 467 msec neutral “masking” stimulus”. Under these conditions, the 33 msec stimuli can escape conscious detection. (Credit: Childress AR, Ehrman RN, Wang Z, Li Y, Sciortino N, et al.)

A team of researchers at the University of Pennsylvania, led by Dr. Anna Rose Childress and Dr. Charles O’Brien, showed cocaine patients photos of drug-related cues like crack pipes and chunks of cocaine. The images flashed by in just 33 milliseconds — so quickly that the patients were not consciously aware of seeing them. Nonetheless, the unseen images stimulated activity in the limbic system, a brain network involved in emotion and reward, which has been implicated in drug-seeking and craving.

“This is the first evidence that cues outside one’s awareness can trigger rapid activation of the circuits driving drug-seeking behavior,” said NIDA director Dr. Nora Volkow. “Patients often can’t pinpoint when or why they start craving drugs. Understanding how the brain initiates that overwhelming desire for drugs is essential to treating addiction.”

To verify that the patterns of brain activity triggered by the subconscious cues reflected the patients’ feelings about drugs, Childress and her colleagues gave the patients a different test two days later, allowing them to look longer at the drug images. The patients who demonstrated the strongest brain response to unseen cues in the fMRI experiment also felt the strongest positive association with visible drug cues. Childress notes, “It’s striking that the way people feel about these drug-related images is accurately predicted by how strongly their brains respond within just 33 milliseconds.”

Childress and her colleagues also found that the regions of the brain activated by drug images overlapped substantially with those activated by sexual images. This finding supports the scientific consensus that addictive drugs usurp brain regions that recognize natural rewards needed for survival, like food and sex.

According to Childress, these results could improve drug treatment strategies. “We have a brain hard-wired to appreciate rewards, and cocaine and other drugs of abuse latch onto this system. We are looking at the potential for new medications that reduce the brain’s sensitivity to these conditioned drug cues and would give patients a fighting chance to manage their urges.”

PLoS ONE 3(1): e1506. doi:10.1371/journal.pone.0001506

Prelude to Passion: Limbic Activation by “UnseenDrug and Sexual Cues

Anna Rose Childress, Ronald N. Ehrman, Ze Wang, Yin Li, Nathan Sciortino, Jonathan Hakun, William Jens, Jesse Suh, John Listerud, Kathleen Marquez, Teresa Franklin, Daniel Langleben, John Detre, Charles P. O’Brien

Abstract

Background

The human brain responds to recognizable signals for sex and for rewarding drugs of abuse by activation of limbic reward circuitry. Does the brain respond in similar way to such reward signals even when they are “unseen”, i.e., presented in a way that prevents their conscious recognition? Can the brain response to “unseen” reward cues predict the future affective response to recognizable versions of such cues, revealing a link between affective/motivational processes inside and outside awareness?

Methodology/Principal Findings

We exploited the fast temporal resolution of event-related functional magnetic resonance imaging (fMRI) to test the brain response to “unseen” (backward-masked) cocaine, sexual, aversive and neutral cues of 33 milliseconds duration in male cocaine patients (n = 22). Two days after scanning, the affective valence for visible versions of each cue type was determined using an affective bias (priming) task. We demonstrate, for the first time, limbic brain activation by “unseen” drug and sexual cues of only 33 msec duration. Importantly, increased activity in an large interconnected ventral pallidum/amygdala cluster to the “unseen” cocaine cues strongly predicted future positive affect to visible versions of the same cues in subsequent off-magnet testing, pointing both to the functional significance of the rapid brain response, and to shared brain substrates for appetitive motivation within and outside awareness.

Conclusions/Significance

These findings represent the first evidence that brain reward circuitry responds to drug and sexual cues presented outside awareness. The results underscore the sensitivity of the brain to “unseen” reward signals and may represent the brain’s primordial signature for desire. The limbic brain response to reward cues outside awareness may represent a potential vulnerability in disorders (e.g., the addictions) for whom poorly-controlled appetitive motivation is a central feature.

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Written by huehueteotl

February 6, 2008 at 9:37 am

Why Some People Can’t Handle Success

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… it’s about self-sabotage. New research shows that how people view their abilities in the workplace impacts how they respond to success. Dr. Jason Plaks, a social psychologist at the University of Toronto and Kristin Stecher, a research scientist at the University of Washington, found that those who thought of their capabilities as fixed were more likely to become anxious and disoriented when faced with dramatic success, causing their subsequent performance to plummet, compared to those who thought of their abilities as changeable.

success-in-sight-cycle.jpg

“People are driven to feel that they can predict and control their outcomes. So when their performance turns out to violate their predictions, this can be unnerving — even if the outcome is, objectively speaking, good news,” says Plaks. He points out that the notion that people often sacrifice their success in the name of greater certainty has some intuitive appeal but it has never been put to a rigorous test.

In one representative study, Plaks and Stecher used a questionnaire to classify participants into those who endorsed a fixed view of intelligence and those who endorsed a malleable view. Then participants took three versions of what was purported to be an intelligence test. After the first test, all participants were given a lesson on how to improve their score. After the second test, participants were randomly assigned to be told that their performance had improved, stayed constant, or declined.

Among those who believed they had improved, those with the fixed view became more anxious and performed worse on the third test than those with the malleable view. However, among participants who believed that their performance had failed to improve, it was the malleable view participants who grew anxious and underperformed compared to their fixed view counterparts.

Plaks notes that if people gain an understanding of how they view their abilities, as fixed or changeable, then they can be aware of the advantages and pitfalls of both perspectives. This in turn may better equip them to adopt alternative theories to explain life’s ups and downs. “Both approaches are highly intuitive and that makes them relatively easy to teach,” says Plaks. “If we can get people to change their underlying assumptions about their abilities then they may improve their performance and that is positive news for those charged with the task of getting people to reach their full potential.”

J Pers Soc Psychol. 2007 Oct;93(4):667-84.

Unexpected improvement, decline, and stasis: a prediction confidence perspective on achievement success and failure.

Plaks JE, Stecher K.

Department of Psychology, University of Toronto, Ontario, Canada. plaks@psych.utoronto.ca

The authors hypothesized that reactions to performance feedback depend on whether one’s lay theory of intelligence is supported or violated. In Study 1, following improvement feedback, all participants generally exhibited positive affect, but entity theorists (who believe that intelligence is fixed) displayed more anxiety and more effort to restore prediction confidence than did incremental theorists (who believe that intelligence is malleable). Similarly, when performance declined, entity theorists displayed more anxiety and compensatory effort than incremental theorists. However, when performance remained rigidly static despite a learning opportunity, incremental theorists evinced more anxiety and compensatory effort than entity theorists. In Study 2, this pattern was replicated when the entity and incremental theories were experimentally manipulated. Study 3 demonstrated that for both groups, theory violation impairs subsequent task performance. Taken together, these studies provide evidence that lay theory violation and damaged prediction confidence have significant and measurable effects on emotion and motivation. The authors discuss the implications of these findings for the literature on achievement success and failure. (PsycINFO Database Record (c) 2007 APA, all rights reserved).

Money Motivates — Especially When Your Colleague Gets Less

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Meanness rulez: the feelings an individual has on receiving his paycheque depend critically on how much his colleague earns. Hard evidence for this comes from an experiment conducted by economists and brain scientists at the University of Bonn. They tested male subjects in pairs, asking them to perform a simple task and promising payment for success. Using magnetic resonance tomographs, the researchers examined the volunteers’ brain activity throughout the activities.

Participants who got more money than their co-players showed much stronger activation in the brain’s “reward centre” than occurred when both players received the same amount.

The publication of these findings is the first outcome of a new line of research being established at Bonn University. A group of scholars around the epileptologist Professor Dr. Christian Elger and the economist Professor Dr. Armin Falk want to find out just how the mind of “Homo oeconomicus” works. To this end, they are using modern imaging techniques to look into the brains of their volunteers being tested in the lab.

In the experiment now published* the participants had to lie down next to each other in parallel brain scanners. They were asked to perform the same task simultaneously. Dots appeared on a screen and they had to estimate the number being displayed. They were then told whether their answer was correct. If they had solved the task correctly, they received a financial reward, which might range from 30 to 120 euros. Each participant also learnt how his partner in the game had performed and how much he would pocket in return.

Throughout this procedure the tomograph monitored the changes in blood circulation in the different regions of the subject’s brain. High blood flows indicate that the nerve cells in the respective part of the brain are particularly active. A total of 38 men took part in the experiment. “We registered enhanced activity in various parts of their brains during the test,” explains the Bonn neuroscientist Dr. Bernd Weber. “One area in particular, the ventral striatum, is the region where part of what we call the ‘reward system’ is located.”

The reward system is activated when an individual has an experience he considers worth aspiring to. “In this area we observed an activation when the player completed his task correctly,” says Bernd Weber, who heads the NeuroCognition Imaging group at the Life & Brain Institute. By contrast, when the subject got his estimate wrong, activity in his ventral striatum would subside. For us, however, the exciting finding here was the role played by another factor: the performance of the player in the other scanner. Weber’s colleague Dr. Klaus Fliessbach sums up the outcome, “Activation was at its highest for those players who got the right answer while their co-player got it wrong.”

The researchers then took a closer look at those cases in which both players estimated the number of points correctly. If the participants received the same payment there was relatively moderate activation of the reward centre. But if player one was given, say, 120 euros, while his partner received only 60, the activation turned out to be much stronger for player one. For player two, on the other hand, the blood flow into the ventral striatum actually decreased — even though he had performed the task successfully and had been rewarded for his efforts.

Men like competing

“This result clearly contradicts traditional economic theory,” explains Bonn-based economist Professor Dr. Armin Falk. “The theory assumes that the only important factor is the absolute size of the reward. The comparison with other people’s rewards shouldn’t really play any role in economic motivation.” It is the first time that this hypothesis has been challenged using such an experimental approach. It does not mean, of course, that the absolute size of the reward has no impact on the “reward centre”: more excitement was registered in response to 60 euros than 30. “But the interesting point to emerge from our study is that the relative size of one’s earnings plays such a major role,” Armin Falk insists.

“Men, at least, do appear to draw a great deal of their motivation from competition,” Dr. Bernd Weber concludes. The researchers now want to find out if that goes for women, too. Moreover, the team are planning a series of experiments with Asian subjects to see how far competitive thinking may be influenced by cultural factors.

Science 23 November 2007: Vol. 318. no. 5854, pp. 1305 – 1308 DOI: 0.1126/science.1145876

Social Comparison Affects Reward-Related Brain Activity in the Human Ventral Striatum
K. Fliessbach,1 B. Weber,1 P. Trautner,1 T. Dohmen,2 U. Sunde,2 C. E. Elger,1 A. Falk3*

Whether social comparison affects individual well-being is of central importance for understanding behavior in any social environment. Traditional economic theories focus on the role of absolute rewards, whereas behavioral evidence suggests that social comparisons influence well-being and decisions. We investigated the impact of social comparisons on reward-related brain activity using functional magnetic resonance imaging (fMRI). While being scanned in two adjacent MRI scanners, pairs of subjects had to simultaneously perform a simple estimation task that entailed monetary rewards for correct answers. We show that a variation in the comparison subject’s payment affects blood oxygenation level–dependent responses in the ventral striatum. Our results provide neurophysiological evidence for the importance of social comparison on reward processing in the human brain.

1 Life and Brain Center Bonn, Department of NeuroCognition and Clinic of Epileptology, Bonn, Germany.
2 Institute for the Study of Labor, Bonn, Germany.
3 University of Bonn, Department of Economics, Bonn, Germany.

* To whom correspondence should be addressed. E-mail: armin.falk@uni-bonn.de

Written by huehueteotl

November 23, 2007 at 2:33 pm