Research & Scholarship
Current Research and Scholarly Interests
My lab and I seek to elucidate the neural basis of emotion (affective neuroscience), and explore implications for decision-making (neuroeconomics) and psychopathology (neurophenomics).
- Affective Neuroscience
PSYCH 251 (Spr)
- Amines and Affect
PSYCH 16N (Win)
- Brain and Decision Making
PSYCH 232 (Spr)
Independent Studies (12)
- Directed Individual Study in Environment and Resources
ENVRES 398 (Aut, Spr, Sum)
- Directed Reading in Neurosciences
NEPR 299 (Aut, Win, Spr, Sum)
- Directed Research in Environment and Resources
ENVRES 399 (Aut, Win, Spr, Sum)
- Graduate Research
NEPR 399 (Aut, Win, Spr, Sum)
- Graduate Research
PSYCH 275 (Aut, Win, Spr, Sum)
- Master's Degree Project
SYMSYS 290 (Win, Spr)
- Out-of-Department Advanced Research Laboratory in Experimental Biology
BIO 199X (Aut, Win, Spr, Sum)
- Ph.D. Qualifying Tutorial
ENVRES 410 (Spr)
- Practicum in Teaching
PSYCH 281 (Aut, Win, Spr)
- Reading and Special Work
PSYCH 194 (Aut, Win, Spr, Sum)
- Senior Honors Tutorial
SYMSYS 190 (Spr)
- Special Laboratory Projects
PSYCH 195 (Aut, Win, Spr, Sum)
- Directed Individual Study in Environment and Resources
Prior Year Courses
- Affective Neuroscience
PSYCH 251 (Spr)
- Amines and Affect
PSYCH 16N (Win)
- Brain and Decision Making
PSYCH 232 (Spr)
- Affective Neuroscience
PSYCH 251 (Spr)
- Brain and Decision Making
PSYCH 232 (Spr)
- Introduction to Psychology
PSYCH 1 (Win)
- Practicum in Teaching PSYCH 1
PSYCH 282 (Win)
- Affective Neuroscience
Graduate and Fellowship Programs
Adult age differences in frontostriatal representation of prediction error but not reward outcome.
Cognitive, affective & behavioral neuroscience
2014; 14 (2): 672-682
Emerging evidence from decision neuroscience suggests that although younger and older adults show similar frontostriatal representations of reward magnitude, older adults often show deficits in feedback-driven reinforcement learning. In the present study, healthy adults completed reward-based tasks that did or did not depend on probabilistic learning, while undergoing functional neuroimaging. We observed reductions in the frontostriatal representation of prediction errors during probabilistic learning in older adults. In contrast, we found evidence for stability across adulthood in the representation of reward outcome in a task that did not require learning. Together, the results identify changes across adulthood in the dynamic coding of relational representations of feedback, in spite of preserved reward sensitivity in old age. Overall, the results suggest that the neural representation of prediction error, but not reward outcome, is reduced in old age. These findings reveal a potential dissociation between cognition and motivation with age and identify a potential mechanism for explaining changes in learning-dependent decision making in old adulthood.
View details for DOI 10.3758/s13415-014-0297-4
View details for PubMedID 24853269
- Adult age differences in frontostriatal representation of prediction error but not reward outcome COGNITIVE AFFECTIVE & BEHAVIORAL NEUROSCIENCE 2014; 14 (2): 672-682
Affective traits link to reliable neural markers of incwentive anticipation
2014; 84: 279-289
While theorists have speculated that different affective traits are linked to reliable brain activity during anticipation of gains and losses, few have directly tested this prediction. We examined these associations in a community sample of healthy human adults (n=52) as they played a Monetary Incentive Delay task while undergoing functional magnetic resonance imaging (FMRI). Factor analysis of personality measures revealed that subjects independently varied in trait Positive Arousal and trait Negative Arousal. In a subsample (n=14) retested over 2.5years later, left nucleus accumbens (NAcc) activity during anticipation of large gains (+$5.00) and right anterior insula activity during anticipation of large losses (-$5.00) showed significant test-retest reliability (intraclass correlations>0.50, p's<0.01). In the full sample (n=52), trait Positive Arousal correlated with individual differences in left NAcc activity during anticipation of large gains, while trait Negative Arousal correlated with individual differences in right anterior insula activity during anticipation of large losses. Associations of affective traits with neural activity were not attributable to the influence of other potential confounds (including sex, age, wealth, and motion). Together, these results demonstrate selective links between distinct affective traits and reliably-elicited activity in neural circuits associated with anticipation of gain versus loss. The findings thus reveal neural markers for affective dimensions of healthy personality, and potentially for related psychiatric symptoms.
View details for DOI 10.1016/J.neuroimage.2013.08.055
View details for Web of Science ID 000328868600026
View details for PubMedID 24001457
Interpretable whole-brain prediction analysis with GraphNet
2013; 72: 304-321
Multivariate machine learning methods are increasingly used to analyze neuroimaging data, often replacing more traditional "mass univariate" techniques that fit data one voxel at a time. In the functional magnetic resonance imaging (fMRI) literature, this has led to broad application of "off-the-shelf" classification and regression methods. These generic approaches allow investigators to use ready-made algorithms to accurately decode perceptual, cognitive, or behavioral states from distributed patterns of neural activity. However, when applied to correlated whole-brain fMRI data these methods suffer from coefficient instability, are sensitive to outliers, and yield dense solutions that are hard to interpret without arbitrary thresholding. Here, we develop variants of the Graph-constrained Elastic-Net (GraphNet), a fast, whole-brain regression and classification method developed for spatially and temporally correlated data that automatically yields interpretable coefficient maps (Grosenick et al., 2009b). GraphNet methods yield sparse but structured solutions by combining structured graph constraints (based on knowledge about coefficient smoothness or connectivity) with a global sparsity-inducing prior that automatically selects important variables. Because GraphNet methods can efficiently fit regression or classification models to whole-brain, multiple time-point data sets and enhance classification accuracy relative to volume-of-interest (VOI) approaches, they eliminate the need for inherently biased VOI analyses and allow whole-brain fitting without the multiple comparison problems that plague mass univariate and roaming VOI ("searchlight") methods. As fMRI data are unlikely to be normally distributed, we (1) extend GraphNet to include robust loss functions that confer insensitivity to outliers, (2) equip them with "adaptive" penalties that asymptotically guarantee correct variable selection, and (3) develop a novel sparse structured Support Vector GraphNet classifier (SVGN). When applied to previously published data (Knutson et al., 2007), these efficient whole-brain methods significantly improved classification accuracy over previously reported VOI-based analyses on the same data (Grosenick et al., 2008; Knutson et al., 2007) while discovering task-related regions not documented in the original VOI approach. Critically, GraphNet estimates fit to the Knutson et al. (2007) data generalize well to out-of-sample data collected more than three years later on the same task but with different subjects and stimuli (Karmarkar et al., submitted for publication). By enabling robust and efficient selection of important voxels from whole-brain data taken over multiple time points (>100,000 "features"), these methods enable data-driven selection of brain areas that accurately predict single-trial behavior within and across individuals.
View details for DOI 10.1016/j.neuroimage.2012.12.062
View details for Web of Science ID 000317166800030
View details for PubMedID 23298747
- Spatial smoothing systematically biases the localization of reward-related brain activity NEUROIMAGE 2013; 66: 270-277
Serotonergic Genotypes, Neuroticism, and Financial Choices
2013; 8 (1)
Life financial outcomes carry a significant heritable component, but the mechanisms by which genes influence financial choices remain unclear. Focusing on a polymorphism in the promoter region of the serotonin transporter gene (5-HTTLPR), we found that individuals possessing the short allele of this gene invested less in equities, were less engaged in actively making investment decisions, and had fewer credit lines. Short allele carriers also showed higher levels of the personality trait neuroticism, despite not differing from others with respect to cognitive skills, education, or wealth. Mediation analysis suggested that the presence of the 5-HTTLPR short allele decreased real life measures of financial risk taking through its influence on neuroticism. These findings show that 5-HTTLPR short allele carriers avoid risky and complex financial choices due to negative emotional reactions, and have implications for understanding and managing individual differences in financial choice.
View details for DOI 10.1371/journal.pone.0054632
View details for Web of Science ID 000315563800059
View details for PubMedID 23382929
Frontostriatal White Matter Integrity Mediates Adult Age Differences in Probabilistic Reward Learning
JOURNAL OF NEUROSCIENCE
2012; 32 (15): 5333-5337
Frontostriatal circuits have been implicated in reward learning, and emerging findings suggest that frontal white matter structural integrity and probabilistic reward learning are reduced in older age. This cross-sectional study examined whether age differences in frontostriatal white matter integrity could account for age differences in reward learning in a community life span sample of human adults. By combining diffusion tensor imaging with a probabilistic reward learning task, we found that older age was associated with decreased reward learning and decreased white matter integrity in specific pathways running from the thalamus to the medial prefrontal cortex and from the medial prefrontal cortex to the ventral striatum. Further, white matter integrity in these thalamocorticostriatal paths could statistically account for age differences in learning. These findings suggest that the integrity of frontostriatal white matter pathways critically supports reward learning. The findings also raise the possibility that interventions that bolster frontostriatal integrity might improve reward learning and decision making.
View details for DOI 10.1523/JNEUROSCI.5756-11.2012
View details for Web of Science ID 000302793500031
View details for PubMedID 22496578
Spatial smoothing systematically biases the localization of reward-related brain activity.
2012; 66C: 270-277
Neuroimaging methods with enhanced spatial resolution such as functional magnetic resonance imaging (FMRI) suggest that the subcortical striatum plays a critical role in human reward processing. Analysis of FMRI data requires several preprocessing steps, some of which entail tradeoffs. For instance, while spatial smoothing can enhance statistical power, it may also bias localization towards regions that contain more gray than white matter. In a meta-analysis and reanalysis of an existing dataset, we sought to determine whether spatial smoothing could systematically bias the spatial localization of foci related to reward anticipation in the nucleus accumbens (NAcc). An activation likelihood estimate (ALE) meta-analysis revealed that peak ventral striatal ALE foci for studies that used smaller spatial smoothing kernels (i.e. <6mm FWHM) were more anterior than those identified for studies that used larger kernels (i.e. >7mm FWHM). Additionally, subtraction analysis of findings for studies that used smaller versus larger smoothing kernels revealed a significant cluster of differential activity in the left relatively anterior NAcc (Talairach coordinates: -10, 9, -1). A second meta-analysis revealed that larger smoothing kernels were correlated with more posterior localizations of NAcc activation foci (p<0.015), but revealed no significant associations with other potentially relevant parameters (including voxel volume, magnet strength, and publication date). Finally, repeated analysis of a representative dataset processed at different smoothing kernels (i.e., 0-12mm) also indicated that smoothing systematically yielded more posterior activation foci in the NAcc (p<0.005). Taken together, these findings indicate that spatial smoothing can systematically bias the spatial localization of striatal activity. These findings have implications both for historical interpretation of past findings related to reward processing and for the analysis of future studies.
View details for PubMedID 23110886
Toward an affective neuroscience account of financial risk taking.
Frontiers in neuroscience
2012; 6: 159-?
To explain human financial risk taking, economic, and finance theories typically refer to the mathematical properties of financial options, whereas psychological theories have emphasized the influence of emotion and cognition on choice. From a neuroscience perspective, choice emanates from a dynamic multicomponential process. Recent technological advances in neuroimaging have made it possible for researchers to separately visualize perceptual input, intermediate processing, and motor output. An affective neuroscience account of financial risk taking thus might illuminate affective mediators that bridge the gap between statistical input and choice output. To test this hypothesis, we conducted a quantitative meta-analysis (via activation likelihood estimate or ALE) of functional magnetic resonance imaging experiments that focused on neural responses to financial options with varying statistical moments (i.e., mean, variance, skewness). Results suggested that different statistical moments elicit both common and distinct patterns of neural activity. Across studies, high versus low mean had the highest probability of increasing ventral striatal activity, but high versus low variance had the highest probability of increasing anterior insula activity. Further, high versus low skewness had the highest probability of increasing ventral striatal activity. Since ventral striatal activity has been associated with positive aroused affect (e.g., excitement), whereas anterior insular activity has been associated with negative aroused affect (e.g., anxiety) or general arousal, these findings are consistent with the notion that statistical input influences choice output by eliciting anticipatory affect. The findings also imply that neural activity can be used to predict financial risk taking - both when it conforms to and violates traditional models of choice.
View details for DOI 10.3389/fnins.2012.00159
View details for PubMedID 23129993
Gain and Loss Learning Differentially Contribute to Life Financial Outcomes
2011; 6 (9)
Emerging findings imply that distinct neurobehavioral systems process gains and losses. This study investigated whether individual differences in gain learning and loss learning might contribute to different life financial outcomes (i.e., assets versus debt). In a community sample of healthy adults (n?=?75), rapid learners had smaller debt-to-asset ratios overall. More specific analyses, however, revealed that those who learned rapidly about gains had more assets, while those who learned rapidly about losses had less debt. These distinct associations remained strong even after controlling for potential cognitive (e.g., intelligence, memory, and risk preferences) and socioeconomic (e.g., age, sex, ethnicity, income, education) confounds. Self-reported measures of assets and debt were additionally validated with credit report data in a subset of subjects. These findings support the notion that different gain and loss learning systems may exert a cumulative influence on distinct life financial outcomes.
View details for DOI 10.1371/journal.pone.0024390
View details for Web of Science ID 000294689200041
View details for PubMedID 21915320
- The Influence of Affect on Beliefs, Preferences, and Financial Decisions JOURNAL OF FINANCIAL AND QUANTITATIVE ANALYSIS 2011; 46 (3): 605-626
Expected value information improves financial risk taking across the adult life span
SOCIAL COGNITIVE AND AFFECTIVE NEUROSCIENCE
2011; 6 (2): 207-217
When making decisions, individuals must often compensate for cognitive limitations, particularly in the face of advanced age. Recent findings suggest that age-related variability in striatal activity may increase financial risk-taking mistakes in older adults. In two studies, we sought to further characterize neural contributions to optimal financial risk taking and to determine whether decision aids could improve financial risk taking. In Study 1, neuroimaging analyses revealed that individuals whose mesolimbic activation correlated with the expected value estimates of a rational actor made more optimal financial decisions. In Study 2, presentation of expected value information improved decision making in both younger and older adults, but the addition of a distracting secondary task had little impact on decision quality. Remarkably, provision of expected value information improved the performance of older adults to match that of younger adults at baseline. These findings are consistent with the notion that mesolimbic circuits play a critical role in optimal choice, and imply that providing simplified information about expected value may improve financial risk taking across the adult life span.
View details for DOI 10.1093/scan/nsq043
View details for Web of Science ID 000291543100006
View details for PubMedID 20501485
The Affective Impact of Financial Skewness on Neural Activity and Choice
2011; 6 (2)
Few finance theories consider the influence of "skewness" (or large and asymmetric but unlikely outcomes) on financial choice. We investigated the impact of skewed gambles on subjects' neural activity, self-reported affective responses, and subsequent preferences using functional magnetic resonance imaging (FMRI). Neurally, skewed gambles elicited more anterior insula activation than symmetric gambles equated for expected value and variance, and positively skewed gambles also specifically elicited more nucleus accumbens (NAcc) activation than negatively skewed gambles. Affectively, positively skewed gambles elicited more positive arousal and negatively skewed gambles elicited more negative arousal than symmetric gambles equated for expected value and variance. Subjects also preferred positively skewed gambles more, but negatively skewed gambles less than symmetric gambles of equal expected value. Individual differences in both NAcc activity and positive arousal predicted preferences for positively skewed gambles. These findings support an anticipatory affect account in which statistical properties of gambles--including skewness--can influence neural activity, affective responses, and ultimately, choice.
View details for DOI 10.1371/journal.pone.0016838
View details for Web of Science ID 000287369200010
View details for PubMedID 21347239
When Giving Is Good: Ventromedial Prefrontal Cortex Activation for Others' Intentions
2010; 67 (3): 511-521
In social decision-making, people care both about others' outcomes and their intentions to help or harm. How the brain integrates representations of others' intentions with their outcomes, however, is unknown. In this study, participants inferred others' decisions in an economic game during functional magnetic resonance imaging. When the game was described in terms of donations, ventromedial prefrontal cortex (VMPFC) activation increased for inferring generous play and decreased for inferring selfish play. When the game was described in terms of individual savings, however, VMPFC activation did not distinguish between strategies. Distinct medial prefrontal regions also encoded consistency with situational norms. A separate network, including right temporoparietal junction and parahippocampal gyrus, was more activated for inferential errors in the donation than in the savings condition. These results demonstrate that neural responses to others' generosity or selfishness depend not only on their actions but also on their perceived intentions.
View details for DOI 10.1016/j.neuron.2010.06.030
View details for Web of Science ID 000280942900017
View details for PubMedID 20696386
Variability in Nucleus Accumbens Activity Mediates Age-Related Suboptimal Financial Risk Taking
JOURNAL OF NEUROSCIENCE
2010; 30 (4): 1426-1434
As human life expectancy continues to rise, financial decisions of aging investors may have an increasing impact on the global economy. In this study, we examined age differences in financial decisions across the adult life span by combining functional neuroimaging with a dynamic financial investment task. During the task, older adults made more suboptimal choices than younger adults when choosing risky assets. This age-related effect was mediated by a neural measure of temporal variability in nucleus accumbens activity. These findings reveal a novel neural mechanism by which aging may disrupt rational financial choice.
View details for DOI 10.1523/JNEUROSCI.4902-09.2010
View details for Web of Science ID 000274050000024
View details for PubMedID 20107069
Available alternative incentives modulate anticipatory nucleus accumbens activation
SOCIAL COGNITIVE AND AFFECTIVE NEUROSCIENCE
2009; 4 (4): 409-416
A reward or punishment can seem better or worse depending on what else might have happened. Little is known, however, about how neural representations of an anticipated incentive might be influenced by the available alternatives. We used event-related FMRI to investigate the activation in the nucleus accumbens (NAcc), while we varied the available alternative incentives in a monetary incentive delay task. Some task blocks included only uncertain gains and losses; others included the same uncertain gains and losses intermixed with certain gains and losses. The availability of certain gains and losses increased NAcc activation for uncertain losses and decreased the difference between uncertain gains and losses. We suggest that this pattern of activation can result from reference point changes across blocks, and that the worst available loss may serve as an important anchor for NAcc activation. These findings imply that NAcc activation represents anticipated incentive value relative to the current context of available alternative gains and losses.
View details for DOI 10.1093/scan/nsp031
View details for Web of Science ID 000273231000010
View details for PubMedID 19843618
Correction. "Affect dynamics, affective forecasting, and aging".
2009; 9 (5): ii-?
Reports an error in "Affect dynamics, affective forecasting, and aging" by Lisbeth Nielsen, Brian Knutson and Laura L. Carstensen (Emotion, 2008[Jun], Vol 8, 318-330). The first author of the article was listed as being affiliated with both the National Institute on Aging and the Department of Psychology, Stanford University. Dr. Nielsen would like to clarify that the research for this article was conducted while she was a postdoctoral fellow at Stanford University; her current affiliation is only with the National Institute on Aging. The copyright notice should also have been listed as "In the Public Domain." (The following abstract of the original article appeared in record 2008-06717-002.) [Correction Notice: The same erratum for this article was reported in Vol 8(5) of Emotion (see record 2008-13989-013).] Affective forecasting, experienced affect, and recalled affect were compared in younger and older adults during a task in which participants worked to win and avoid losing small monetary sums. Dynamic changes in affect were measured along valence and arousal dimensions, with probes during both anticipatory and consummatory task phases. Older and younger adults displayed distinct patterns of affect dynamics. Younger adults reported increased negative arousal during loss anticipation and positive arousal during gain anticipation. In contrast, older adults reported increased positive arousal during gain anticipation but showed no increase in negative arousal on trials involving loss anticipation. Additionally, younger adults reported large increases in valence after avoiding an anticipated loss, but older adults did not. Younger, but not older, adults exhibited forecasting errors on the arousal dimension, underestimating increases in arousal during anticipation of gains and losses and overestimating increases in arousal in response to gain outcomes. Overall, the findings are consistent with a growing literature suggesting that older people experience less negative emotion than their younger counterparts and further suggest that they may better predict dynamic changes in affect.
View details for DOI 10.1037/a0015739
View details for PubMedID 19803581
Don't stop thinking about tomorrow: Individual differences in future self-continuity account for saving
JUDGMENT AND DECISION MAKING
2009; 4 (4): 280-286
Some people find it more difficult to delay rewards than others. In three experiments, we tested a "future self-continuity" hypothesis that individual differences in the perception of one's present self as continuous with a future self would be associated with measures of saving in the laboratory and everyday life. Higher future self-continuity (assessed by a novel index) predicted reduced discounting of future rewards in a laboratory task, more matches in adjectival descriptions of present and future selves, and greater lifetime accumulation of financial assets (even after controlling for age and education). In addition to demonstrating the reliability and validity of the future self-continuity index, these findings are consistent with the notion that increased future self-continuity might promote saving for the future.
View details for Web of Science ID 000267218800003
Dissociable neural representations of future reward magnitude and delay during temporal discounting
2009; 45 (1): 143-150
In temporal discounting, individuals often prefer smaller immediate rewards to larger delayed rewards, implying a trade off between the magnitude and delay of future rewards. While recent functional magnetic resonance imaging (fMRI) investigations of temporal discounting have generated conflicting findings, no studies have focused on whether distinct neural substrates respond to the magnitude and delay of future rewards. Combining a novel, temporally distributed discounting task with event-related fMRI, we found that while nucleus accumbens (NAcc), mesial prefrontal cortical (MPFC), and posterior cingulate cortical (PCC) activation positively correlated with future reward magnitude, dorsolateral prefrontal cortical (DLPFC) and posterior parietal cortical (PPC) activation negatively correlated with future reward delay. Further, more impulsive individuals showed diminished NAcc activation to the magnitude of future rewards and greater deactivations to delays of future rewards in the MPFC, DLPFC, and PPC. These findings suggest that while mesolimbic dopamine projection regions show greater sensitivity to the magnitude of future rewards, lateral cortical regions show greater (negative) sensitivity to the delay of future rewards, potentially reconciling different neural accounts of temporal discounting.
View details for DOI 10.1016/j.neuroimage.2008.11.004
View details for Web of Science ID 000263862900017
View details for PubMedID 19071223
Saving for the future self: Neural measures of future self-continuity predict temporal discounting
SOCIAL COGNITIVE AND AFFECTIVE NEUROSCIENCE
2009; 4 (1): 85-92
Despite increases in the human life span, people have not increased their rate of saving. In a phenomenon known as 'temporal discounting', people value immediate gains over future gains. According to a future self-continuity hypothesis, individuals perceive and treat the future self differently from the present self, and so might fail to save for their future. Neuroimaging offers a novel means of testing this hypothesis, since previous research indicates that self- vs other-judgments elicit activation in the rostral anterior cingulate (rACC). Using event-related functional magnetic resonance imaging, we predicted and found not only individual differences in rACC activation while rating the current vs future self, but also that individual differences in current vs future self activation predicted temporal discounting assessed behaviorally a week after scanning. In addition to supporting the future self-continuity hypothesis, these findings hold implications for significant financial decisions, such as choosing whether to save for the future or spend in the present.
View details for DOI 10.1093/scan/nsn042
View details for Web of Science ID 000264398000009
View details for PubMedID 19047075
Anticipatory affect: neural correlates and consequences for choice
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES
2008; 363 (1511): 3771-3786
'Anticipatory affect' refers to emotional states that people experience while anticipating significant outcomes. Historically, technical limitations have made it difficult to determine whether anticipatory affect influences subsequent choice. Recent advances in the spatio-temporal resolution of functional magnetic resonance imaging, however, now allow researchers to visualize changes in neural activity seconds before choice occurs. We review evidence that activation in specific brain circuits changes during anticipation of monetary incentives, that this activation correlates with affective experience and that activity in these circuits may influence subsequent choice. Specifically, an activation likelihood estimate meta-analysis of cued response studies indicates that nucleus accumbens (NAcc) activation increases during gain anticipation relative to loss anticipation, while anterior insula activation increases during both loss and gain anticipation. Additionally, anticipatory NAcc activation correlates with self-reported positive arousal, whereas anterior insula activation correlates with both self-reported negative and positive arousal. Finally, NAcc activation precedes the purchase of desirable products and choice of high-risk gambles, whereas anterior insula activation precedes the rejection of overpriced products and choice of low-risk gambles. Together, these findings support a neurally plausible framework for understanding how anticipatory affect can influence choice.
View details for DOI 10.1098/rstb.2008.0155
View details for Web of Science ID 000260864600002
View details for PubMedID 18829428
Interpretable Classifiers for fMRI Improve Prediction of Purchases
IEEE TRANSACTIONS ON NEURAL SYSTEMS AND REHABILITATION ENGINEERING
2008; 16 (6): 539-548
Despite growing interest in applying machine learning to neuroimaging analyses, few studies have gone beyond classifying sensory input to directly predicting behavioral output. With spatial resolution on the order of millimeters and temporal resolution on the order of seconds, functional magnetic resonance imaging (fMRI) is a promising technology for such applications. However, fMRI data's low signal-to-noise ratio, high dimensionality, and extensive spatiotemporal correlations present formidable analytic challenges. Here, we apply different machine-learning algorithms to previously acquired data to examine the ability of fMRI activation in three regions-the nucleus accumbens (NAcc), medial prefrontal cortex (MPFC), and insula-to predict purchasing. Our goal was to improve spatiotemporal interpretability as well as classification accuracy. To this end, sparse penalized discriminant analysis (SPDA) enabled automatic selection of correlated variables, yielding interpretable models that generalized well to new data. Relative to logistic regression, linear discriminant analysis, and linear support vector machines, SPDA not only increased interpretability but also improved classification accuracy. SPDA promises to allow more precise inferences about when specific brain regions contribute to purchasing decisions. More broadly, this approach provides a general framework for using neuroimaging data to build interpretable models, including those that predict choice.
View details for DOI 10.1109/TNSRE.2008.926701
View details for Web of Science ID 000262557000004
View details for PubMedID 19144586
Incentive-elicited striatal activation in adolescent children of alcoholics
2008; 103 (8): 1308-1319
Deficient recruitment of motivational circuitry by non-drug rewards has been postulated as a pre-morbid risk factor for substance dependence (SD). We tested whether parental alcoholism, which confers risk of SD, is correlated with altered recruitment of ventral striatum (VS) by non-drug rewards in adolescence.During functional magnetic resonance imaging, adolescent children of alcoholics (COA; age 12-16 years) with no psychiatric disorders (including substance abuse) and similarly aged children with no risk factors responded to targets to win or avoid losing $0, $0.20, $1, $5 or a variable amount (ranging from $0.20 to $5).In general, brain activation by either reward anticipation or outcome notification did not differ between COA and age/gender-matched controls. Cue-elicited reward anticipation activated portions of VS in both COA and controls. In nucleus accumbens (NAcc), signal change increased with anticipated reward magnitude (with intermediate recruitment by variable incentives) but not with loss magnitudes. Reward deliveries activated the NAcc and mesofrontal cortex in both COA and controls. Losses activated anterior insula bilaterally in both groups, with more extensive right anterior insula activation by losses in controls. NAcc signal change during anticipation of maximum rewards (relative to non-reward) correlated positively with both Brief Sensation-Seeking Scale scores and with self-reported excitement in response to maximum reward cues (relative to cues for non-reward).Among adolescents with no psychiatric disorders, incentive-elicited VS activation may relate more to individual differences in sensation-seeking personality than to presence of parental alcoholism alone. Future research could focus on adolescents with behavior disorders or additional risk factors.
View details for DOI 10.1111/j.1360-0443.2008.02250.x
View details for Web of Science ID 000257692800010
View details for PubMedID 18851716
Neural antecedents of the endowment effect
2008; 58 (5): 814-822
The "endowment effect" refers to the tendency to place greater value on items that one owns-an anomaly that violates the reference-independence assumption of rational choice theories. We investigated neural antecedents of the endowment effect in an event-related functional magnetic resonance imaging (fMRI) study. During scanning, 24 subjects considered six products paired with 18 different prices under buying, choosing, or selling conditions. Subjects showed greater nucleus accumbens (NAcc) activation for preferred products across buy and sell conditions combined, but greater mesial prefrontal cortex (MPFC) activation in response to low prices when buying versus selling. During selling, right insular activation for preferred products predicted individual differences in susceptibility to the endowment effect. These findings are consistent with a reference-dependent account in which ownership increases value by enhancing the salience of the possible loss of preferred products.
View details for DOI 10.1016/j.neuron.2008.05.018
View details for Web of Science ID 000256870800017
View details for PubMedID 18549791
Affect dynamics, affective forecasting, and aging
2008; 8 (3): 318-330
Affective forecasting, experienced affect, and recalled affect were compared in younger and older adults during a task in which participants worked to win and avoid losing small monetary sums. Dynamic changes in affect were measured along valence and arousal dimensions, with probes during both anticipatory and consummatory task phases. Older and younger adults displayed distinct patterns of affect dynamics. Younger adults reported increased negative arousal during loss anticipation and positive arousal during gain anticipation. In contrast, older adults reported increased positive arousal during gain anticipation but showed no increase in negative arousal on trials involving loss anticipation. Additionally, younger adults reported large increases in valence after avoiding an anticipated loss, but older adults did not. Younger, but not older, adults exhibited forecasting errors on the arousal dimension, underestimating increases in arousal during anticipation of gains and losses and overestimating increases in arousal in response to gain outcomes. Overall, the findings are consistent with a growing literature suggesting that older people experience less negative emotion than their younger counterparts and further suggest that they may better predict dynamic changes in affect.
View details for DOI 10.1037/1528-35184.108.40.2068
View details for Web of Science ID 000256512900002
View details for PubMedID 18540748
Individual differences in insular sensitivity during loss anticipation predict avoidance learning
2008; 19 (4): 320-323
The anterior insula has been implicated in both the experience and the anticipation of negative outcomes. Although individual differences in insular sensitivity have been associated with self-report measures of chronic anxiety, previous research has not examined whether individual differences in insular sensitivity predict learning to avoid aversive stimuli. In the present study, insular sensitivity was assessed as participants anticipated monetary losses while undergoing functional magnetic resonance imaging. We found that insular responsiveness to anticipated losses predicted participants' ability to learn to avoid losses (but not to approach gains) in a behavioral test several months later. These findings suggest that in addition to correlating with self-reported anxiety, heightened insular sensitivity may promote learning to avoid loss.
View details for Web of Science ID 000254792000003
View details for PubMedID 18399882
Neural responses to monetary incentives in major depression
2008; 63 (7): 686-692
Reduced responsiveness to positive incentives is a central feature of Major Depressive Disorder (MDD). In the present study, we compared neural correlates of monetary incentive processing in unmedicated depressed participants and never-depressed control subjects.Fourteen currently depressed and 12 never-depressed participants underwent functional magnetic resonance imaging while participating in a monetary incentive delay task. During the task, participants were cued to anticipate and respond to a rapidly presented target to gain or avoid losing varying amounts of money.Depressed and never-depressed participants did not differ in nucleus accumbens (NAcc) activation or in affective or behavioral responses during gain anticipation. Depressed participants did, however, exhibit increasing anterior cingulate activation during anticipation of increasing gains, whereas never-depressed participants showed increasing anterior cingulate activation during anticipation of increasing loss. Depressed participants also showed reduced discrimination of gain versus nongain outcomes.The present findings indicate that although unmedicated depressed individuals have the capacity to experience positive arousal and recruit NAcc activation during gain anticipation, they also exhibit increased anterior cingulate cortex activation, suggestive of increased conflict during anticipation of gains, in addition to showing reduced discrimination of gain versus nongain outcomes.
View details for DOI 10.1016/j.biopsych.2007.07.023
View details for Web of Science ID 000254107100008
View details for PubMedID 17916330
Nucleus accumbens activation mediates the influence of reward cues on financial risk taking
2008; 19 (5): 509-513
In functional magnetic resonance imaging research, nucleus accumbens (NAcc) activation spontaneously increases before financial risk taking. As anticipation of diverse rewards can increase NAcc activation, even incidental reward cues may influence financial risk taking. Using event-related functional magnetic resonance imaging, we predicted and found that anticipation of viewing rewarding stimuli (erotic pictures for 15 heterosexual men) increased financial risk taking, and that this effect was partially mediated by increases in NAcc activation. These results are consistent with the notion that incidental reward cues influence financial risk taking by altering anticipatory affect, and so identify a neuropsychological mechanism that may underlie effective emotional appeals in financial, marketing, and political domains.
View details for Web of Science ID 000254372100001
View details for PubMedID 18388729
Valence and salience contribute to nucleus accumbens activation
2008; 39 (1): 538-547
Different accounts of nucleus accumbens (NAcc) function have emphasized its role in representing either valence or salience during incentive anticipation. In an event-related FMRI experiment, we independently manipulated valence and salience by cuing participants to anticipate certain and uncertain monetary gains and losses. NAcc activation correlated with both valence and salience. On trials with certain outcomes, NAcc activation increased for anticipated gains and decreased for anticipated losses. On trials with uncertain outcomes, NAcc activation increased for both anticipated gains and losses but did not differ between them. These findings suggest that NAcc activation separately represents both valence and salience, consistent with its hypothesized role in appetitive motivation.
View details for DOI 10.1016/j.neuroimage.2007.08.009
View details for Web of Science ID 000251406000048
View details for PubMedID 17904386
Neural antecedents of financial decisions
JOURNAL OF NEUROSCIENCE
2007; 27 (31): 8174-8177
To explain investing decisions, financial theorists invoke two opposing metrics: expected reward and risk. Recent advances in the spatial and temporal resolution of brain imaging techniques enable investigators to visualize changes in neural activation before financial decisions. Research using these methods indicates that although the ventral striatum plays a role in representation of expected reward, the insula may play a more prominent role in the representation of expected risk. Accumulating evidence also suggests that antecedent neural activation in these regions can be used to predict upcoming financial decisions. These findings have implications for predicting choices and for building a physiologically constrained theory of decision-making.
View details for DOI 10.1523/JNEUROSCI.1564-07.2007
View details for Web of Science ID 000248502200006
View details for PubMedID 17670962
Anticipation of monetary gain but not loss in healthy older adults
2007; 10 (6): 787-791
Although global declines in structure have been documented in the aging human brain, little is known about the functional integrity of the striatum and prefrontal cortex in older adults during incentive processing. We used event-related functional magnetic resonance imaging to determine whether younger and older adults differed in both self-reported and neural responsiveness to anticipated monetary gains and losses. The present study provides evidence for intact striatal and insular activation during gain anticipation with age, but shows a relative reduction in activation during loss anticipation. These findings suggest that there is an asymmetry in the processing of gains and losses in older adults that may have implications for decision-making.
View details for DOI 10.1038/nn1894
View details for Web of Science ID 000246799800022
View details for PubMedID 17468751
- Affective influence on judgments and decisions: Moving towards core mechanisms REVIEW OF GENERAL PSYCHOLOGY 2007; 11 (2): 179-192
Linking nucleus accumbens dopamine and blood oxygenation
2007; 191 (3): 813-822
Animal research suggests that anticipation of reward can elicit dopamine release in the nucleus accumbens (NAcc). Human functional magnetic resonance imaging (FMRI) research further suggests that reward anticipation can increase local blood oxygen level dependent (BOLD) signal in the NAcc. However, the physiological relationship between dopamine release and BOLD signal increases in the NAcc has not yet been established.This review considers pharmacological MRI (phMRI) evidence for a directional relationship between NAcc dopamine release and BOLD signal, as well as implications for human psychopathological symptoms.Accumulating phMRI evidence supports a simple model in which NAcc dopamine release activates postsynaptic D1 receptors, which changes postsynaptic membrane potential, eventually increasing local BOLD signal. This continuing influence can change on a second-to-second basis.Dopamine release in the NAcc appears to increase local BOLD signal via agonism of postsynaptic D1 receptors. Such a physiological mechanism implies that FMRI may be used to track symptoms related to NAcc dopaminergic dysregulation in psychiatric disorders including schizophrenia and attention deficit/hyperactivity disorder.
View details for DOI 10.1007/s00213-006-0686-7
View details for Web of Science ID 000244691500032
View details for PubMedID 17279377
Neural predictors of purchases
2007; 53 (1): 147-156
Microeconomic theory maintains that purchases are driven by a combination of consumer preference and price. Using event-related fMRI, we investigated how people weigh these factors to make purchasing decisions. Consistent with neuroimaging evidence suggesting that distinct circuits anticipate gain and loss, product preference activated the nucleus accumbens (NAcc), while excessive prices activated the insula and deactivated the mesial prefrontal cortex (MPFC) prior to the purchase decision. Activity from each of these regions independently predicted immediately subsequent purchases above and beyond self-report variables. These findings suggest that activation of distinct neural circuits related to anticipatory affect precedes and supports consumers' purchasing decisions.
View details for DOI 10.1016/j.neuron.2006.11.010
View details for Web of Science ID 000245126500015
View details for PubMedID 17196537
Splitting the difference - How does the brain code reward episodes?
REWARD AND DECISION MAKING IN CORTICOBASAL GANGLIA NETWORKS
2007; 1104: 54-69
Animal research and human brain imaging findings suggest that reward processing involves distinct anticipation and outcome phases. Error terms in popular models of reward learning (such as the temporal difference [TD] model) do not distinguish between the updating of expectations in response to reward cues and outcomes. Thus, correlating a single error term with neural activation assumes recruitment of similar neural substrates at each update. Here, we split the error term to separately model reward prediction and prediction errors, and compare the fit of single versus split error terms to functional magnetic resonance imaging (FMRI) data acquired during a monetary incentive delay task. We speculate and find that while the nucleus accumbens computes gain prediction in response to cues, the mesial prefrontal cortex (MPFC) computes gain prediction errors in response to outcomes. In addition to offering a more comprehensive and anatomically situated view of reward processing, split error terms generate novel predictions about psychiatric symptoms and lesion-induced deficits.
View details for DOI 10.1196/annals.1390.020
View details for Web of Science ID 000248194800005
View details for PubMedID 17416922
The lure of the unknown
2006; 51 (3): 280-282
Using event-related fMRI, Bunzeck and Düzel show that midbrain regions putatively housing dopamine cell bodies activate more for novel pictures than for negative pictures, pictures requiring a motor response, or repeated pictures. These findings indicate that midbrain regions preferentially respond to novelty and suggest that novelty can serve as its own reward.
View details for DOI 10.1016/j.neuron.2006.07.017
View details for Web of Science ID 000239908800003
View details for PubMedID 16880122
Cultural variation in affect valuation
JOURNAL OF PERSONALITY AND SOCIAL PSYCHOLOGY
2006; 90 (2): 288-307
The authors propose that how people want to feel ("ideal affect") differs from how they actually feel ("actual affect") and that cultural factors influence ideal more than actual affect. In 2 studies, controlling for actual affect, the authors found that European American (EA) and Asian American (AA) individuals value high-arousal positive affect (e.g., excitement) more than do Hong Kong Chinese (CH). On the other hand, CH and AA individuals value low-arousal positive affect (e.g., calm) more than do EA individuals. For all groups, the discrepancy between ideal and actual affect correlates with depression. These findings illustrate the distinctiveness of ideal and actual affect, show that culture influences ideal affect more than actual affect, and indicate that both play a role in mental health.
View details for DOI 10.1037/0022-35220.127.116.118
View details for Web of Science ID 000236445600007
View details for PubMedID 16536652
The neural basis of financial risk taking
2005; 47 (5): 763-770
Investors systematically deviate from rationality when making financial decisions, yet the mechanisms responsible for these deviations have not been identified. Using event-related fMRI, we examined whether anticipatory neural activity would predict optimal and suboptimal choices in a financial decision-making task. We characterized two types of deviations from the optimal investment strategy of a rational risk-neutral agent as risk-seeking mistakes and risk-aversion mistakes. Nucleus accumbens activation preceded risky choices as well as risk-seeking mistakes, while anterior insula activation preceded riskless choices as well as risk-aversion mistakes. These findings suggest that distinct neural circuits linked to anticipatory affect promote different types of financial choices and indicate that excessive activation of these circuits may lead to investing mistakes. Thus, consideration of anticipatory neural mechanisms may add predictive power to the rational actor model of economic decision making.
View details for DOI 10.1016/j.neuron.2005.08.008
View details for Web of Science ID 000231782700016
View details for PubMedID 16129404
Functional magnetic resonance imaging of reward prediction
CURRENT OPINION IN NEUROLOGY
2005; 18 (4): 411-417
Technical and conceptual advances in functional magnetic resonance imaging now allow visualization of real-time changes in oxygenation of deep subcortical regions, leading to rapid advances in scientific characterization of the neural substrates that underlie reward prediction in humans.Neuroimaging research over the past year has focused on determining the necessary neural substrates for reward prediction.While the orbitofrontal cortex has long been implicated in modality-specific reward representation, the ventral striatum (particularly the nucleus accumbens) may play a role in modality-independent representations of predicted reward. On the other hand, the mesial prefrontal cortex appears to play a role in representing reward prediction error and the dorsal caudate in linking reward to behavior. Theoretically, future studies will need to establish the specificity of these responses to reward versus punishment and anticipation versus outcome. Clinically, current findings suggest that patients can predict reward without a prefrontal cortex, but should experience difficulty correcting their behavior when reward predictions are violated.
View details for Web of Science ID 000231075100009
View details for PubMedID 16003117
Distributed neural representation of expected value
JOURNAL OF NEUROSCIENCE
2005; 25 (19): 4806-4812
Anticipated reward magnitude and probability comprise dual components of expected value (EV), a cornerstone of economic and psychological theory. However, the neural mechanisms that compute EV have not been characterized. Using event-related functional magnetic resonance imaging, we examined neural activation as subjects anticipated monetary gains and losses that varied in magnitude and probability. Group analyses indicated that, although the subcortical nucleus accumbens (NAcc) activated proportional to anticipated gain magnitude, the cortical mesial prefrontal cortex (MPFC) additionally activated according to anticipated gain probability. Individual difference analyses indicated that, although NAcc activation correlated with self-reported positive arousal, MPFC activation correlated with probability estimates. These findings suggest that mesolimbic brain regions support the computation of EV in an ascending and distributed manner: whereas subcortical regions represent an affective component, cortical regions also represent a probabilistic component, and, furthermore, may integrate the two.
View details for DOI 10.1523/JNEUROSCI.0642-05.2005
View details for Web of Science ID 000229038300014
View details for PubMedID 15888656
Remembrance of rewards past
2005; 45 (3): 331-332
Using event-related fMRI, Wittmann and colleagues report in this issue of Neuron that reward value enhances cue memory and that this process is associated with midbrain modulation of hippocampal consolidation. We propose that their findings introduce a novel mechanism by which positive arousal induced by reward anticipation may promote memory.
View details for DOI 10.1016/j.neuron.2005.01.020
View details for Web of Science ID 000226787700004
View details for PubMedID 15694318
- Sweet revenge? SCIENCE 2004; 305 (5688): 1246-1247
Amphetamine modulates human incentive processing
2004; 43 (2): 261-269
Research suggests that psychostimulants can physiologically alter dopamine kinetics in the ventral striatum (VS) and psychologically enhance mood and attention. Using event-related functional magnetic resonance imaging (fMRI), we conducted a within-subject, double-blind, placebo (PLAC)-controlled study of the effects of oral dextroamphetamine (AMPH, 0.25 mg/kg) treatment on brain activity and affect during incentive processing. In two counterbalanced scanning sessions 60-180 min after ingesting AMPH or PLAC, 8 healthy volunteers played a game involving anticipation and receipt of monetary gains and losses. Group and volume of interest analyses suggested that by enhancing tonic over phasic activation, AMPH treatment "equalized" levels of VS activity and positive arousal during anticipation of both gain and loss. These findings suggest that therapeutic effects of amphetamine on incentive processing may involve reducing the difference between anticipation of gains and losses.
View details for Web of Science ID 000222905400014
View details for PubMedID 15260961
Voxel-based homogeneity probability maps of grapy matter in groups: assessing the reliability of functional effects
2004; 21 (3): 965-972
A subject of increasing importance in magnetic resonance imaging (MRI) is the analysis of intersubject structural differences, particularly when comparing groups of subjects with different conditions or diagnoses. On the other hand, determining structural homogeneity across subjects using voxel-based morphological (VBM) methods has become even more important to investigators who test for group brain activation using functional magnetic resonance images (fMRI) or positron emission tomography (PET). In the absence of methods that evaluate structural differences, one does not know how much reliability to assign to the functional differences. Here, we describe a voxel-based method for quantitatively assessing the homogeneity of tissues from structural magnetic resonance images of groups. Specifically, this method determines the homogeneity of gray matter for a group of subjects. Homogeneity probability maps (HPMs) of a given tissue type (e.g., gray matter) are generated by using a confidence interval based on binomial distribution. These maps indicate for each voxel the probability that the tissue type is gray for the population being studied. Therefore, HPMs can accompany functional analyses to indicate the confidence one can assign to functional difference at any given voxel. In this paper, examples of HPMs generated for a group of control subjects are shown and discussed. The application of this method to functional analysis is demonstrated.
View details for DOI 10.1016/j.neuroimage.2003.10.038
View details for Web of Science ID 000220148900017
View details for PubMedID 15006663
Incentive-elicited brain activation in adolescents: Similarities and differences from young adults
JOURNAL OF NEUROSCIENCE
2004; 24 (8): 1793-1802
Brain motivational circuitry in human adolescence is poorly characterized. One theory holds that risky behavior in adolescence results in part from a relatively overactive ventral striatal (VS) motivational circuit that readily energizes approach toward salient appetitive cues. However, other evidence fosters a theory that this circuit is developmentally underactive, in which adolescents approach more robust incentives (such as risk taking or drug experimentation) to recruit this circuitry. To help resolve this, we compared brain activation in 12 adolescents (12-17 years of age) and 12 young adults (22-28 years of age) while they anticipated the opportunity to respond to obtain monetary gains as well as to avoid monetary losses. In both age groups, anticipation of potential gain activated portions of the VS, right insula, dorsal thalamus, and dorsal midbrain, where the magnitude of VS activation was sensitive to gain amount. Notification of gain outcomes (in contrast with missed gains) activated the mesial frontal cortex (mFC). Across all subjects, signal increase in the right nucleus accumbens during anticipation of responding for large gains independently correlated with both age and self-rated excitement about the high gain cue. In direct comparison, adolescents evidenced less recruitment of the right VS and right-extended amygdala while anticipating responding for gains (in contrast with anticipation of nongains) compared with young adults. However, brain activation after gain outcomes did not appreciably differ between age groups. These results suggest that adolescents selectively show reduced recruitment of motivational but not consummatory components of reward-directed behavior.
View details for DOI 10.1523/JNEUROSCI.4862-03.2004
View details for Web of Science ID 000189210300001
View details for PubMedID 14985419
A region of mesial prefrontal cortex tracks monetarily rewarding outcomes: characterization with rapid event-related fMRI
2003; 18 (2): 263-272
The function of the mesial prefrontal cortex (MPFC: including Brodman areas 10/12/32) remains an enigma. Current theories suggest a role in representing internal information, including emotional introspection, autonomic control, and a "default state" of semantic processing. Recent evidence also suggests that parts of this region may also play a role in processing reward outcomes. In this study, we investigated the possibility that a region of the MPFC would be preferentially recruited by monetary reward outcomes using a parametric monetary incentive delay (MID) task. Twelve healthy volunteers participated in functional magnetic resonance scans while playing the MID task. Group analyses indicated that while the ventral striatum was recruited by anticipation of monetary reward, a region of the MPFC instead responded to rewarding monetary outcomes. Specifically, volume-of-interest analyses indicated that when volunteers received $5.00 after anticipating a $5.00 win, MPFC activity increased, whereas when volunteers did not receive $5.00 after anticipating a $5.00 win, MPFC activity decreased, relative to outcomes with no incentive value. These findings suggest that in the context of processing monetary rewards, a region of the MPFC preferentially tracks rewarding outcomes.
View details for DOI 10.1016/S1053-8119(02)00057-5
View details for Web of Science ID 000181182500007
View details for PubMedID 12595181
- Amygdalar recruitment during anticipation of monetary rewards - An event-related fMRI study AMYGDALA IN BRAIN FUNCTION: BASIC AND CLINICAL APPROACHES 2003; 985: 476-478
Ultrasonic Vocalizations as indices of affective states in rats
2002; 128 (6): 961-977
Adult rats spontaneously vocalize in ultrasonic frequencies. Although these ultrasonic vocalizations (USVs) have been described as by-products of locomotor activity or social signals, accumulating evidence suggests that they may also index anticipatory affective states. Converging ethological, pharmacological, and brain stimulation research indicates that whereas long low-frequency (> 0.3-s, approximately 22-kHz) USVs occur during anticipation of punishment or avoidance behavior, short, high-frequency (< 0.3-s, approximately 50-kHz) USVs typically occur during anticipation of reward or approach behavior. Thus, long 22-kHz USVs may index a state of negative activation, whereas short, 50-kHz USVs may instead index a state of positive activation. This hypothesis has theoretical implications for understanding the brain circuitry underlying mammalian affective states and clinical applicability for modeling hedonic properties of different psychotropic compounds.
View details for DOI 10.1037//0033-2909.128.6.961
View details for Web of Science ID 000178726100005
View details for PubMedID 12405139
The role of brain emotional systems in addictions: a neuro-evolutionary perspective and new 'self-report' animal model
2002; 97 (4): 459-469
The evolutionary significance of neurochemical events in the brain has received minimal attention in the field of addiction research. Likewise, the general failure of neuroscientists to postulate how basic brain circuits might mediate emotional urges has retarded the development of scientific perspectives that could inform new inquiries into the underlying dynamics and treatment of addictions. In this paper, we revisit the argument that prototypically abused substances activate or alter specific emotional brain systems that were evolutionarily designed to signal potential increments or decrements in fitness. We then discuss two distinct emotional systems (reward seeking and separation distress) which may track different types of potential changes in fitness. Based on this evolutionarily inspired approach, we illustrate how a mammalian model of emotion (i.e. rodent ultrasonic vocalizations) may enable scientists to predict drug-related phenomena such as abuse potential, anatomical location of mediating neural substrates, and the psychological impact of withdrawal. We conclude by discussing some therapeutic and social implications of examining drug addiction processes with multiple emotional brain systems in mind.
View details for Web of Science ID 000174850900009
View details for PubMedID 11964061
Dissociation of reward anticipation and outcome with event-related fMRI
2001; 12 (17): 3683-3687
Reward processing involves both appetitive and consummatory phases. We sought to examine whether reward anticipation vs outcomes would recruit different regions of ventral forebrain circuitry using event-related fMRI. Nine healthy volunteers participated in a monetary incentive delays task in which they either responded to a cued target for monetary reward, responded to a cued target for no reward, or did not respond to a cued target during scanning. Multiple regression analyses indicated that while anticipation of reward vs non-reward activated foci in the ventral striatum, reward vs non-reward outcomes activated foci in the ventromedial frontal cortex. These findings suggest that reward anticipation and outcomes may differentially recruit distinct regions that lie along the trajectory of ascending dopamine projections.
View details for Web of Science ID 000172397000012
View details for PubMedID 11726774
Negative association of neuroticism with brain volume ratio in healthy humans
2001; 50 (9): 685-690
Brain volume decreases with normal aging. We sought to determine whether, in addition to age, individual differences in stress reactivity (i.e., neuroticism) would also predict reductions in brain volume.Brain volume ratios were calculated for a sample of 86 healthy volunteers, based on segmented brain volumes taken from T(1)-weighted magnetic resonance imaging and corrected for intracranial volume. Standardized self-reported measures of dispositional neuroticism were concurrently obtained by administering the Revised NEO Personality Inventory.After statistically controlling for age and sex, neuroticism showed a significant negative association with the ratio of brain to the remainder of the intracranial volume, but was not related to intracranial volume itself. In particular, subfactors of neuroticism related to the chronic experience of arousing negative emotions were associated with reduced brain ratio.These results suggest that individual differences in stress reactivity contribute to reductions in brain volume observed during adulthood.
View details for Web of Science ID 000172035100005
View details for PubMedID 11704075
Anticipation of increasing monetary reward selectively recruits nucleus accumbens
JOURNAL OF NEUROSCIENCE
2001; 21 (16)
Comparative studies have implicated the nucleus accumbens (NAcc) in the anticipation of incentives, but the relative responsiveness of this neural substrate during anticipation of rewards versus punishments remains unclear. Using event-related functional magnetic resonance imaging, we investigated whether the anticipation of increasing monetary rewards and punishments would increase NAcc blood oxygen level-dependent contrast (hereafter, "activation") in eight healthy volunteers. Whereas anticipation of increasing rewards elicited both increasing self-reported happiness and NAcc activation, anticipation of increasing punishment elicited neither. However, anticipation of both rewards and punishments activated a different striatal region (the medial caudate). At the highest reward level ($5.00), NAcc activation was correlated with individual differences in self-reported happiness elicited by the reward cues. These findings suggest that whereas other striatal areas may code for expected incentive magnitude, a region in the NAcc codes for expected positive incentive value.
View details for Web of Science ID 000170318200001
View details for PubMedID 11459880
Nucleus accumbens amphetamine microinjections unconditionally elicit 50-kHz ultrasonic vocalizations in rats
2001; 115 (4): 940-944
The authors have hypothesized that, in adult rats, 50-kHz ultrasonic vocalizations (USVs) index a state characterized by high arousal and expectations of reward. This study was conducted to investigate whether dopamine agonism of the nucleus accumbens (NAcc) could evoke such an appetitive state, by examining the effects of NAcc amphetamine (AMPH) microinjections on USVs. Intra-NAcc AMPH injections (0.3, 1.0, 3.0, 10.0 microg unilaterally) produced robust, dose-dependent increases in 50-kHz USVs, which could not be accounted for by concomitant increases in locomotor activity (LA). However, AMPH injections into dorsal control caudate putamen sites produced a modest, dose-dependent increase in LA without significant increases in 50-kHz USVs. These findings indicate that NAcc AMPH microinjections selectively evoke 50-kHz USVs in rats, supporting the notion that dopamine elevations in the NAcc may unconditionally elicit a state of reward anticipation.
View details for Web of Science ID 000170911600020
View details for PubMedID 11508733
Evaluation of rat ultrasonic vocalizations as predictors of the conditioned aversive effects of drugs
2001; 155 (1): 35-42
Since cues that predict aversive outcomes can elicit both avoidance and 20 kHz ultrasonic vocalizations (USVs) in adult rats, 20 kHz USVs may also index the conditioned aversive effects of drugs.We evaluated whether exposure to compartments associated with drugs with aversive effects would selectively increase 20 but not 50 kHz USVs in rats.Rats were injected with naloxone (NAL) or lithium chloride (LiCl) and placed in one compartment or with saline (VEH) and placed in another compartment for three 50-min conditioning sessions. 20 kHz USVs, 50 kHz USVs, and time spent in each chamber were recorded during subsequent 15-min testing sessions during which rats had access to both compartments (expt 1) or were confined to the drug- or VEH-paired compartment (expt 2).In expt 1, animals conditioned either with NAL (0.3 and 3.0 mg/kg) or LiCl (10 and 30 mg/kg) emitted increased 20 kHz USVs in the drug-paired compartment, relative to VEH-conditioned controls. Conditioning with high doses of both drugs also increased conditioned place aversion and decreased emission of 50 kHz USVs. In expt 2, restriction of animals to the compartment paired with high doses of NAL and LiCl also increased emission of 20 kHz USVs and decreased 50 kHz USVs, relative to VEH-conditioned controls.In rats, cues associated with drugs with aversive effects increase 20 kHz USVs and decrease 50 kHz USVs, suggesting that USVs may provide a useful model for predicting the conditioned aversive effects of drugs.
View details for Web of Science ID 000168522200005
View details for PubMedID 11374334
FMRI visualization of brain activity during a monetary incentive delay task
2000; 12 (1): 20-27
Comparative studies have implicated striatal and mesial forebrain circuitry in the generation of autonomic, endocrine, and behavioral responses for incentives. Using blood oxygen level-dependent functional magnetic resonance imaging, we sought to visualize functional activation of these regions in 12 normal volunteers as they anticipated and responded for monetary incentives. Both individual and group analyses of time-series data revealed significant activation of striatal and mesial forebrain structures (including insula, caudate, putamen, and mesial prefrontal cortex) during trials involving both monetary rewards and punishments. In addition to these areas, during trials involving punishment, group analysis revealed activation foci in the anterior cingulate and thalamus. These results corroborate comparative studies which implicate striatal and mesial forebrain circuitry in the elaboration of incentive-driven behavior. This report also introduces a new paradigm for probing the functional integrity of this circuitry in humans.
View details for Web of Science ID 000088317700003
View details for PubMedID 10875899
Anticipation of rewarding electrical brain stimulation evokes ultrasonic vocalization in rats
2000; 114 (2): 320-327
Adult rats emit increased rates of 50-kHz ultrasonic vocalizations (USVs) before receiving social and pharmacological rewards. This study sought to determine whether anticipation of rewarding electrical stimulation of the brain (ESB) would also elicit these vocalizations. In Experiments 1 and 2, rats showed increased 50-kHz USVs before receiving experimenter-delivered ventral tegmental area (VTA) and lateral hypothalamic (LH) ESB on a fixed time 20-s schedule. In Experiments 3 and 4, rats increased their rate of 50-kHz USVs in response to cues that predicted the opportunity to self-stimulate the VTA or LH. Interestingly, unexpected termination of either type of ESB evoked 20-kHz, rather than 50-kHz, USVs. In Experiment 5, a cue that predicted daily 1-hr feeding sessions increased 50-kHz USVs, whereas a cue that predicted footshock decreased 50-kHz USVs. These effects could not be explained simply by changes in locomotor activity or general arousal. Together, these findings support the hypothesis that short 50-kHz USVs may selectively index a state of reward anticipation in rats.
View details for DOI 10.1037//0735-7044.114.2.320
View details for Web of Science ID 000087492200010
View details for PubMedID 10832793
High-frequency ultrasonic vocalizations index conditioned pharmacological reward in rats
PHYSIOLOGY & BEHAVIOR
1999; 66 (4): 639-643
We have proposed that short (<0.5 s), high-frequency (approximately 50 kHz) ultrasonic vocalizations ("50-kHz USVs") index a positive affective state in adult rats, because they occur prior to rewarding social interactions (i.e., rough-and-tumble play, sex). To evaluate this hypothesis in the case of nonsocial stimuli, we examined whether rats would make increased 50-kHz USVs in places associated with the administration of rewarding pharmacological compounds [i.e., amphetamine (AMPH) and morphine (MORPH)]. In Experiment 1, rats made a greater percentage of 50-kHz USVs on the AMPH-paired side of a two-compartment chamber than on the vehicle-paired side, even after statistical correction for place preference. In Experiment 2, rats made a higher percentage of 50-kHz USVs on the MORPH-paired side than on the vehicle-paired side, despite nonsignificant place preference. These findings support the hypothesis that 50-kHz USVs mark a positive affective state in rats and introduce a novel and rapid marker of pharmacological reward.
View details for Web of Science ID 000080685000013
View details for PubMedID 10386908
Anticipation of play elicits high-frequency ultrasonic vocalizations in young rats
JOURNAL OF COMPARATIVE PSYCHOLOGY
1998; 112 (1): 65-73
The authors provide initial documentation that juvenile rats emit short, high-frequency ultrasonic vocalizations (high USVs, approximately 55 kHz) during rough-and-tumble play. In an observational study, they further observe that these vocalizations both correlate with and predict appetitive components of the play behavioral repertoire. Additional experiments characterized eliciting conditions for high USVs. Without prior play exposure, rats separated by a screen vocalized less than playing rats, but after only 1 play session, separated rats vocalized more than playing rats. This findings suggested that high USVs were linked to a motivational state rather than specific play behaviors or general activity. Furthermore, individual rats vocalized more in a chamber associated with play than in a habituated control chamber. Finally, congruent and incongruent motivational manipulations modulated vocalization expression. Although play deprivation enhanced high USVs, an arousing but aversive stimulus (bright light) reduced them. Taken together, these findings suggest that high USVs may index an appetitive motivation to play in juvenile rats.
View details for Web of Science ID 000072487600007
View details for PubMedID 9528115
- Effects of serotonin depletion on the play of juvenile rats INTEGRATIVE NEUROBIOLOGY OF AFFILIATION 1997; 807: 475-477
Effects of fluoxetine on play dominance in juvenile rats
1996; 22 (4): 297-307
View details for Web of Science ID A1996UZ97900005
ON THE BRAIN AND PERSONALITY SUBSTRATES OF PSYCHOPATHY
BEHAVIORAL AND BRAIN SCIENCES
1995; 18 (3): 568-570
View details for Web of Science ID A1995TJ30000076
SPATIAL SMOOTHING AND THE FUNCTIONAL LOCALIZATION OF NUCLEUS ACCUMBENS ACTIVITY
MIT PRESS. 2013: 231-232
View details for Web of Science ID 000317030501278
REINFORCEMENT LEARNING AND AGE-RELATED CHANGES IN RELATIVE CODING IN MESOLIMBIC BRAIN REGIONS
OXFORD UNIV PRESS INC. 2010: 10-10
View details for Web of Science ID 000286006701049
Facial EMG discriminates gain and loss anticipation and outcome in a monetary incentive delay task
WILEY-BLACKWELL. 2004: S80-S80
View details for Web of Science ID 000223558200310