A common neurobiology for pain and pleasure

A common neurobiology for pain and pleasure
Siri Leknes and Irene Tracey (2008)


Abstract

Pain and pleasure are powerful motivators of behaviour and have historically been considered opposites. Emerging evidence from the pain and reward research fields points to extensive similarities in the anatomical substrates of painful and pleasant sensations. Recent molecular-imaging and animal studies have demonstrated the important role of the opioid and dopamine systems in modulating both pain and pleasure. Understanding the mutually inhibitory effects that pain and reward processing have on each other, and the neural mechanisms that underpin such modulation, is important for alleviating unnecessary suffering and improving well-being.

A Social Neuroscience Perspective on Adolescent Risk-Taking

A Social Neuroscience Perspective on Adolescent Risk-Taking
Laurence Steinberg; 2008


Abstract

This article proposes a framework for theory and research on risk-taking that is informed by developmental neuroscience. Two fundamental questions motivate this review. First, why does risk-taking increase between childhood and adolescence? Second, why does risk-taking decline between adolescence and adulthood? Risk-taking increases between childhood and adolescence as a result of changes around the time of puberty in the brain’s socio-emotional system leading to increased reward-seeking, especially in the presence of peers, fueled mainly by a dramatic remodeling of the brain’s dopaminergic system. Risk-taking declines between adolescence and adulthood because of changes in the brain’s cognitive control system – changes which improve individuals’ capacity for self-regulation. These changes occur across adolescence and young adulthood and are seen in structural and functional changes within the prefrontal cortex and its connections to other brain regions. The differing timetables of these changes make mid-adolescence a time of heightened vulnerability to risky and reckless behavior.

Social bonds in birds are associated with brain size and contingent on the correlated evolution of life-history and increased parental investment

Social bonds in birds are associated with brain size and contingent on the correlated evolution of life-history and increased parental investment
Susanne Schultz & Robin Dunbar; April 2010
Biological Journal of the Linnean Society


Abstract

In birds, large brains are associated with a series of population-level phenomena, including invasion success, species richness, and resilience to population decline. Thus, they appear to open up adaptive opportunities through flexibility in foraging and anti-predator behaviour. The evolutionary pathway leading to large brain size has received less attention than behavioural and ecological correlates. Using a comparative approach, we show that, independent of previously recognized associations with developmental constraints, relative brain size in birds is strongly related to biparental care, pair-bonding, and stable social relationships. We also demonstrate correlated evolution between large relative brain size and altricial development, and that the evolution of both traits is contingent on biparental care. Thus, biparental care facilitates altricial development, which permits the evolution of large relative brain size. Finally, we show that large relative brain size is associated with pair-bond strength, itself a likely consequence of cooperation and negotiation between partners under high levels of parental investment. These analyses provide an evolutionary model for the evolution of and prevalence of biparental care, altricial development, and pair-bonding in birds.

Efficiency of Functional Brain Networks and Intellectual Performance

Efficiency of Functional Brain Networks and Intellectual Performance
Martijn P van den Heuvel et al.; 2009
http://www.jneurosci.org/content/29/23/7619.full


Abstract

Our brain is a complex network in which information is continuously processed and transported between spatially distributed but functionally linked regions. Recent studies have shown that the functional connections of the brain network are organized in a highly efficient small-world manner, indicating a high level of local neighborhood clustering, together with the existence of more long-distance connections that ensure a high level of global communication efficiency within the overall network. Such an efficient network architecture of our functional brain raises the question of a possible association between how efficiently the regions of our brain are functionally connected and our level of intelligence. Examining the overall organization of the brain network using graph analysis, we show a strong negative association between the normalized characteristic path length λ of the resting-state brain network and intelligence quotient (IQ). This suggests that human intellectual performance is likely to be related to how efficiently our brain integrates information between multiple brain regions. Most pronounced effects between normalized path length and IQ were found in frontal and parietal regions. Our findings indicate a strong positive association between the global efficiency of functional brain networks and intellectual performance.

On the genetic basis of face cognition and its relation to fluid cognitive abilities

On the genetic basis of face cognition and its relation to fluid cognitive abilities
A. Kiy et al.; 2013
Genes, Brain & Behavior


Abstract

The oxytocin and the dopaminergic systems have turned out to be highly relevant for social abilities and cognition. Therefore, we examined the association between two functional gene polymorphisms and face cognition (FC) in a multivariate study (N = 250) by applying structural equation modeling. The catechol-O-methyltransferase (COMT) val158met polymorphism influences the enzyme activity of COMT, which affects the prefrontal dopamine concentration. The rs226849 is a single-nucleotide polymorphism located in the promoter region of the oxytocin receptor (OXTR) gene, modulating the mRNA expression. By modeling a general fluid ability factor (defined by working memory and reasoning) and nested FC factors, we tested genetic contributions to FC, after controlling for variance in FC that was also associated with fluid abilities. In line with several previous studies, we found a significant association between the COMT genotype and fluid abilities (Gf) but not with FC. The association between the oxytocin polymorphism and Gf was opposite in direction for men and women. Women with the C⁺ genotype performed better on Gf tasks than those with the C⁻genotype. Conversely, men with the C⁻ genotype performed better than those with the C⁺ genotype. There was no significant association between OXTR and the nested FC factor. Therefore, the relationship between the oxytocin polymorphism and FC can be fully accounted for by Gf. The sex specificity of this relationship is a novel finding and warrants a mechanistic explanation.

Global Connectivity of Prefrontal Cortex Predicts Cognitive Control and Intelligence

Global Connectivity of Prefrontal Cortex Predicts Cognitive Control and Intelligence
Michael W Cole et al.; 2010
http://www.jneurosci.org/content/32/26/8988.full


Abstract

Control of thought and behavior is fundamental to human intelligence. Evidence suggests a frontoparietal brain network implements such cognitive control across diverse contexts. We identify a mechanism—global connectivity—by which components of this network might coordinate control of other networks. A lateral prefrontal cortex (LPFC) region's activity was found to predict performance in a high control demand working memory task and also to exhibit high global connectivity. Critically, global connectivity in this LPFC region, involving connections both within and outside the frontoparietal network, showed a highly selective relationship with individual differences in fluid intelligence. These findings suggest LPFC is a global hub with a brainwide influence that facilitates the ability to implement control processes central to human intelligence.

Bottom-up and top-down emotion generation: implications for emotion regulation

Bottom-up and top-down emotion generation: implications for emotion regulation
Kateri Mc Rae et al., 2012
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3304475/


Abstract

Emotion regulation plays a crucial role in adaptive functioning and mounting evidence suggests that some emotion regulation strategies are often more effective than others. However, little attention has been paid to the different ways emotions can be generated: from the ‘bottom-up’ (in response to inherently emotional perceptual properties of the stimulus) or ‘top-down’ (in response to cognitive evaluations). Based on a process priming principle, we hypothesized that mode of emotion generation would interact with subsequent emotion regulation. Specifically, we predicted that top-down emotions would be more successfully regulated by a top-down regulation strategy than bottom-up emotions. To test this hypothesis, we induced bottom-up and top-down emotions, and asked participants to decrease the negative impact of these emotions using cognitive reappraisal. We observed the predicted interaction between generation and regulation in two measures of emotional responding. As measured by self-reported affect, cognitive reappraisal was more successful on top-down generated emotions than bottom-up generated emotions. Neurally, reappraisal of bottom-up generated emotions resulted in a paradoxical increase of amygdala activity. This interaction between mode of emotion generation and subsequent regulation should be taken into account when comparing of the efficacy of different types of emotion regulation, as well as when reappraisal is used to treat different types of clinical disorders.

Neurobehavioral Evidence for Changes in Dopamine System Activity During Adolescence

Neurobehavioral Evidence for Changes in Dopamine System Activity During Adolescence
Dustin Wahlstrom et al., 2010
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2845533/


Abstract

Human adolescence has been characterized by increases in risk-taking, emotional lability, and deficient patterns of behavioral regulation. These behaviors have often been attributed to changes in brain structure that occur during this developmental period, notably alterations in gray and white matter that impact synaptic architecture in frontal, limbic, and striatal regions. In this review, we provide a rationale for considering that these behaviors may be due to changes in dopamine system activity, particularly overactivity, during adolescence relative to either childhood or adulthood. This rationale relies on animal data due to limitations in assessing neurochemical activity more directly in juveniles. Accordingly, we also present a strategy that incorporates molecular genetic techniques to infer the status of the underlying tone of the dopamine system across developmental groups. Implications for the understanding of adolescent behavioral development are discussed.

Shared brain activity for aesthetic and moral judgments: implications for the Beauty-is-Good stereotype

Shared brain activity for aesthetic and moral judgments: implications for the Beauty-is-Good stereotype
Takashi Tsukiura and Roberta Cabeza; 2010
http://intl-scan.oxfordjournals.org/content/6/1/138.full


Abstract

The Beauty-is-Good stereotype refers to the assumption that attractive people possess sociably desirable personalities and higher moral standards. The existence of this bias suggests that the neural mechanisms for judging facial attractiveness and moral goodness overlap. To investigate this idea, we scanned participants with functional magnetic resonance imaging while they made attractiveness judgments about faces and goodness judgments about hypothetical actions. Activity in the medial orbitofrontal cortex increased as a function of both attractiveness and goodness ratings, whereas activity in the insular cortex decreased with both attractiveness and goodness ratings. Within each of these regions, the activations elicited by attractiveness and goodness judgments were strongly correlated with each other, supporting the idea of similar contributions of each region to both judgments. Moreover, activations in orbitofrontal and insular cortices were negatively correlated with each other, suggesting an opposing relationship between these regions during attractiveness and goodness judgments. These findings have implications for understanding the neural mechanisms of the Beauty-is-Good stereotype.

Social power and approach-related neural activity

Social power and approach-related neural activity
Maarten A S Boksem et al.; 2008


Abstract

It has been argued that power activates a general tendency to approach whereas powerlessness activates a tendency to inhibit. The assumption is that elevated power involves reward-rich environments, freedom and, as a consequence, triggers an approach-related motivational orientation and attention to rewards. In contrast, reduced power is associated with increased threat, punishment and social constraint and thereby activates inhibition-related motivation. Moreover, approach motivation has been found to be associated with increased relative left-sided frontal brain activity, while withdrawal motivation has been associated with increased right sided activations. We measured EEG activity while subjects engaged in a task priming either high or low social power. Results show that high social power is indeed associated with greater left-frontal brain activity compared to low social power, providing the first neural evidence for the theory that high power is associated with approach-related motivation. We propose a framework accounting for differences in both approach motivation and goal-directed behaviour associated with different levels of power.

The neural basis of semantic and episodic forms of self-knowledge: Insights from Functional Neuroimaging

The neural basis of semantic and episodic forms of self-knowledge: Insights from Functional Neuroimaging
Arnaud D'Argembeau and Eric Salmon; 2011
http://www.ncbi.nlm.nih.gov/books/NBK51092/


Abstract

Throughout evolution, hominids have developed greater capacity to think about themselves in abstract and symbolic ways. This process has reached its apex in humans with the construction of a concept of self as a distinct entity with a personal history. This chapter provides a review of recent functional neuroimaging studies that have investigated the neural correlates of such "higher-level" aspects of the human self, focusing in particular on processes that allow individuals to consciously represent and reflect on their own personal attributes (semantic forms of self-knowledge) and experiences (episodic forms of self-knowledge). These studies point to the medial prefrontal cortex (MPFC) as a key neural structure for processing various kinds of self-referential information. We speculate that the MPFC may mediate dynamic processes that appraise and code the self-relatedness or self-relevance of information. This brain region may thus play a key role in creating the mental model of the self that is displayed in our mind at a given moment.

Relating introspective accuracy to individual differences in brain structure

Relating introspective accuracy to individual differences in brain structure
Stephen M Fleming et al., 2011
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3173849/


Abstract

Our ability to introspect about self-performance is core to human subjective experience, but the neuroanatomical basis of this ability is unknown. Such accurate introspection requires discriminating correct from incorrect decisions, a capacity that varies substantially across individuals. We dissociated variation in introspective ability from objective performance in a simple perceptual decision task, allowing us to determine whether this inter-individual variability was associated with a distinct neural substrate. We show that introspective ability is correlated with gray matter volume in anterior prefrontal cortex, a region which shows striking evolutionary development in humans. Moreover, inter-individual variability in introspective ability also correlated with white matter microstructure connected with this area of prefrontal cortex. Our findings point to a focal neuroanatomical substrate for introspective ability, a substrate distinct from that supporting primary perception.

Prefrontal and striatal dopaminergic genes predict individual differences in exploration and exploitation

Prefrontal and striatal dopaminergic genes predict individual differences in exploration and exploitation
Michael J Frank et al., 2009
http://diyhpl.us/~bryan/papers2/neuro/Prefrontal%20and%20striatal%20dopaminergic%20genes%20predict%20individual%20differences%20in%20exploration%20and%20exploitation.pdf


Abstract

The basal ganglia support learning to exploit decisions that have yielded positive outcomes in the past. In contrast, limited evidence implicates the prefrontal cortex in the process of making strategic exploratory decisions when the magnitude of potential outcomes is unknown. Here we examine neurogenetic contributions to individual differences in these distinct aspects of motivated human behavior, using a temporal decision-making task and computational analysis. We show that two genes controlling striatal dopamine function, DARPP-32 (also called PPP1R1B) and DRD2, are associated with exploitative learning to adjust response times incrementally as a function of positive and negative decision outcomes. In contrast, a gene primarily controlling prefrontal dopamine function (COMT) is associated with a particular type of ‘directed exploration’, in which exploratory decisions are made in proportion to Bayesian uncertainty about whether other choices might produce outcomes that are better than the status quo. Quantitative model fits reveal that genetic factors modulate independent parameters of a reinforcement learning system.

Sources of Cognitive Exploration: Genetic Variation in the Prefrontal Dopamine System Predicts Openness/Intellect

Sources of Cognitive Exploration: Genetic Variation in the Prefrontal Dopamine System Predicts Openness/Intellect

Colin G DeYoung et al; 2012

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3143482/


Abstract

The personality trait Openness/Intellect reflects the tendency to be imaginative, curious, perceptive, artistic, and intellectual—all characteristics that involve cognitive exploration. Little is known about the biological basis of Openness/Intellect, but the trait has been linked to cognitive functions of prefrontal cortex, and the neurotransmitter dopamine plays a key role in motivation to explore. The hypothesis that dopamine is involved in Openness/Intellect was supported by examining its association with two genes that are central components of the prefrontal dopaminergic system. In two demographically different samples (children: N = 608; adults: N = 214), variation in the dopamine D4 receptor gene (DRD4) and the catechol-O-methyltransferase gene (COMT) predicted Openness/Intellect, as main effects in the child sample and in interaction in adults.

Dimensionality of brain networks linked to life-long individual differences in self-control

Dimensionality of brain networks linked to life-long individual differences in self-control
Marc G Bermann et al., 2013
http://selfcontrol.psych.lsa.umich.edu/papers/2013_Bermanetal_Nature.pdf

 

Abstract

The ability to delay gratification in childhood has been linked to positive outcomes in adolescence and adulthood. Here we examine a subsample of participants from a seminal longitudinal study of self-control throughout a subject’s life span. Self-control, first studied in children at age 4 years, is now re-examined 40 years later, on a task that required control over the contents of working memory. We examine whether patterns of brain activation on this task can reliably distinguish participants with consistently low and high self-control abilities (low versus high delayers). We find that low delayers recruit significantly higherdimensional neural networks when performing the task compared with high delayers. High delayers are also more homogeneous as a group in their neural patterns compared with low delayers. From these brain patterns, we can predict with 71% accuracy, whether a participant is a high or low delayer. The present results suggest that dimensionality of neural networks is a biological predictor of self-control abilities.

Chronic sugar intake dampens feeding-related activity of neurons synthesizing a satiety mediator, oxytocin

Chronic sugar intake dampens feeding-related activity of neurons synthesizing a satiety mediator, oxytocin
Anaya Mitra et al., 2010
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3175817/


Abstract

Increased tone of orexigens mediating reward occurs upon repeated consumption of sweet foods. Interestingly, some of these reward orexigens, such as opioids, diminish activity of neurons synthesizing oxytocin, a nonapeptide that promotes satiety and feeding termination. It is not known, however, whether consumption-related activity of the central oxytocin system is modified under chronic sugar feeding reward itself. Therefore, we examined how chronic consumption of a rewarding high-sucrose (HS) vs. bland cornstarch (CS) diet affected the activity of oxytocin cells in the hypothalamus at the time of meal termination. Schedule-fed (2 hrs/day) rats received either a HS or CS powdered diet for 20 days. On the 21st day, they were given the same or the opposite diet, and food was removed after the main consummatory activity was completed. Animals were perfused 60 minutes after feeding termination and brains were immunostained for oxytocin and the marker of neuronal activity, c-Fos. The percentage of c-Fos-positive oxytocin cells in the hypothalamic paraventricular nucleus was significantly lower in rats chronically exposed to the HS than to the CS diet, regardless of which diet they received on the final day. A similar pattern was observed in the supraoptic nucleus. We conclude that the chronic rather than acute sucrose intake reduces activity of the anorexigenic oxytocin system. These findings indicate that chronic consumption of sugar blunts activity of pathways that mediate satiety. We speculate that a reduction in central satiety signaling precipitated by regular intake of foods high in sugar may lead to generalized overeating.

Attention-deficit/hyperactivity disorder: is it time to reappraise the role of sugar consumption?

Attention-deficit/hyperactivity disorder: is it time to reappraise the role of sugar consumption?
Johnson R J et al., 2011


Abstract

Attention-deficit/hyperactivity disorder (ADHD) affects nearly 10% of children in the United States, and the prevalence of this disorder has increased steadily over the past decades. The cause of ADHD is unknown, although recent studies suggest that it may be associated with a disruption in dopamine signaling whereby dopamine D2 receptors are reduced in reward-related brain regions. This same pattern of reduced dopamine-mediated signaling is observed in various reward-deficiency syndromes associated with food or drug addiction, as well as in obesity. While genetic mechanisms are likely contributory to cases of ADHD, the marked frequency of the disorder suggests that other factors are involved in the etiology. In this article, we revisit the hypothesis that excessive sugar intake may have an underlying role in ADHD. We review preclinical and clinical data suggesting overlaps among ADHD, sugar and drug addiction, and obesity. Further, we present the hypothesis that the chronic effects of excessive sugar intake may lead to alterations in mesolimbic dopamine signaling, which could contribute to the symptoms associated with ADHD. We recommend further studies to investigate the possible relationship between chronic sugar intake and ADHD.

Individual differences in personality traits reflect structural variance in specific brain regions

Individual differences in personality traits reflect structural variance in specific brain regions
Simona Gardini et al., 2009
https://syllabus.byu.edu/uploads/gkhHMK7hTKYu.pdf


Abstract

 

Personality dimensions such as novelty seeking (NS), harm avoidance (HA), reward dependence (RD) and persistence (PER) are said to be heritable, stable across time and dependent on genetic and neurobiological factors. Recently a better understanding of the relationship between personality traits and brain structures/systems has become possible due to advances in neuroimaging techniques. This Magnetic Resonance Imaging (MRI) study investigated if individual differences in these personality traits reflected structural variance in specific brain regions. A large sample of eighty five young adult participants completed the Three-dimensional Personality Questionnaire (TPQ) and had their brain imaged with MRI. A voxel-based correlation analysis was carried out between individuals’ personality trait scores and grey matter volume values extracted from 3D brain scans. NS correlated positively with grey matter volume in frontal and posterior cingulate regions. HA showed a negative correlation with grey matter volume in orbito-frontal, occipital and parietal structures. RD was negatively correlated with grey matter volume in the caudate nucleus and in the rectal frontal gyrus. PER showed a positive correlation with grey matter volume in the precuneus, paracentral lobule and parahippocampal gyrus. These results indicate that individual differences in the main personality dimensions of NS, HA, RD and PER, may reflect structural variance in specific brain areas.

Food and drug reward: overlapping circuits in human obesity and addiction

Food and drug reward: overlapping circuits in human obesity and addiction
Volkow ND et al., 2012
https://www.bnl.gov/isd/documents/77781.pdf


Abstract

Both drug addiction and obesity can be defined as disorders in which the saliency value of one type of reward (drugs and food, respectively) becomes abnormally enhanced relative to, and at the expense of others. This model is consistent with the fact that both drugs and food have powerful reinforcing effects –partly mediated by dopamine increases in the limbic system- that, under certain circumstances or in vulnerable individuals, could overwhelm the brain’s homeostatic control mechanisms. Such parallels have generated significant interest in understanding the shared vulnerabilities and trajectories between addiction and obesity. Now, brain imaging discoveries have started to uncover common features between these two conditions and to delineate some of the overlapping brain circuits whose dysfunctions may explain stereotypic and related behavioral deficits in human subjects. These results suggest that both obese and drug addicted individuals suffer from impairments in dopaminergic pathways that regulate neuronal systems associated not only with reward sensitivity and incentive motivation, but also with conditioning (memory/learning), impulse control (behavioral inhibition), stress reactivity and interoceptive awareness. Here, we integrate findings predominantly derived from positron emission tomography that investigate the role of dopamine in drug addiction and in obesity and propose an updated working model to help identify treatment strategies that may benefit both of these conditions.

Dysfunction of the prefrontal cortex in addiction

Dysfunction of the prefrontal cortex in addiction: neuroimaging findings and clinical implications
R Z Goldstein & Nora D Volkow, 2011
http://www.nature.com/nrn/journal/v12/n11/full/nrn3119.html


Abstract

 

The loss of control over drug intake that occurs in addiction was initially believed to result from disruption of subcortical reward circuits. However, imaging studies in addictive behaviours have identified a key involvement of the prefrontal cortex (PFC) both through its regulation of limbic reward regions and its involvement in higher-order executive function (for example, self-control, salience attribution and awareness). This Review focuses on functional neuroimaging studies conducted in the past decade that have expanded our understanding of the involvement of the PFC in drug addiction. Disruption of the PFC in addiction underlies not only compulsive drug taking but also accounts for the disadvantageous behaviours that are associated with addiction and the erosion of free will.