Neural basis of utility estimation

Changes in functional connectivity and structural covariance between the fronto-parietal network and medial orbitofrontal cortex are associated with disinhibition in restrained eaters

Disinhibition, characterized by a loss of dietary control, is a significant risk factor for diet failure and the onset of eating disorders in restrained eaters. This study employs resting-state functional connectivity and structural covariance network analyses to explore the neural associations underlying this behavior. By analyzing functional MRI data from 63 female college students, we found that increased disinhibition correlates with enhanced functional connectivity between the medial orbitofrontal cortex and key components of the inhibition system, particularly within the fronto-parietal network. Moreover, we observed a relationship between the structural covariance of the medial orbitofrontal cortex and the inferior parietal lobule and the severity of disinhibition. Importantly, the functional connectivity between the medial orbitofrontal cortex and the inferior parietal lobule predicts the severity of binge eating symptoms in these individuals. These findings indicate that imbalances in the interaction between the brain's reward and inhibition systems can lead to dietary failures and eating disorders, emphasizing the need for targeted interventions.

Parallel processing of value-related information during multi-attribute decisions

When choosing between options with multiple attributes, do we integrate all attributes into a unified measure for comparison, or does the comparison also occur at the level of each attribute, involving parallel processes that can dynamically influence each other? What happens when independent sensory features all carry information about the same decision factor, such as reward value? To investigate these questions, we asked human participants to perform a two-alternative forced choice reaching task in which the reward value of a target was indicated by two visual attributes-its brightness ("bottom-up," BU feature) and its orientation ("top-down," TD feature). If decisions always occur after the integration of both features, there should be no difference in the reaction time (RT) regardless of the attribute combinations that drove the choice. Counter to that prediction, RT distributions depended on the attribute combinations of given targets and the choices made by participants. RTs were shortest when both attributes were congruent or when the choice was based on the bottom-up feature, and longer when the attributes were in conflict (favoring opposite options). In conflict trials, nearly two-thirds of participants made faster decisions when choosing the option favored by the bottom-up feature than when choosing the top-down-favored option. We also observed mid-reach changes-of-mind in a subset of conflict trials, mostly changing from the bottom-up to the top-down-favored target. These data suggest that multi-attribute value-based decisions are better explained by a distributed process including competition among different features than by a competition based on a single, integrated estimate of value.NEW & NOTEWORTHY We show that during value-based decisions, humans do not always use all reward-related information to make their choice, but instead can "jump the gun" using partial information. In particular, when different sources of information were in conflict, early decisions were mostly based on fast bottom-up information, and sometimes followed by corrective changes-of-mind based on slower top-down information. This supports parallel decision processes among different information sources, as opposed to a single integrated "common currency."

The Convergence Model of Brain Reward Circuitry: Implications for Relief of Treatment-Resistant Depression by Deep-Brain Stimulation of the Medial Forebrain Bundle

Deep-brain stimulation of the medial forebrain bundle (MFB) can provide effective, enduring relief of treatment-resistant depression. Panksepp provided an explanatory framework: the MFB constitutes the core of the neural circuitry subserving the anticipation and pursuit of rewards: the “SEEKING” system. On that view, the SEEKING system is hypoactive in depressed individuals; background electrical stimulation of the MFB alleviates symptoms by normalizing activity. Panksepp attributed intracranial self-stimulation to excitation of the SEEKING system in which the ascending projections of midbrain dopamine neurons are an essential component. In parallel with Panksepp’s qualitative work, intracranial self-stimulation has long been studied quantitatively by psychophysical means. That work argues that the predominant directly stimulated substrate for MFB self-stimulation are myelinated, non-dopaminergic fibers, more readily excited by brief electrical current pulses than the thin, unmyelinated axons of the midbrain dopamine neurons. The series-circuit hypothesis reconciles this view with the evidence implicating dopamine in MFB self-stimulation as follows: direct activation of myelinated MFB fibers is rewarding due to their trans-synaptic activation of midbrain dopamine neurons. A recent study in which rats worked for optogenetic stimulation of midbrain dopamine neurons challenges the series-circuit hypothesis and provides a new model of intracranial self-stimulation in which the myelinated non-dopaminergic neurons and the midbrain dopamine projections access the behavioral final common path for reward seeking via separate, converging routes. We explore the potential implications of this convergence model for the interpretation of the antidepressant effect of MFB stimulation. We also discuss the consistent finding that psychomotor stimulants, which boost dopaminergic neurotransmission, fail to provide a monotherapy for depression. We propose that non-dopaminergic MFB components may contribute to the therapeutic effect in parallel to, in synergy with, or even instead of, a dopaminergic component.

Frontal circuit specialisations for decision making

There is widespread consensus that distributed circuits across prefrontal and anterior cingulate cortex (PFC/ACC) are critical for reward-based decision making. The circuit specialisations of these areas in primates were likely shaped by their foraging niche, in which decision making is typically sequential, attention-guided and temporally extended. Here, I argue that in humans and other primates, PFC/ACC circuits are functionally specialised in two ways. First, microcircuits found across PFC/ACC are highly recurrent in nature and have synaptic properties that support persistent activity across temporally extended cognitive tasks. These properties provide the basis of a computational account of time-varying neural activity within PFC/ACC as a decision is being made. Second, the macrocircuit connections (to other brain areas) differ between distinct PFC/ACC cytoarchitectonic subregions. This variation in macrocircuit connections explains why PFC/ACC subregions make unique contributions to reward-based decision tasks and how these contributions are shaped by attention. They predict dissociable neural representations to emerge in orbitofrontal, anterior cingulate and dorsolateral prefrontal cortex during sequential attention-guided choice, as recently confirmed in neurophysiological recordings.

Hof P. Understanding Emotions: Origins and Roles of the Amygdala

Emotions arise from activations of specialized neuronal populations in several parts of the cerebral cortex, notably the anterior cingulate, insula, ventromedial prefrontal, and subcortical structures, such as the amygdala, ventral striatum, putamen, caudate nucleus, and ventral tegmental area. Feelings are conscious, emotional experiences of these activations that contribute to neuronal networks mediating thoughts, language, and behavior, thus enhancing the ability to predict, learn, and reappraise stimuli and situations in the environment based on previous experiences. Contemporary theories of emotion converge around the key role of the amygdala as the central subcortical emotional brain structure that constantly evaluates and integrates a variety of sensory information from the surroundings and assigns them appropriate values of emotional dimensions, such as valence, intensity, and approachability. The amygdala participates in the regulation of autonomic and endocrine functions, decision-making and adaptations of instinctive and motivational behaviors to changes in the environment through implicit associative learning, changes in short- and long-term synaptic plasticity, and activation of the fight-or-flight response via efferent projections from its central nucleus to cortical and subcortical structures.

Partial integration of the components of value in anterior cingulate cortex

Evaluation often involves integrating multiple determinants of value, such as the different possible outcomes in risky choice. A brain region can be placed either before or after a presumed evaluation stage by measuring how responses of its neurons depend on multiple determinants of value. A brain region could also, in principle, show partial integration, which would indicate that it occupies a middle position between (preevaluative) nonintegration and (postevaluative) full integration. Existing mathematical techniques cannot distinguish full from partial integration and therefore risk misidentifying regional function. Here we use a new Bayesian regression-based approach to analyze responses of neurons in dorsal anterior cingulate cortex (dACC) to risky offers. We find that dACC neurons only partially integrate across outcome dimensions, indicating that dACC cannot be assigned to either a pre- or postevaluative position. Neurons in dACC also show putative signatures of value comparison, thereby demonstrating that comparison does not require complete evaluation before proceeding. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Nerve injury alters restraint-induced activation of the basolateral amygdala in male rats

The amygdala is critical for the production of appropriate responses towards emotional or stressful stimuli. It has a characteristic neuronal activation pattern to acute stressors. Chronic pain and acute stress have each been shown to independently modulate the activity of the amygdala. Few studies have investigated the effect of pain or injury, on amygdala activation to acute stress. This study investigated the effects of a neuropathic injury on the activation response of the amygdala to an acute restraint stress. Chronic constriction injury of the right sciatic nerve (CCI) was used to create neuropathic injury and a single brief 15-min acute restraint was used as an emotional/psychological stressor. All rats received cholera toxin B (CTB) retrograde tracer injections into the medial prefrontal cortex (mPFC) to assess if the amygdala to mPFC pathway was specifically regulated by the combination of neuropathic injury and acute stress. To assess differential patterns of activity in amygdala subregions, cFos expression was used as a marker for "acute", restraint triggered neuronal activation, and FosB/ΔFosB expression was used to reveal prolonged neuronal activation/sensitisation triggered by CCI. Restraint resulted in a characteristic increase in cFos expression in the medial amygdala, which was not altered by CCI. Rats with a CCI showed increased cFos expression in the basolateral amygdala (BLA), in response to an acute restraint stress, but not in neurons projecting to the prefrontal cortex. Further, CCI rats showed an increase in FosB/ΔFosB expression which was exclusive to the BLA. This increase likely reflects sensitisation of the BLA as a consequence of nerve injury which may contribute to heightened sensitivity of BLA neurons to acute emotional/ psychological stressors.

Investigation of the Role of Anxiety and Depression on the Formation of Phantom Vibration and Ringing Syndrome Caused by Working Stress during Medical Internship

Phantom vibration syndrome (PVS) and phantom ringing syndrome (PRS) are prevalent hallucinations during medical internship. Depression and anxiety are probably understudied risk factors of PVS and PRS. The aim was to evaluate the role of anxiety and depression on the relationship between working stress during medical internship and PVS and PRS. A prospective longitudinal study, consisted of 74 medical interns, was carried out. The severity of phantom vibrations and ringing, as well as anxiety and depression as measured before, at the third, sixth, and 12th month during internship, and two weeks after internship. We conducted a causal mediation analysis to quantify the role of depression and in the mechanism of working stress during medical internship inducing PVS and PRS. The results showed that depression explained 21.9% and 8.4% for stress-induced PRS and PVS, respectively. In addition, anxiety explained 15.0% and 7.8% for stress-induced PRS and PVS, respectively. Our findings showed both depression and anxiety can explain a portion of stress-induced PVS and PRS during medical internship and might be more important in clinical practice and benefit to prevention of work-related burnout.

The role of norepinephrine in the pathophysiology of schizophrenia

Several lines of evidence have suggested for decades a role for norepinephrine (NE) in the pathophysiology and treatment of schizophrenia. Recent experimental findings reveal anatomical and physiological properties of the locus coeruleus-norepinephrine (LC-NE) system and its involvement in brain function and cognition. Here, we integrate these two lines of evidence. First, we review the functional and structural properties of the LC-NE system and its impact on functional brain networks, cognition, and stress, with special emphasis on recent experimental and theoretical advances. Subsequently, we present an update about the role of LC-associated functions for the pathophysiology of schizophrenia, focusing on the cognitive and motivational deficits. We propose that schizophrenia phenomenology, in particular cognitive symptoms, may be explained by an abnormal interaction between genetic susceptibility and stress-initiated LC-NE dysfunction. This in turn, leads to imbalance between LC activity modes, dysfunctional regulation of brain network integration and neural gain, and deficits in cognitive functions. Finally, we suggest how recent development of experimental approaches can be used to characterize LC function in schizophrenia.

Dopamine neurons do not constitute an obligatory stage in the final common path for the evaluation and pursuit of brain stimulation reward

The neurobiological study of reward was launched by the discovery of intracranial self-stimulation (ICSS). Subsequent investigation of this phenomenon provided the initial link between reward-seeking behavior and dopaminergic neurotransmission. We re-evaluated this relationship by psychophysical, pharmacological, optogenetic, and computational means. In rats working for direct, optical activation of midbrain dopamine neurons, we varied the strength and opportunity cost of the stimulation and measured time allocation, the proportion of trial time devoted to reward pursuit. We found that the dependence of time allocation on the strength and cost of stimulation was similar formally to that observed when electrical stimulation of the medial forebrain bundle served as the reward. When the stimulation is strong and cheap, the rats devote almost all their time to reward pursuit; time allocation falls off as stimulation strength is decreased and/or its opportunity cost is increased. A 3D plot of time allocation versus stimulation strength and cost produces a surface resembling the corner of a plateau (the “reward mountain”). We show that dopamine-transporter blockade shifts the mountain along both the strength and cost axes in rats working for optical activation of midbrain dopamine neurons. In contrast, the same drug shifted the mountain uniquely along the opportunity-cost axis when rats worked for electrical MFB stimulation in a prior study. Dopamine neurons are an obligatory stage in the dominant model of ICSS, which positions them at a key nexus in the final common path for reward seeking. This model fails to provide a cogent account for the differential effect of dopamine transporter blockade on the reward mountain. Instead, we propose that midbrain dopamine neurons and neurons with non-dopaminergic, MFB axons constitute parallel limbs of brain-reward circuitry that ultimately converge on the final-common path for the evaluation and pursuit of rewards.

In search of a definition of reinforcer value: Some successes and failures of the multiplicative hyperbolic model

The concept of 'value' has enjoyed a central position in many theoretical accounts of choice behaviour. Several definitions of 'value' are contrasted in this paper, and one particular approach is defended, whereby value is defined as a dimensionless intervening variable. This definition is a cornerstone of the multiplicative hyperbolic model of choice (MHM), which was proposed twenty years ago as a modification of Mazur's (1987) hyperbolic model of delay discounting. This paper reviews some of the merits and shortcomings of MHM, and suggests some ways in which MHM might be extended and improved. A formal link between 'value' and the related concept of 'response strength' is suggested, and revisions of the model are proposed which may enable it to accommodate several behavioural phenomena not considered in the original formulation. Broadening the scope of MHM comes at the cost of adding to its burden of free parameters, and it is emphasised that addition of any new parameters needs empirical justification. The status of value as a dimensionless intervening variable is upheld; however it is noted that a growing body of empirical evidence for links between neurobiological phenomena and value suggests that interpretation of value as a hypothetical construct may be warranted.

Motivational goal-priming with or without awareness produces faster and stronger force exertion

Previous research has demonstrated that barely visible (subliminal) goal-priming with motivational reward can alter the state of the motor system and enhance motor output. Research shows that these affective-motivational effects result from associations between goal representations and positive affect without conscious awareness. Here, we tested whether motivational priming can increase motor output even if the priming is fully visible (supraliminal), and whether the priming effect occurs through increased cortical excitability. Groups of participants were primed with either barely visible or fully visible words related to effort and control sequences of random letters that were each followed by fully visible positively reinforcing words. The priming effect was measured behaviourally by handgrip force and reaction time to the grip cue after the priming was complete. Physiologically, the effects were measured by pupil dilation and motor-evoked potentials (MEPs) in response to transcranial magnetic stimulation during the priming task. Analysis showed that for both the supraliminal and subliminal conditions, reaction time decreased and total force, MEP magnitude, and pupil dilation increased. None of the priming-induced changes in behaviour or physiology differed significantly between the supraliminal and the subliminal groups, indicating that implicit motivation towards motor goals might not require conscious perception of the goals.

Mice learn to avoid regret

Regret can be defined as the subjective experience of recognizing that one has made a mistake and that a better alternative could have been selected. The experience of regret is thought to carry negative utility. This typically takes two distinct forms: augmenting immediate postregret valuations to make up for losses, and augmenting long-term changes in decision-making strategies to avoid future instances of regret altogether. While the short-term changes in valuation have been studied in human psychology, economics, neuroscience, and even recently in nonhuman-primate and rodent neurophysiology, the latter long-term process has received far less attention, with no reports of regret avoidance in nonhuman decision-making paradigms. We trained 31 mice in a novel variant of the Restaurant Row economic decision-making task, in which mice make decisions of whether to spend time from a limited budget to achieve food rewards of varying costs (delays). Importantly, we tested mice longitudinally for 70 consecutive days, during which the task provided their only source of food. Thus, decision strategies were interdependent across both trials and days. We separated principal commitment decisions from secondary reevaluation decisions across space and time and found evidence for regret-like behaviors following change-of-mind decisions that corrected prior economically disadvantageous choices. Immediately following change-of-mind events, subsequent decisions appeared to make up for lost effort by altering willingness to wait, decision speed, and pellet consumption speed, consistent with past reports of regret in rodents. As mice were exposed to an increasingly reward-scarce environment, we found they adapted and refined distinct economic decision-making strategies over the course of weeks to maximize reinforcement rate. However, we also found that even without changes in reinforcement rate, mice transitioned from an early strategy rooted in foraging to a strategy rooted in deliberation and planning that prevented future regret-inducing change-of-mind episodes from occurring. These data suggest that mice are learning to avoid future regret, independent of and separate from reinforcement rate maximization.

Regret describes a unique postdecision phenomenon in which losses are realized as a fault of one’s own actions. Regret is often hypothesized to have an inherent negative utility, and humans will often incur costs so as to avoid the risk of future regret. However, current models of nonhuman decision-making are based on reward maximization hypotheses. We recently found that rats express regret behaviorally and neurophysiologically on neuroeconomic foraging tasks; however, it remains unknown whether nonhuman animals will change strategies so as to avoid regret, even in the absence of changes in the achieved rate of reinforcement. Here, we provide the first evidence that mice change strategies to avoid future regret, independent of and separate from reinforcement rate maximization. Our data suggest mice accomplish this by shifting from a foraging decision-making strategy that produces change-of-mind decisions after investment mistakes to one rooted in deliberation that learns to plan ahead.

Neural encoding of choice during a delayed response task in primate striatum and orbitofrontal cortex

Reward outcomes are available in many diverse situations and all involve choice. If there are multiple outcomes each rewarding, then decisions regarding relative value lead to choosing one over another. Important factors related to choice context should be encoded and utilized for this form of adaptive choosing. These factors can include the number of alternatives, the pacing of choice behavior and the possibility to reverse one's choice. An essential step in understanding if the context of choice is encoded is to directly compare choice with a context in which choice is absent. Neural activity in orbitofrontal cortex and striatum encodes potential value parameters related to reward quality and quantity as well as relative preference. We examined how neural activations in these brain regions are sensitive to choice situations and potentially involved in a prediction for the upcoming outcome selection. Neural activity was recorded and compared between a two-choice spatial delayed response task and an imperative 'one-option' task. Neural activity was obtained that extended from the instruction cue to the movement similar to previous work utilizing the identical imperative task. Orbitofrontal and striatal neural responses depended upon the decision about the choice of which reward to collect. Moreover, signals to predictive instruction cues that precede choice were selective for the choice situation. These neural responses could reflect chosen value with greater information on relative value of individual options as well as encode choice context itself embedded in the task as a part of the post-decision variable.

The network architecture of value learning

Value guides behavior. With knowledge of stimulus values and action consequences, behaviors that maximize expected reward can be selected. Prior work has identified several brain structures critical for representing both stimuli and their values. Yet, it remains unclear how these structures interact with one another and with other regions of the brain to support the dynamic acquisition of value-related knowledge. Here, we use a network neuroscience approach to examine how BOLD functional networks change as 20 healthy human subjects learn the values of novel visual stimuli over the course of four consecutive days. We show that connections between regions of the visual, frontal, and cingulate cortices become stronger as learning progresses, with some of these changes being specific to the type of feedback received during learning. These results demonstrate that functional networks dynamically track behavioral improvement in value judgments, and that interactions between network communities form predictive biomarkers of learning.

Rational human behavior is the pursuit of actions that maximize expected reward. These rewards can be understood as stimulus-value contingencies, learned by experience throughout our lives. Various structures have been recognized to participate in these learning processes. Yet, an understanding of how these structures interact with one another and with other brain regions remains vastly unexplored. Here, we propose a novel analytical framework utilizing and extending techniques from the dynamic network neuroscience to ask “How do our brains change when we learn values?” We find that interactions between sensory and fronto-cingulate structures grow stronger as learning progresses, bringing together several isolated findings in the cognitive neuroscience of value-based behavior and extending our understanding of human learning in general.

Valuation of opportunity costs by rats working for rewarding electrical brain stimulation

Pursuit of one goal typically precludes simultaneous pursuit of another. Thus, each exclusive activity entails an “opportunity cost:” the forgone benefits from the next-best activity eschewed. The present experiment estimates, in laboratory rats, the function that maps objective opportunity costs into subjective ones. In an operant chamber, rewarding electrical brain stimulation was delivered when the cumulative time a lever had been depressed reached a criterion duration. The value of the activities forgone during this duration is the opportunity cost of the electrical reward. We determined which of four functions best describes how objective opportunity costs, expressed as the required duration of lever depression, are translated into their subjective equivalents. The simplest account is the identity function, which equates subjective and objective opportunity costs. A variant of this function called the “sigmoidal-slope function,” converges on the identity function at longer durations but deviates from it at shorter durations. The sigmoidal-slope function has the form of a hockey stick. The flat “blade” denotes a range over which opportunity costs are subjectively equivalent; these durations are too short to allow substitution of more beneficial activities. The blade extends into an upward-curving portion over which costs become discriminable and finally into the straight “handle,” over which objective and subjective costs match. The two remaining functions are based on hyperbolic and exponential temporal discounting, respectively. The results are best described by the sigmoidal-slope function. That this is so suggests that different principles of intertemporal choice are involved in the evaluation of time spent working for a reward or waiting for its delivery. The subjective opportunity-cost function plays a key role in the evaluation and selection of goals. An accurate description of its form and parameters is essential to successful modeling and prediction of instrumental performance and reward-related decision making.

It's all in the type of the task: Dopamine modulates kinematic patterns during competitive vs. cooperative interaction in Parkinson's disease

Increasing evidence suggests that a dysfunctional dopaminergic system affects the ability to socially interact. Since Parkinson's disease (PD) provides a model for assessing dopaminergic dysfunctions in humans, our study was designed to investigate social interactions in PD patients receiving dopamine replacement therapy (Levodopa=l-Dopa) and in neurologically healthy controls. We focused on the kinematics of one action, reaching to grasp a wooden block, which was performed within the context of two basic modes of social cognition, namely cooperation and competition. During the cooperative tasks, two participants were instructed to reach and grasp their respective objects and to cooperate in forming a specific configuration on the working table. During the competitive tasks, two participants were instructed to compete to place their own object at the bottom of a tower to be built on the working table. PD patients' ability to modulate motor patterning depending on the intention motivating the action they were about to perform was evaluated in both "on" (with l-Dopa) and "off" (without l-Dopa) states. Study results revealed that both the healthy controls and the 'on' PD patients had distinct kinematic patterns for cooperative and competitive actions and that these differed from patterns mirroring similar actions performed by those same participants in non social conditions. The kinematic patterns of the healthy controls and the 'on' patients were highly correlated during the cooperative tasks. The 'off' PD patients were, instead, unable to differentiate between isolated and social conditions. These results support the hypothesis that dopaminergic neurotransmission is involved in shaping the mechanisms underlying social interactions.

Are Emotions Natural Kinds?

Laypeople and scientists alike believe that they know anger, or sadness, or fear, when they see it. These emotions and a few others are presumed to have specific causal mechanisms in the brain and properties that are observable (on the face, in the voice, in the body, or in experience)—that is, they are assumed to be natural kinds. If a given emotion is a natural kind and can be identified objectively, then it is possible to make discoveries about that emotion. Indeed, the scientific study of emotion is founded on this assumption. In this article, I review the accumulating empirical evidence that is inconsistent with the view that there are kinds of emotion with boundaries that are carved in nature. I then consider what moving beyond a natural-kind view might mean for the scientific understanding of emotion.

Toward a systems-oriented approach to the role of the extended amygdala in adaptive responding

Research into the structure and function of the basal forebrain macrostructure called the extended amygdala (EA) has recently seen considerable growth. This paper reviews that work, with the objectives of identifying underlying themes and developing a common goal towards which investigators of EA function might work. The paper begins with a brief review of the structure and the ontological and phylogenetic origins of the EA. It continues with a review of research into the role of the EA in both aversive and appetitive states, noting that these two seemingly disparate avenues of research converge on the concept of reinforcement - either negative or positive - of adaptive responding. These reviews lead to a proposal as to where the EA may fit in the organization of the basal forebrain, and an invitation to investigators to place their findings in a unifying conceptual framework of the EA as a collection of neural ensembles that mediate adaptive responding.

The Cognitive Neuroscience of Human Decision Making: A Review and Conceptual Framework

Decision making, the process of choosing between options, is a fundamental human behavior that has been studied intensively by disciplines ranging from cognitive psychology to economics. Despite the importance of this behavior, the neural substrates of decision making are only beginning to be understood. Impaired decision making is recognized in neuropsychiatric conditions such as dementia and drug addiction, and the inconsistencies and biases of healthy decision makers have been intensively studied. However, the tools of cognitive neuroscience have only recently been applied to understanding the brain basis of this complex behavior. This article reviews the literature on the cognitive neuroscience of human decision making, focusing on the roles of the frontal lobes, and provides a conceptual framework for organizing this disparate body of work.

The neural substrates for the rewarding and dopamine-releasing effects of medial forebrain bundle stimulation have partially discrepant frequency responses

Midbrain dopamine neurons have long been implicated in the rewarding effect produced by electrical brain stimulation of the medial forebrain bundle (MFB). These neurons are excited trans-synaptically, but their precise role in intracranial self-stimulation (ICSS) has yet to be determined. This study assessed the hypothesis that midbrain dopamine neurons are in series with the directly stimulated substrate for self-stimulation of the MFB and either perform spatio-temporal integration of synaptic input from directly activated MFB fibers or relay the results of such integration to efferent stages of the reward circuitry. Psychometric current-frequency trade-off functions were derived from ICSS performance, and chemometric trade-off functions were derived from stimulation-induced dopamine transients in the nucleus accumbens (NAc) shell, measured by means of fast-scan cyclic voltammetry. Whereas the psychometric functions decline monotonically over a broad range of pulse frequencies and level off only at high frequencies, the chemometric functions obtained with the same rats and electrodes are either U-shaped or level off at lower pulse frequencies. This discrepancy was observed when the dopamine transients were recorded in either anesthetized or awake subjects. The lack of correspondence between the psychometric and chemometric functions is inconsistent with the hypothesis that dopamine neurons projecting to the NAc shell constitute an entire series stage of the neural circuit subserving self-stimulation of the MFB.

Psychophysical inference of frequency-following fidelity in the neural substrate for brain stimulation reward

The rewarding effect of electrical brain stimulation has been studied extensively for 60 years, yet the identity of the underlying neural circuitry remains unknown. Previous experiments have characterized the directly stimulated ("first-stage") neurons implicated in self-stimulation of the medial forebrain bundle. Their properties are consistent with those of fine, myelinated axons, at least some of which project rostro-caudally. These properties do not match those of dopaminergic neurons. The present psychophysical experiment estimates an additional first-stage characteristic: maximum firing frequency. We test a frequency-following model that maps the experimenter-set pulse frequency into the frequency of firing induced in the directly stimulated neurons. As pulse frequency is increased, firing frequency initially increases at the same rate, then becomes probabilistic, and finally levels off. The frequency-following function is based on the counter model which holds that the rewarding effect of a pulse train is determined by the aggregate spike rate triggered in first-stage neurons during a given interval. In 7 self-stimulating rats, we measured current- vs. pulse-frequency trade-off functions. The trade-off data were well described by the frequency-following model, and its upper asymptote was approached at a median value of 360 Hz (IQR = 46 Hz). This value implies a highly excitable, non-dopaminergic population of first-stage neurons. Incorporating the frequency-following function and parameters in Shizgal's 3-dimensional reward-mountain model improves its accuracy and predictive power.

Social intentions in Parkinson's disease patients: A kinematic study

Dysfunction of the dopaminergic system leads to motor, cognitive and motivational symptoms in brain disorders such as Parkinson's disease (PD). Moreover, the dopaminergic system plays an important role in social interactions. The dopaminergic input to the basal ganglia (BG) thought to integrate social cues during the planning and execution of voluntary movements remains, however, largely unexplored. Since PD provides a model to assess this function in humans, our study aimed to investigate the effects of social intentions on actions in non-demented PDpatients receiving dopamine replacement therapy (Levodopa = l-Dopa) and in neurologically healthy control participants. Patients' ability to modulate motor patterning depending on the intention motivating the action to be performed was evaluated both in "on" (with l-Dopa) and "off" (without l-Dopa) states. Participants were instructed to reach for and to grasp an object; they were then told to hand it to another person (social condition) or to place it on a concave frame (individual condition). A 'passive-observer' condition, which was similar to the 'individual' condition except for the presence of an onlooker who simply observed the scene, was also assessed to exclude the possibility that differences might be due to the presence of another person. Movement kinematics were recorded using a three-dimensional motion analysis system. Study results demonstrated that the controls and the PD patients in an 'on' state adopted different kinematic patterning for the 'social' and the 'individual' conditions; the PD patients in the 'off' state, instead, were unable to kinematically differentiate between the two conditions. These results suggest that l-Dopa treatment has positive effects on translating social intentions into specific motor patterns in PD patients.

Decision making: the neuroethological turn

Neuroeconomics applies models from economics and psychology to inform neurobiological studies of choice. This approach has revealed neural signatures of concepts like value, risk, and ambiguity, which are known to influence decision making. Such observations have led theorists to hypothesize a single, unified decision process that mediates choice behavior via a common neural currency for outcomes like food, money, or social praise. In parallel, recent neuroethological studies of decision making have focused on natural behaviors like foraging, mate choice, and social interactions. These decisions strongly impact evolutionary fitness and thus are likely to have played a key role in shaping the neural circuits that mediate decision making. This approach has revealed a suite of computational motifs that appear to be shared across a wide variety of organisms. We argue that the existence of deep homologies in the neural circuits mediating choice may have profound implications for understanding human decision making in health and disease.

Orquestic regulation of neurotransmitters on reward-seeking behavior

The ventral tegmental area is strongly associated with the reward system. Dopamine is released in areas such as the nucleus accumbens and prefrontal cortex as a result of rewarding experiences such as food, sex, and neutral stimuli that become associated with them. Electrical stimulation of the ventral tegmental area or its output pathways can itself serve as a potent reward. Different drugs that increase dopamine levels are intrinsically rewarding. Although the dopaminergic system represent the cornerstone of the reward system, other neurotransmitters such as endogenous opioids, glutamate, γ-Aminobutyric acid, acetylcholine, serotonin, adenosine, endocannabinoids, orexins, galanin and histamine all affect this mesolimbic dopaminergic system. Consequently, genetic variations of neurotransmission are thought influence reward processing that in turn may affect distinctive social behavior and susceptibility to addiction. Here, we discuss current evidence on the orquestic regulation of different neurotranmitters on reward-seeking behavior and its potential effect on drug addiction.

Distinguishing informational from value-related encoding of rewarding and punishing outcomes in the human brain

There is accumulating evidence implicating a set of key brain regions in encoding rewarding and punishing outcomes, including the orbitofrontal cortex, medial prefrontal cortex, ventral striatum, anterior insula, and anterior cingulate. However, it has proved challenging to reach consensus concerning the extent to which different brain areas are involved in differentially encoding rewarding and punishing outcomes. Here, we show that many of the brain areas involved in outcome processing represent multiple outcome components: encoding the value of outcomes (whether rewarding or punishing) and informational coding, i.e. signaling whether a given outcome is rewarding or punishing, ignoring magnitude or experienced utility. In particular, we report informational signals in the lateral orbitofrontal cortex and anterior insular cortex that respond to both rewarding and punishing feedback, even though value-related signals in these areas appear to be selectively driven by punishing feedback. These findings highlight the importance of taking into account features of outcomes other than value when characterising the contributions of different brain regions in outcome processing.

A new view of the effect of dopamine receptor antagonism on operant performance for rewarding brain stimulation in the rat

RATIONALE

Previous studies of neuroleptic challenges to intracranial self-stimulation (ICSS) employed two-dimensional (2D) measurements (curve shifts). Results so obtained are ambiguous with regard to the stage of neural processing at which the drug produces its performance-altering effect. We substituted a three-dimensional (3D) method that measures reward-seeking as a function of both the strength and cost of reward. This method reveals whether changes in reward seeking are due to drug action prior to the output of the circuitry that performs spatiotemporal integration of the stimulation-induced neural activity.

OBJECTIVES

The aim of this study was to obtain new information about the stage of neural processing at which pimozide acts to alter pursuit of brain stimulation reward (BSR).

METHODS

Following treatment with pimozide (0.1 mg/kg) or its vehicle, the proportion of trial time allocated to working for BSR was measured as a function of pulse frequency and opportunity cost. A surface defined by Shizgal's reward-mountain model was fitted to the drug and vehicle data.

RESULTS

Pimozide lowered the cost required to decrease performance for a maximal BSR to half its maximal level but did not alter the pulse-frequency required to produce a reward of half-maximal intensity.

CONCLUSIONS

Like indirect dopamine agonists, pimozide does not alter the sensitivity of brain reward circuity but changes reward-system gain, subjective effort costs, and/or the value of activities that compete with ICSS. The 3D method is more sensitive and informative than the 2D methods employed previously.

Validation and extension of the reward-mountain model

The reward-mountain model relates the vigor of reward seeking to the strength and cost of reward. Application of this model provides information about the stage of processing at which manipulations such as drug administration, lesions, deprivation states, and optogenetic interventions act to alter reward seeking. The model has been updated by incorporation of new information about frequency following in the directly stimulated neurons responsible for brain stimulation reward and about the function that maps objective opportunity costs into subjective ones. The behavioral methods for applying the model have been updated and improved as well. To assess the impact of these changes, two related predictions of the model that were supported by earlier work have been retested: (1) altering the duration of rewarding brain stimulation should change the pulse frequency required to produce a reward of half-maximal intensity, and (2) this manipulation should not change the opportunity cost at which half-maximal performance is directed at earning a maximally intense reward. Prediction 1 was supported in all six subjects, but prediction 2 was supported in only three. The latter finding is interpreted to reflect recruitment, at some stimulation sites, of a heterogeneous reward substrate comprising dual, parallel circuits that integrate the stimulation-induced neural signals.

A dimensional approach to the phantom vibration and ringing syndrome during medical internship

Phantom vibrations and ringing of mobile phones are prevalent hallucinations in the general population. They might be considered as a "normal" brain mechanism. The aim of this study was to determine if a dimensional approach to identify individuals suffering from these hallucinations was more important than a categorical approach. A prospective longitudinal study of 74 medical interns (male: 46, mean age: 24.8 ± 1.2) was carried out using repeated investigations of the severity of phantom vibrations and ringing, as well as accompanying symptoms of anxiety and depression as measured by Beck Anxiety Inventory (BAI) and the Beck Depression Inventory (BDI) before, at the 3rd, 6th, and 12th month during internship, and 2 weeks after internship. We utilized the cognitive and somatic subscales of the BDI, as well as the subjective, somatic and panic subscales of the BAI. The correlation between phantom vibration and ringing was lowest before the internship but became moderate during the internship and high 2 weeks after it. Compared to interns with subclinical phantom ringing and vibrations, interns with severe phantom vibrations and ringing had higher subjective and somatic anxiety and somatic depressive scores at any time point throughout the internship. Only interns with severe phantom ringing had more cognitive/affective depression. A dimensional approach to the phantom vibration and ringing syndrome is a powerful way to identify their correlation, as well as their association with anxiety and depression.

Impact of contour on aesthetic judgments and approach-avoidance decisions in architecture

On average, we urban dwellers spend about 90% of our time indoors, and share the intuition that the physical features of the places we live and work in influence how we feel and act. However, there is surprisingly little research on how architecture impacts behavior, much less on how it influences brain function. To begin closing this gap, we conducted a functional magnetic resonance imaging study to examine how systematic variation in contour impacts aesthetic judgments and approach-avoidance decisions, outcome measures of interest to both architects and users of spaces alike. As predicted, participants were more likely to judge spaces as beautiful if they were curvilinear than rectilinear. Neuroanatomically, when contemplating beauty, curvilinear contour activated the anterior cingulate cortex exclusively, a region strongly responsive to the reward properties and emotional salience of objects. Complementing this finding, pleasantness--the valence dimension of the affect circumplex--accounted for nearly 60% of the variance in beauty ratings. Furthermore, activation in a distributed brain network known to underlie the aesthetic evaluation of different types of visual stimuli covaried with beauty ratings. In contrast, contour did not affect approach-avoidance decisions, although curvilinear spaces activated the visual cortex. The results suggest that the well-established effect of contour on aesthetic preference can be extended to architecture. Furthermore, the combination of our behavioral and neural evidence underscores the role of emotion in our preference for curvilinear objects in this domain.

Prevalent hallucinations during medical internships: phantom vibration and ringing syndromes

BACKGROUND

Phantom vibration syndrome is a type of hallucination reported among mobile phone users in the general population. Another similar perception, phantom ringing syndrome, has not been previously described in the medical literature.

METHODS

A prospective longitudinal study of 74 medical interns (46 males, 28 females; mean age, 24.8±1.2 years) was conducted using repeated investigations of the prevalence and associated factors of phantom vibration and ringing. The accompanying symptoms of anxiety and depression were evaluated with the Beck Anxiety and Depression Inventories before the internship began, and again at the third, sixth, and twelfth internship months, and two weeks after the internship ended.

RESULTS

The baseline prevalence of phantom vibration was 78.1%, which increased to 95.9% and 93.2% in the third and sixth internship months. The prevalence returned to 80.8% at the twelfth month and decreased to 50.0% 2 weeks after the internship ended. The baseline prevalence of phantom ringing was 27.4%, which increased to 84.9%, 87.7%, and 86.3% in the third, sixth, and twelfth internship months, respectively. This returned to 54.2% two weeks after the internship ended. The anxiety and depression scores also increased during the internship, and returned to baseline two weeks after the internship. There was no significant correlation between phantom vibration/ringing and symptoms of anxiety or depression. The incidence of both phantom vibration and ringing syndromes significantly increased during the internship, and subsequent recovery.

CONCLUSION

This study suggests that phantom vibration and ringing might be entities that are independent of anxiety or depression during evaluation of stress-associated experiences during medical internships.

Role of dopamine tone in the pursuit of brain stimulation reward

Dopaminergic neurons contribute to intracranial self-stimulation (ICSS) and other reward-seeking behaviors, but it is not yet known where dopaminergic neurons intervene in the neural circuitry underlying reward pursuit or which psychological processes are involved. In rats working for electrical stimulation of the medial forebrain bundle, we assessed the effect of GBR-12909 (1-[2-[bis(4-fluorophenyl)-methoxy]ethyl]-4-[3- phenylpropyl]piperazine), a specific blocker of the dopamine transporter. Operant performance was measured as a function of the strength and cost of electrical stimulation. GBR-12909 increased the opportunity cost most subjects were willing to pay for a reward of a given intensity. However, this effect was smaller than that produced by a regimen of cocaine administration that drove similar increases in nucleus accumbens (NAc) dopamine levels in unstimulated rats. Delivery of rewarding stimulation to drug-treated rats caused an additional increase in dopamine concentration in the NAc shell in cocaine-treated, but not GBR-12909-treated, rats. These behavioral and neurochemical differences may reflect blockade of the norepinephrine transporter by cocaine but not by GBR-12909. Whereas the effect of psychomotor stimulants on ICSS has long been attributed to dopaminergic action at early stages of the reward pathway, the results reported here imply that increased dopamine tone boosts reward pursuit by acting at or beyond the output of the circuitry that temporally and spatially summates the output of the directly stimulated neurons underlying ICSS. The observed enhancement of reward seeking could be attributable to a decrease in the value of competing behaviors, a decrease in subjective effort costs, or an increase in reward-system gain.

Neuroeconomics and the study of addiction

We review the key findings in the application of neuroeconomics to the study of addiction. Although there are not "bright line" boundaries between neuroeconomics and other areas of behavioral science, neuroeconomics coheres around the topic of the neural representations of "Value" (synonymous with the "decision utility" of behavioral economics). Neuroeconomics parameterizes distinct features of Valuation, going beyond the general construct of "reward sensitivity" widely used in addiction research. We argue that its modeling refinements might facilitate the identification of neural substrates that contribute to addiction. We highlight two areas of neuroeconomics that have been particularly productive. The first is research on neural correlates of delay discounting (reduced Valuation of rewards as a function of their delay). The second is work that models how Value is learned as a function of "prediction-error" signaling. Although both areas are part of the neuroeconomic program, delay discounting research grows directly out of behavioral economics, whereas prediction-error work is grounded in models of learning. We also consider efforts to apply neuroeconomics to the study of self-control and discuss challenges for this area. We argue that neuroeconomic work has the potential to generate breakthrough research in addiction science.

Neuroeconomics: a bridge for translational research

Neuroeconomic methods combine behavioral economic experiments to parameterize aspects of reward-related decision-making with neuroimaging techniques to record corresponding brain activity. In this introductory article to the current special issue, we propose that neuroeconomics is a potential bridge for translational research in psychiatry for several reasons. First, neuroeconomics-derived theoretical predictions about optimal adaptation in a changing environment provide an objective metric to examine psychopathology. Second, neuroeconomics provides a "multilevel" research approach that combines performance (behavioral) measures with intermediate measures between behavior and neurobiology (e.g., neuroimaging) and uses a common metaphor to describe decision-making across multiple levels of explanation. As such, ecologically valid behavioral paradigms closely mirror the physical mechanisms of reward processing. Third, neuroeconomics provides a platform for investigators from neuroscience, economics, psychiatry, and social and clinical psychology to develop a common language for studying reward-related decision making in psychiatric disorders. Therefore, neuroeconomics can provide promising candidate endophenotypes that might help clarify the basis of high heritability associated with psychiatric disorders and that might, in turn, inform treatment.

Scarce means with alternative uses: robbins' definition of economics and its extension to the behavioral and neurobiological study of animal decision making

Almost 80 years ago, Lionel Robbins proposed a highly influential definition of the subject matter of economics: the allocation of scarce means that have alternative ends. Robbins confined his definition to human behavior, and he strove to separate economics from the natural sciences in general and from psychology in particular. Nonetheless, I extend his definition to the behavior of non-human animals, rooting my account in psychological processes and their neural underpinnings. Some historical developments are reviewed that render such a view more plausible today than would have been the case in Robbins’ time. To illustrate a neuroeconomic perspective on decision making in non-human animals, I discuss research on the rewarding effect of electrical brain stimulation. Central to this discussion is an empirically based, functional/computational model of how the subjective intensity of the electrical reward is computed and combined with subjective costs so as to determine the allocation of time to the pursuit of reward. Some successes achieved by applying the model are discussed, along with limitations, and evidence is presented regarding the roles played by several different neural populations in processes posited by the model. I present a rationale for marshaling convergent experimental methods to ground psychological and computational processes in the activity of identified neural populations, and I discuss the strengths, weaknesses, and complementarity of the individual approaches. I then sketch some recent developments that hold great promise for advancing our understanding of structure–function relationships in neuroscience in general and in the neuroeconomic study of decision making in particular.

A molecular diffusion based utility model for Drosophila larval phototaxis

Background

Generally, utility based decision making models focus on experimental outcomes. In this paper we propose a utility model based on molecular diffusion to simulate the choice behavior of Drosophila larvae exposed to different light conditions.

Methods

In this paper, light/dark choice-based Drosophila larval phototaxis is analyzed with our molecular diffusion based model. An ISCEM algorithm is developed to estimate the model parameters.

Results

By applying this behavioral utility model to light intensity and phototaxis data, we show that this model fits the experimental data very well.

Conclusions

Our model provides new insights into decision making mechanisms in general. From an engineering viewpoint, we propose that the model could be applied to a wider range of decision making practices.

Why we should use animals to study economic decision making - a perspective

Despite the rich tradition in psychology and biology, animals as research subjects have never gained a similar acceptance in microeconomics research. With this article, we counter this trend of negligence and try to convey the message that animal models are an indispensible complement to the literature on human economic decision making. This perspective review departs from a description of the similarities in economic and evolutionary theories of human and animal decision making, with particular emphasis on the optimality aspect that both classes of theories have in common. In a second part, we outline that actual, empirically observed decisions often do not conform to the normative ideals of economic and ecological models, and that many of the behavioral violations found in humans can also be found in animals. In a third part, we make a case that the sense or nonsense of the behavioral violations of optimality principles in humans can best be understood from an evolutionary perspective, thus requiring animal research. Finally, we conclude with a critical discussion of the parallels and inherent differences in human and animal research.

Cannabinoid receptor blockade reduces the opportunity cost at which rats maintain operant performance for rewarding brain stimulation

There is ample evidence that blockade of CB(1) receptors reduces reward seeking. However, the reported effects of CB(1) blockade on performance for rewarding electrical brain stimulation stand out as an exception. By applying a novel method for conceptualizing and measuring reward seeking, we show that AM-251, a CB(1) receptor antagonist, does indeed decrease performance for rewarding electrical stimulation of the medial forebrain bundle in rats. Reward seeking depends on multiple sets of variables, including the intensity of the reward, its cost, and the value of competing rewards. In turn, reward intensity depends both on the sensitivity and gain of brain reward circuitry. We show that drug-induced changes in sensitivity cannot account for the suppressive effect of AM-251 on reward seeking. Therefore, the role of CB(1) receptors must be sought among the remaining determinants of performance. Our analysis provides an explanation of the inconsistencies between prior reports, which likely arose from the following: (1) the averaging of data across subjects showing heterogeneous effects and (2) the use of methods that cannot distinguish between the different determinants of reward pursuit. By means of microdialysis, we demonstrate that blockade of CB(1) receptors attenuates nucleus accumbens dopamine release in response to rewarding medial forebrain bundle stimulation, and we propose that this action is responsible for the ability of the drug to decrease performance for the electrical reward.

At what stage of neural processing does cocaine act to boost pursuit of rewards?

Dopamine-containing neurons have been implicated in reward and decision making. One element of the supporting evidence is that cocaine, like other drugs that increase dopaminergic neurotransmission, powerfully potentiates reward seeking. We analyze this phenomenon from a novel perspective, introducing a new conceptual framework and new methodology for determining the stage(s) of neural processing at which drugs, lesions and physiological manipulations act to influence reward-seeking behavior. Cocaine strongly boosts the proclivity of rats to work for rewarding electrical brain stimulation. We show that the conventional conceptual framework and methods do not distinguish between three conflicting accounts of how the drug produces this effect: increased sensitivity of brain reward circuitry, increased gain, or decreased subjective reward costs. Sensitivity determines the stimulation strength required to produce a reward of a given intensity (a measure analogous to the K_M of an enzyme) whereas gain determines the maximum intensity attainable (a measure analogous to the v_max of an enzyme-catalyzed reaction). To distinguish sensitivity changes from the other determinants, we measured and modeled reward seeking as a function of both stimulation strength and opportunity cost. The principal effect of cocaine was a two-fourfold increase in willingness to pay for the electrical reward, an effect consistent with increased gain or decreased subjective cost. This finding challenges the long-standing view that cocaine increases the sensitivity of brain reward circuitry. We discuss the implications of the results and the analytic approach for theories of how dopaminergic neurons and other diffuse modulatory brain systems contribute to reward pursuit, and we explore the implications of the conceptual framework for the study of natural rewards, drug reward, and mood.

Dopaminergic reward system: a short integrative review

Memory is an essential element to adaptive behavior since it allows consolidation of past experience guiding the subject to consider them in future experiences. Among the endogenous molecules that participate in the consolidation of memory, including the drug-seeking reward, considered as a form of learning, is dopamine. This neurotransmitter modulates the activity of specific brain nucleus such as nuclei accumbens, putamen, ventral tegmental area (VTA), among others and synchronizes the activity of these nuclei to establish the neurobiological mechanism to set the hedonic element of learning. We review the experimental evidence that highlights the activity of different brain nuclei modulating the mechanisms whereby dopamine biases memory towards events that are of motivational significance.

Dopaminergic reward system: a short integrative review

Memory is an essential element to adaptive behavior since it allows consolidation of past experience guiding the subject to consider them in future experiences. Among the endogenous molecules that participate in the consolidation of memory, including the drug-seeking reward, considered as a form of learning, is dopamine. This neurotransmitter modulates the activity of specific brain nucleus such as nuclei accumbens, putamen, ventral tegmental area (VTA), among others and synchronizes the activity of these nuclei to establish the neurobiological mechanism to set the hedonic element of learning. We review the experimental evidence that highlights the activity of different brain nuclei modulating the mechanisms whereby dopamine biases memory towards events that are of motivational significance.

The unconscious will: how the pursuit of goals operates outside of conscious awareness

People often act in order to realize desired outcomes, or goals. Although behavioral science recognizes that people can skillfully pursue goals without consciously attending to their behavior once these goals are set, conscious will is considered to be the starting point of goal pursuit. Indeed, when we decide to work hard on a task, it feels as if that conscious decision is the first and foremost cause of our behavior. That is, we are likely to say, if asked, that the decision to act produced the actions themselves. Recent discoveries, however, challenge this causal status of conscious will. They demonstrate that under some conditions, actions are initiated even though we are unconscious of the goals to be attained or their motivating effect on our behavior. Here we analyze how goal pursuit can possibly operate unconsciously.

Neural signatures of intransitive preferences

It is often assumed that decisions are made by rank-ordering and thus comparing the available choice options based on their subjective values. Rank-ordering requires that the alternatives’ subjective values are mentally represented at least on an ordinal scale. Because one alternative cannot be at the same time better and worse than another alternative, choices should satisfy transitivity (if alternative A is preferred over B, and B is preferred over C, A should be preferred over C). Yet, individuals often demonstrate striking violations of transitivity (preferring C over A). We used functional magnetic resonance imaging to study the neural correlates of intransitive choices between gambles varying in magnitude and probability of financial gains. Behavioral intransitivities were common. They occurred because participants did not evaluate the gambles independently, but in comparison with the alternative gamble presented. Neural value signals in prefrontal and parietal cortex were not ordinal-scaled and transitive, but reflected fluctuations in the gambles’ local, pairing-dependent preference-ranks. Detailed behavioral analysis of gamble preferences showed that, depending on the difference in the offered gambles’ attributes, participants gave variable priority to magnitude or probability and thus shifted between preferring richer or safer gambles. The variable, context-dependent priority given to magnitude and probability was tracked by insula (magnitude) and posterior cingulate (probability). Their activation-balance may reflect the individual decision rules leading to intransitivities. Thus, the phenomenon of intransitivity is reflected in the organization of the neural systems involved in risky decision-making.

Breeding for pleasure: the value of pleasure and pain in evolution and animal welfare

Farming and laboratory industries face questions about whether to breed animals with altered capacities for pleasure and pain. This paper addresses this issue from different approaches to animal welfare based on experiences, fitness and naturalness. This can illuminate both the breeding-related issues and the different approaches themselves. These differences have practical implications for decisions about animal breeding. All three approaches will agree that pleasure that is adaptive in natural environments has positive value and that maladaptive pain has negative value. However, where animals’ environments will not be natural, experiences-based approaches may support breeding animals that experience more pleasure and less pain or insentient animals; whereas, in some cases, fitness-based and naturalness-based approaches might favour the breeding of animals that experience more pain and less pleasure.

Appetite and reward

The tendency to engage in or maintain feeding behaviour is potently influenced by the rewarding properties of food. Affective and goal-directed behavioural responses for food have been assessed in response to various physiological, pharmacological and genetic manipulations to provide much insight into the neural mechanisms regulating motivation for food. In addition, several lines of evidence tie the actions of metabolic signals, neuropeptides and neurotransmitters to the modulation of the reward-relevant circuitry including midbrain dopamine neurons and corticolimbic nuclei that encode emotional and cognitive aspects of feeding. Along these lines, this review pulls together research describing the peripheral and central signalling molecules that modulate the rewarding effects of food and the underlying neural pathways.