The contribution of basal forebrain to limbic-motor integration and the mediation of motivation to action

Ventral subiculum promotes wakefulness through several pathways in male mice

The ventral subiculum (vSUB), the major output structure of the hippocampal formation, regulates motivation, stress integration, and anxiety-like behaviors that rely on heightened arousal. However, the roles and underlying neural circuits of the vSUB in wakefulness are poorly known. Using in vivo fiber photometry and multichannel electrophysiological recordings in mice, we found that the vSUB glutamatergic neurons exhibited high activities during wakefulness. Moreover, activation of vSUB glutamatergic neurons caused an increase in wakefulness and anxiety-like behaviors and induced a rapid transition from sleep to wakefulness. In addition, optogenetic stimulation of vSUB glutamatergic terminals and retrograde-targeted chemogenetic activation of vSUB glutamatergic neurons revealed that vSUB promoted arousal by innervating the lateral hypothalamus (LH), nucleus accumbens (NAc) shell, and prefrontal cortex (PFC). Nevertheless, local microinjection of dopamine D1 or D2/D3 receptor antagonist blocked the wake-promoting effect induced by chemogenetic activation of vSUB pathways. Finally, chemogenetic inhibition of vSUB glutamatergic neurons decreased arousal. Altogether, our findings reveal a prominent contribution of vSUB glutamatergic neurons to the control of wakefulness through several pathways.

Connectivity of the olfactory tubercle: inputs, outputs, and their plasticity

The olfactory tubercle (OT) is a unique part of the olfactory cortex of the mammal brain in that it is also a component of the ventral striatum. It is crucially involved in motivational behaviors, particularly in adaptive olfactory learning. This review introduces the basic properties of the OT, its synaptic connectivity with other brain areas, and the plasticity of the connectivity associated with learning behavior. The adaptive properties of olfactory behavior are discussed further based on the characteristics of OT neuronal circuits.

Oxytocinergic modulation of speech production-a double-blind placebo-controlled fMRI study

Many socio-affective behaviors, such as speech, are modulated by oxytocin. While oxytocin modulates speech perception, it is not known whether it also affects speech production. Here, we investigated effects of oxytocin administration and interactions with the functional rs53576 oxytocin receptor (OXTR) polymorphism on produced speech and its underlying brain activity. During functional magnetic resonance imaging, 52 healthy male participants read sentences out loud with either neutral or happy intonation, a covert reading condition served as a common baseline. Participants were studied once under the influence of intranasal oxytocin and in another session under placebo. Oxytocin administration increased the second formant of produced vowels. This acoustic feature has previously been associated with speech valence; however, the acoustic differences were not perceptually distinguishable in our experimental setting. When preparing to speak, oxytocin enhanced brain activity in sensorimotor cortices and regions of both dorsal and right ventral speech processing streams, as well as subcortical and cortical limbic and executive control regions. In some of these regions, the rs53576 OXTR polymorphism modulated oxytocin administration-related brain activity. Oxytocin also gated cortical-basal ganglia circuits involved in the generation of happy prosody. Our findings suggest that several neural processes underlying speech production are modulated by oxytocin, including control of not only affective intonation but also sensorimotor aspects during emotionally neutral speech.

Reward prediction error in the ERP following unconditioned aversive stimuli

Reinforcement learning in humans and other animals is driven by reward prediction errors: deviations between the amount of reward or punishment initially expected and that which is obtained. Temporal difference methods of reinforcement learning generate this reward prediction error at the earliest time at which a revision in reward or punishment likelihood is signalled, for example by a conditioned stimulus. Midbrain dopamine neurons, believed to compute reward prediction errors, generate this signal in response to both conditioned and unconditioned stimuli, as predicted by temporal difference learning. Electroencephalographic recordings of human participants have suggested that a component named the feedback-related negativity (FRN) is generated when this signal is carried to the cortex. If this is so, the FRN should be expected to respond equivalently to conditioned and unconditioned stimuli. However, very few studies have attempted to measure the FRN's response to unconditioned stimuli. The present study attempted to elicit the FRN in response to a primary aversive stimulus (electric shock) using a design that varied reward prediction error while holding physical intensity constant. The FRN was strongly elicited, but earlier and more transiently than typically seen, suggesting that it may incorporate other processes than the midbrain dopamine system.

Physiology of Energy Intake in the Weight-Reduced State

Physiological adaptations to intentional weight loss can facilitate weight regain. This review summarizes emerging findings on hypothalamic and brainstem circuitry in the regulation of body weight and identifies promising areas for research to improve therapeutic interventions for sustainable weight loss. There is good evidence that body weight is actively regulated in a homeostatic fashion similar to other physiological parameters. However, the defended level of body weight is not fixed but rather depends on environmental conditions and genetic background in an allostatic fashion. In an environment with plenty of easily available energy-dense food and low levels of physical activity, prone individuals develop obesity. In a majority of individuals with obesity, body weight is strongly defended through counterregulatory mechanisms, such as hunger and hypometabolism, making weight loss challenging. Among the options for treatment or prevention of obesity, those directly changing the defended body weight would appear to be the most effective ones. There is strong evidence that the mediobasal hypothalamus is a master sensor of the metabolic state and an integrator of effector actions responsible for the defense of adequate body weight. However, other brain areas, such as the brainstem and limbic system, are also increasingly implicated in body weight defense mechanisms and may thus be additional targets for successful therapies.

Neural circuits of social behaviors: Innate yet flexible

Social behaviors, such as mating, fighting, and parenting, are fundamental for survival of any vertebrate species. All members of a species express social behaviors in a stereotypical and species-specific way without training because of developmentally hardwired neural circuits dedicated to these behaviors. Despite being innate, social behaviors are flexible. The readiness to interact with a social target or engage in specific social acts can vary widely based on reproductive state, social experience, and many other internal and external factors. Such high flexibility gives vertebrates the ability to release the relevant behavior at the right moment and toward the right target. This maximizes reproductive success while minimizing the cost and risk associated with behavioral expression. Decades of research have revealed the basic neural circuits underlying each innate social behavior. The neural mechanisms that support behavioral plasticity have also started to emerge. Here we provide an overview of these social behaviors and their underlying neural circuits and then discuss in detail recent findings regarding the neural processes that support the flexibility of innate social behaviors.

Projections from D2 Neurons in Different Subregions of Nucleus Accumbens Shell to Ventral Pallidum Play Distinct Roles in Reward and Aversion

The nucleus accumbens shell (NAcSh) plays an important role in reward and aversion. Traditionally, NAc dopamine receptor 2-expressing (D2) neurons are assumed to function in aversion. However, this has been challenged by recent reports which attribute positive motivational roles to D2 neurons. Using optogenetics and multiple behavioral tasks, we found that activation of D2 neurons in the dorsomedial NAcSh drives preference and increases the motivation for rewards, whereas activation of ventral NAcSh D2 neurons induces aversion. Stimulation of D2 neurons in the ventromedial NAcSh increases movement speed and stimulation of D2 neurons in the ventrolateral NAcSh decreases movement speed. Combining retrograde tracing and in situ hybridization, we demonstrated that glutamatergic and GABAergic neurons in the ventral pallidum receive inputs differentially from the dorsomedial and ventral NAcSh. All together, these findings shed light on the controversy regarding the function of NAcSh D2 neurons, and provide new insights into understanding the heterogeneity of the NAcSh.

Neural Networks With Motivation

Animals rely on internal motivational states to make decisions. The role of motivational salience in decision making is in early stages of mathematical understanding. Here, we propose a reinforcement learning framework that relies on neural networks to learn optimal ongoing behavior for dynamically changing motivation values. First, we show that neural networks implementing Q-learning with motivational salience can navigate in environment with dynamic rewards without adjustments in synaptic strengths when the needs of an agent shift. In this setting, our networks may display elements of addictive behaviors. Second, we use a similar framework in hierarchical manager-agent system to implement a reinforcement learning algorithm with motivation that both infers motivational states and behaves. Finally, we show that, when trained in the Pavlovian conditioning setting, the responses of the neurons in our model resemble previously published neuronal recordings in the ventral pallidum, a basal ganglia structure involved in motivated behaviors. We conclude that motivation allows Q-learning networks to quickly adapt their behavior to conditions when expected reward is modulated by agent's dynamic needs. Our approach addresses the algorithmic rationale of motivation and makes a step toward better interpretability of behavioral data via inference of motivational dynamics in the brain.

Salience processing by glutamatergic neurons in the ventral pallidum

Organisms must make sense of a constant stream of sensory inputs from both internal and external sources which compete for attention by determining which ones are salient. The ability to detect and respond appropriately to potentially salient stimuli in the environment is critical to all organisms. However, the neural circuits that process salience are not fully understood. Here, we identify a population of glutamatergic neurons in the ventral pallidum (VP) that play a unique role in salience processing. Using cell-type-specific fiber photometry, we find that VP glutamatergic neurons are robustly activated by a variety of aversion- and reward-related stimuli, as well as novel social and non-social stimuli. Inhibition of the VP glutamatergic neurons reduces the ability to detect salient stimuli in the environment, such as aversive cue, novel conspecific and novel object. Besides, VP glutamatergic neurons project to both the lateral habenula (LHb) and the ventral tegmental area (VTA). Together, our findings demonstrate that the VP glutamatergic neurons participate in salience processing and therefore provide a new perspective on treating several neuropsychiatric disorders, including dementia and psychosis.

An insular view of the social decision-making network

Social animals must detect, evaluate and respond to the emotional states of other individuals in their group. A constellation of gestures, vocalizations, and chemosignals enable animals to convey affect and arousal to others in nuanced, multisensory ways. Observers integrate social information with environmental and internal factors to select behavioral responses to others via a process call social decision-making. The Social Decision Making Network (SDMN) is a system of brain structures and neurochemicals that are conserved across species (mammals, reptiles, amphibians, birds) that are the proximal mediators of most social behaviors. However, how sensory information reaches the SDMN to shape behavioral responses during a social encounter is not well known. Here we review the empirical data that demonstrate the necessity of sensory systems in detecting social stimuli, as well as the anatomical connectivity of sensory systems with each node of the SDMN. We conclude that the insular cortex is positioned to link integrated social sensory cues to this network to produce flexible and appropriate behavioral responses to socioemotional cues.

Shared Behavioral and Neurocircuitry Disruptions in Drug Addiction, Obesity, and Binge Eating Disorder: Focus on Group I mGluRs in the Mesolimbic Dopamine Pathway

Accumulated data from clinical and preclinical studies suggest that, in drug addiction and states of overeating, such as obesity and binge eating disorder (BED), there is an imbalance in circuits that are critical for motivation, reward saliency, executive function, and self-control. Central to these pathologies and the extensive topic of this Review are the aberrations in dopamine (DA) and glutamate (Glu) within the mesolimbic pathway. Group I metabotropic glutamate receptors (mGlus) are highly expressed in the mesolimbic pathway and are poised in key positions to modulate disruptions in synaptic plasticity and neurotransmitter release observed in drug addiction, obesity, and BED. The use of allosteric modulators of group I mGlus has been studied in drug addiction, as they offer several advantages over traditional orthosteric agents. However, they have yet to be studied in obesity or BED. With the substantial overlap between the neurocircuitry involved in drug addiction and eating disorders, group I mGlus may also provide novel targets for obesity and BED.

Gender and Hemispheric Asymmetries in Acquired Sociopathy

The emergence of enduring antisocial personality changes in previously normal individuals, or "acquired sociopathy," has consistently been reported in patients with bilateral injuries of the ventromedial prefrontal cortex. Over the past three decades, cases of acquired sociopathy with (a) bilateral or (b) unilateral sparing of the ventromedial prefrontal cortex have been reported. These cases indicate that at least in a few individuals (a') neural structures beyond the ventromedial prefrontal cortex are also critical for normal social behavior, and (b') the neural underpinnings of social cognition may be lateralized to one cerebral hemisphere. Moreover, researchers have presented evidence that lesion laterality and gender may interact in the production of acquired sociopathy. In the present review, we carried out a comprehensive literature survey seeking possible interactions between gender and hemispheric asymmetry in acquired sociopathy. We found 85 cases of acquired sociopathy due to bilateral (N = 48) and unilateral (N = 37) hemispheric injuries. A significant association between acquired sociopathy and right hemisphere damage was found in men, whereas lesions were bilateral in most women with acquired sociopathy. The present survey shows that: (i) the number of well-documented single-cases of acquired sociopathy is surprisingly small given the length of the historical record; (ii) acquired sociopathy was significantly more frequent in men after an injury of the right or of both cerebral hemispheres; and (iii) in most women who developed acquired sociopathy the injuries affected both cerebral hemispheres. These findings may be especially valuable to neuroscientists and to functional neurosurgeons in particular for the planning of tumor resections as well as for the choice of the best targets for therapeutic neuromodulation.

Cell type-specific activation of mitogen-activated protein kinase in D1 receptor-expressing neurons of the nucleus accumbens potentiates stimulus-reward learning in mice

Medium spiny neurons (MSN) in the nucleus accumbens (NAc) are a fundamental component of various aspects of motivated behavior. Although mitogen-activated protein kinase (MAPK) signaling plays a crucial role in several types of learning, the cell type-specific role of MAPK pathway in stimulus-reward learning and motivation remains unclear. We herein investigated the role of MAPK in accumbal MSNs in reward-associated learning and memory. During the acquisition of Pavlovian conditioning, the number of phosphorylated MAPK1/3-positive cells was increased significantly and exclusively in the NAc core by 7-days of extensive training. MAPK signaling in the respective D1R- and D2R-MSNs was manipulated by transfecting an adeno-associated virus (AAV) plasmid into the NAc of Drd1a-Cre and Drd2-Cre transgenic mice. Potentiation of MAPK signaling shifted the learning curve of Pavlovian conditioning to the left only in Drd1a-Cre mice, whereas such manipulation in D2R-MSNs had negligible effects. In contrast, MAPK manipulation in D2R-MSNs of the NAc core significantly increased motivation for food rewards as found in Drd1a-Cre mice. These results suggest that MAPK signaling in the D1R-MSNs of NAc core plays an important role in stimulus-reward learning, while MAPK signaling in both D1R- and D2R-MSNs is involved in motivation for natural rewards.

Amphetamine Self-Administration and Its Extinction Alter the 5-HT1B Receptor Protein Levels in Designated Structures of the Rat Brain

Manipulation of the serotonin (5-HT)_1B receptors can modify the behavioral effects of amphetamine including its reinforcing properties. Focus of this study was to examine changes in 5-HT_1B receptor protein expression in several brain structures linked to substance drug disorder in different stages of amphetamine addiction—single session of amphetamine self-administration, 20 consecutive days of amphetamine self-administration, and 3 and 14 days of extinction from chronic drug intake. “Yoked” procedure was employed to set apart pharmacological and motivational effects of amphetamine intoxication. Immunohistofluorescence was performed on brain slices containing the following regions: nucleus accumbens (NAc) shell and core, globus pallidum (GP) lateral and ventral, hippocampus (HIP), substantia nigra (SN), and ventral tegmental area (VTA). Single amphetamine session decreased the amount of 5-HT_1B receptors in SN, VTA, and HIP in active and yoked rats. On the contrary, 20 days of chronic amphetamine exposure triggered elevation of 5-HT_1B receptors exclusively in animals that voluntarily administered the drug in NAc core, GP ventral, and HIP. Furthermore, 14-day (but not 3-day) extinction from amphetamine increased the 5-HT_1B receptor expression in ventral and lateral GP, HIP, and SN. This study is the first to demonstrate that exposure to amphetamine and its extinction alter the expression of 5-HT_1B receptors in various rat brain regions, and those changes seem to be transient and region specific. Importantly, since increased expression of 5-HT_1B receptor after chronic amphetamine self-administration was limited only to active group of animals, we suggest that 5-HT_1B receptor is linked to motivational aspect of addiction.

Lateral preoptic and ventral pallidal roles in locomotion and other movements

The lateral preoptic area (LPO) and ventral pallidum (VP) are structurally and functionally distinct territories in the subcommissural basal forebrain. It was recently shown that unilateral infusion of the GABAA receptor antagonist, bicuculline, into the LPO strongly invigorates exploratory locomotion, whereas bicuculline infused unilaterally into the VP has a negligible locomotor effect, but when infused bilaterally, produces vigorous, abnormal pivoting and gnawing movements and compulsive ingestion. This study was done to further characterize these responses. We observed that bilateral LPO infusions of bicuculline activate exploratory locomotion only slightly more potently than unilateral infusions and that unilateral and bilateral LPO injections of the GABAA receptor agonist muscimol potently suppress basal locomotion, but only modestly inhibit locomotion invigorated by amphetamine. In contrast, unilateral infusions of muscimol into the VP affect basal and amphetamine-elicited locomotion negligibly, but bilateral VP muscimol infusions profoundly suppress both. Locomotor activation elicited from the LPO by bicuculline was inhibited modestly and profoundly by blockade of dopamine D2 and D1 receptors, respectively, but was not entirely abolished even under combined blockade of dopamine D1 and D2 receptors. That is, infusing the LPO with bic caused instances of near normal, even if sporadic, invigoration of locomotion in the presence of saturating dopamine receptor blockade, indicating that LPO can stimulate locomotion in the absence of dopamine signaling. Pivoting following bilateral VP bicuculline infusions was unaffected by dopamine D2 receptor blockade, but was completely suppressed by D1 receptor blockade. The present results are discussed in a context of neuroanatomical and functional organization underlying exploratory locomotion and adaptive movements.

Pro-dopamine regulator, KB220Z, attenuates hoarding and shopping behavior in a female, diagnosed with SUD and ADHD

Background Addictive-like behaviors (e.g., hoarding and shopping) may be the result of the cumulative effects of dopaminergic and other neurotransmitter genetic variants as well as elevated stress levels. We, therefore, propose that dopamine homeostasis may be the preferred goal in combating such challenging and unwanted behaviors, when simple dopaminergic activation through potent agonists may not provide any resolution. Case presentation C.J. is a 38-year-old, single, female, living with her mother. She has a history of substance use disorder as well as attention deficit hyperactivity disorder, inattentive type. She had been stable on buprenorphine/naloxone combination and amphetamine, dextroamphetamine mixed salts for many years when unexpectedly she lost her job for oversleeping and not calling into work. KB200z (a pro-dopamine compound) was added to her regimen for complaints of low drive and motivation. After taking this nutraceutical for 4 weeks, she noticed a marked improvement in her mental status and many behaviors. She noted that her shopping and hoarding addictions had appreciably decreased. Furthermore, her lifelong history of terrifying lucid dreams was eliminated. Finally, she felt more in control; her locus of control shifted from external to more internal. Discussion The hypothesis is that C.J.'s reported, behavioral, and psychological benefits resulted from the pro-dopamine-regulating effect of KB220Z across the brain reward system. Conclusions This effect, we surmise, could be the result of a new dopamine balance, across C.J.'s brain reward system. Dopamine homeostasis is an effect of KB220Z seen in both animal and human placebo-controlled fMRI experiments.

Effects of nucleus accumbens oxytocin and its antagonist on social approach behavior

Severe impairment of social interaction is a core symptom of numerous psychiatric disorders. Oxytocin (OT) has been shown to be involved in various aspects of social behavior related to reproduction, but little is known about its effects on nonreproductive social interaction between adults or the neuroanatomical location where OT exerts its action. Here, we examined the nucleus accumbens, a region of the brain containing high levels of the oxytocin receptor (OTR) and comprising an important node in the neural circuitry possibly related to social interaction. Behavioral effects of a local microinfusion of OT (0.1, 1, and 10 ng/side) and an oxytocin receptor antagonist (OTR-A) (1, 10, and 100 ng/side) were evaluated in naturally high social and low social female and male monogamous mandarin voles (Microtus mandarinus) using the social preference paradigm and open-field tests. The results showed that administration of 1 ng/side OT increased social preference; however, this effect was not apparent at lower or higher doses. OT did not alter anxiety-like behavior or total locomotion. Microinfusions of a selective OTR-A at 10 and 100 ng doses reduced social approach behavior; a dose of 1 ng had no effect. In conclusion, our results suggest that accumbal OT and OTR-A regulate social preferences in voles in a dose-dependent manner.

Role of perineuronal nets in the anterior dorsal lateral hypothalamic area in the acquisition of cocaine-induced conditioned place preference and self-administration

Addiction involves drug-induced neuroplasticity in the circuitry of motivated behavior, which includes the medial forebrain bundle and the lateral hypothalamic area. Emerging at the forefront of neuroplasticity regulation are specialized extracellular matrix (ECM) structures that form perineuronal nets (PNNs) around certain neurons, mainly parvalbumin positive (PV+), fast-spiking interneurons (FSINs), making them a promising target for the regulation of drug-induced neuroplasticity. Despite the emerging significance of PNNs in drug-induced neuroplasticity and the well-established role of the lateral hypothalamic area (LHA) in reward, reinforcement, and motivation, very little is known about how PNN-expressing neurons control drug-seeking behavior. We found that a discrete region of the anterior dorsal LHA (LHAad) exhibited robust PNN and dense ECM expression. Approximately 87% of parvalbumin positive (PV+) neurons co-expressed the PNN marker Wisteria floribunda agglutinin (WFA), while 62% of WFA positive (WFA+) neurons co-expressed PV in the LHAad of drug naïve rats. Removal of PNNs within this brain region via chrondroitinase ABC (Ch-ABC) administration abolished acquisition of cocaine-induced CPP and significantly attenuated the acquisition of cocaine self-administration (SA). Removal of LHAad PNNs did not affect locomotor activity, sucrose intake, sucrose-induced CPP, or acquisition of sucrose SA in separate groups of cocaine naïve animals. These data suggest that PNN-dependent neuroplasticity within the LHAad is critical for the acquisition of both cocaine-induced CPP and SA but is not general to all rewards, and that PNN degradation may have utility for the management of drug-associated behavioral plasticity and memory in cocaine addicts.

Grey matter abnormalities in children and adolescents with functional neurological symptom disorder

Objective

Functional neurological symptom disorder refers to the presence of neurological symptoms not explained by neurological disease. Although this disorder is presumed to reflect abnormal function of the brain, recent studies in adults show neuroanatomical abnormalities in brain structure. These structural brain abnormalities have been presumed to reflect long-term adaptations to the disorder, and it is unknown whether child and adolescent patients, with illness that is typically of shorter duration, show similar deficits or have normal brain structure.

Method

High-resolution, three-dimensional T1-weighted magnetic resonance images (MRIs) were acquired in 25 patients (aged 10–18 years) and 24 healthy controls. Structure was quantified in terms of grey matter volume using voxel-based morphometry. Post hoc, we examined whether regions of structural difference related to a measure of motor readiness to emotional signals and to clinical measures of illness duration, illness severity, and anxiety/depression.

Results

Patients showed greater volumes in the left supplementary motor area (SMA) and right superior temporal gyrus (STG) and dorsomedial prefrontal cortex (DMPFC) (corrected p < 0.05). Previous studies of adult patients have also reported alterations of the SMA. Greater SMA volumes correlated with faster reaction times in identifying emotions but not with clinical measures.

Conclusions

The SMA, STG, and DMPFC are known to be involved in the perception of emotion and the modulation of motor responses. These larger volumes may reflect the early expression of an experience-dependent plasticity process associated with increased vigilance to others' emotional states and enhanced motor readiness to organize self-protectively in the context of the long-standing relational stress that is characteristic of this disorder.

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We used high-resolution MRI to investigate brain structure in children presenting with acute functional neurological symptom disorder (FND).

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Patients had multiple antecedent stressors, a long-standing history of relational stress and at-risk attachment strategies.

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Patients had greater volumes in the SMA—where motor-, cognitive-, and emotion-processing signals interact to influence motor function.

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FND may involve experience-dependent changes in brain structure alongside experience-dependent changes in brain function.

The role of the human globus pallidus in Huntington's disease

Huntington's disease (HD) is characterized by pronounced pathology of the basal ganglia, with numerous studies documenting the pattern of striatal neurodegeneration in the human brain. However, a principle target of striatal outflow, the globus pallidus (GP), has received limited attention in comparison, despite being a core component of the basal ganglia. The external segment (GPe) is a major output of the dorsal striatum, connecting widely to other basal ganglia nuclei via the indirect motor pathway. The internal segment (GPi) is a final output station of both the direct and indirect motor pathways of the basal ganglia. The ventral pallidum (VP), in contrast, is a primary output of the limbic ventral striatum. Currently, there is a lack of consensus in the literature regarding the extent of GPe and GPi neurodegeneration in HD, with a conflict between pallidal neurons being preserved, and pallidal neurons being lost. In addition, no current evidence considers the fate of the VP in HD, despite it being a key structure involved in reward and motivation. Understanding the involvement of these structures in HD will help to determine their involvement in basal ganglia pathway dysfunction in the disease. A clear understanding of the impact of striatal projection loss on the main neurons that receive striatal input, the pallidal neurons, will aid in the understanding of disease pathogenesis. In addition, a clearer picture of pallidal involvement in HD may contribute to providing a morphological basis to the considerable variability in the types of motor, behavioral, and cognitive symptoms in HD. This review aims to highlight the importance of the globus pallidus, a critical component of the cortical-basal ganglia circuits, and its role in the pathogenesis of HD. This review also summarizes the current literature relating to human studies of the globus pallidus in HD.

Pilot clinical observations between food and drug seeking derived from fifty cases attending an eating disorder clinic

Background The reward deficiency syndrome hypothesis posits that genes are responsible for reward dependence and related behaviors. There is evidence that both bulimia and anorexia nervosa, especially in women, have been linked to a lifetime history of substance use disorder (SUD). There are difficulties in accepting food as an addiction similar to drugs; however, increasingly neuroimaging studies favor such an assertion. Case presentations We are reporting the evidence of comorbidity of eating disorders with SUD found within these case presentations. We show 50 case reports derived from two independent treatment centers in Florida that suggest the commonality between food and drug addictions. In an attempt to provide data from this cohort, many participants did not adequately respond to our questionnaire. Discussion We propose that dopamine agonist therapy may be of common benefit. Failure in the past may reside in too powerful D2 agonist activity leading to D2 receptor downregulation, while the new methodology may cause a reduction of "dopamine resistance" by inducing "dopamine homeostasis." While this is not a definitive study, it does provide some additional clinical evidence that these two addictions are not mutually exclusive. Conclusion Certainly, it is our position that there is an overlap between food- and drug-seeking behavior. We propose that the studies focused on an effort to produce natural activation of dopaminergic reward circuitry as a type of common therapy may certainly be reasonable. Additional research is warranted.

Neural Activity in the Ventral Pallidum Encodes Variation in the Incentive Value of a Reward Cue

There is considerable individual variation in the extent to which reward cues are attributed with incentive salience. For example, a food-predictive conditioned stimulus (CS; an illuminated lever) becomes attractive, eliciting approach toward it only in some rats ("sign trackers," STs), whereas others ("goal trackers," GTs) approach the food cup during the CS period. The purpose of this study was to determine how individual differences in Pavlovian approach responses are represented in neural firing patterns in the major output structure of the mesolimbic system, the ventral pallidum (VP). Single-unit in vivo electrophysiology was used to record neural activity in the caudal VP during the performance of ST and GT conditioned responses. All rats showed neural responses to both cue onset and reward delivery but, during the CS period, STs showed greater neural activity than GTs both in terms of the percentage of responsive neurons and the magnitude of the change in neural activity. Furthermore, neural activity was positively correlated with the degree of attraction to the cue. Given that the CS had equal predictive value in STs and GTs, we conclude that neural activity in the VP largely reflects the degree to which the CS was attributed with incentive salience.

SIGNIFICANCE STATEMENT

Cues associated with reward can acquire motivational properties (i.e., incentive salience) that cause them to have a powerful influence on desire and motivated behavior. There are individual differences in sensitivity to reward-paired cues, with some individuals attaching greater motivational value to cues than others. Here, we investigated the neural activity associated with these individual differences in incentive salience. We found that cue-evoked neural firing in the ventral pallidum (VP) reflected the strength of incentive motivation, with the greatest neural responses occurring in individuals that demonstrated the strongest attraction to the cue. This suggests that the VP plays an important role in the process by which cues gain control over motivation and behavior.

Manipulating the Placebo Response in Experimental Pain by Altering Doctor's Performance Style

Background: Performance is paramount in traditional healing rituals. From a Western perspective, such performative behavior can be understood principally as inducing patients’ faith in the performer’s supernatural healing powers and effecting positive changes through the same mechanisms attributed to the placebo response, which is defined as improvement of clinical outcome in individuals receiving inactive treatment. Here we examined the possibility of using theatrical performance tools, including stage directions and scripting, to reproducibly manipulate the style and content of a simulated doctor–patient encounter and influence the placebo response in experimental pain.

Methods: A total of 122 healthy volunteers (18–45 years, 76 men) exposed to experimental pain (the cold pressor test) were assessed for pain threshold and tolerance before and after receiving a placebo cream from a “doctor” impersonated by a trained actor. The actor alternated between two distinct scripts and stage directions, i.e., performance styles created by a theater director/playwright, one emulating a standard doctor–patient encounter (scenario A) and the other emphasizing attentiveness and strong suggestion, elements also present in ritual healing (scenario B). The placebo response size was calculated as the %difference in pain threshold and tolerance after exposure relative to baseline. In addition, subjects demonstrating a ≥30% increase in pain threshold or tolerance relative to baseline were defined as responders. Each encounter was videotaped in its entirety.

Results: Inspection of the videotapes confirmed the reproducibility and consistency of the distinct scenarios enacted by the “doctor”-performer. Furthermore, scenario B resulted in a significant increase in pain threshold relative to scenario A. Interestingly, this increase derived from the placebo responder subgroup; as shown by two-way analysis of variance (performance style, F = 4.30; p = 0.040; η² = 0.035; style × responder status interaction term, F = 5.21; p = 0.024) followed by post hoc analysis showing a ∼60% increase in pain threshold in responders exposed to scenario B (p = 0.020).

Conclusion: These results support the hypothesis that structured manipulation of physician’s verbal and non-verbal performance, designed to build rapport and increase faith in treatment, is feasible and may have a significant beneficial effect on the size of the response to placebo analgesia. They also demonstrate that subjects, who are not susceptible to placebo, are also not susceptible to performance style.

Ventral Pallidum Neurons Encode Incentive Value and Promote Cue-Elicited Instrumental Actions

The ventral pallidum (VP) is posited to contribute to reward seeking by conveying upstream signals from the nucleus accumbens (NAc). Yet, very little is known about how VP neuron responses contribute to behavioral responses to incentive cues. Here, we recorded activity of VP neurons in a cue-driven reward-seeking task previously shown to require neural activity in the NAc. We find that VP neurons encode both learned cue value and subsequent reward seeking and that activity in VP neurons is required for robust cue-elicited reward seeking. Surprisingly, the onset of VP neuron responses occurs at a shorter latency than cue-elicited responses in NAc neurons. This suggests that this VP encoding is not a passive response to signals generated in the NAc and that VP neurons integrate sensory and motivation-related information received directly from other mesocorticolimbic inputs.

Ventral pallidal coding of a learned taste aversion

The hedonic value of a sweet food reward, or how much a taste is 'liked', has been suggested to be encoded by neuronal firing in the posterior ventral pallidum (VP). Hedonic impact can be altered by psychological manipulations, such as taste aversion conditioning, which can make an initially pleasant sweet taste become perceived as disgusting. Pairing nausea-inducing LiCl injection as a Pavlovian unconditioned stimulus (UCS) with a novel taste that is normally palatable as the predictive conditioned stimulus (CS+) suffices to induce a learned taste aversion that changes orofacial 'liking' responses to that sweet taste (e.g., lateral tongue protrusions) to 'disgust' reactions (e.g., gapes) in rats. We used two different sweet tastes of similar initial palatability (a sucrose solution and a polycose/saccharin solution, CS ± assignment was counterbalanced across groups) to produce a discriminative conditioned aversion. Only one of those tastes (arbitrarily assigned and designated as CS+) was associatively paired with LiCl injections as UCS to form a conditioned aversion. The other taste (CS-) was paired with mere vehicle injections to remain relatively palatable as a control sweet taste. We recorded the neural activity in VP in response to each taste, before and after aversion training. We found that the safe and positively hedonic taste always elicited excitatory increases in firing rate of VP neurons. By contrast, aversion learning reversed the VP response to the 'disgusting' CS+ taste from initial excitation into a conditioned decrease in neuronal firing rate after training. Such neuronal coding of hedonic impact by VP circuitry may contribute both to normal pleasure and disgust, and disruptions of VP coding could result in affective disorders, addictions and eating disorders.

Sources of input to the rostromedial tegmental nucleus, ventral tegmental area, and lateral habenula compared: A study in rat

Profound inhibitory control exerted on midbrain dopaminergic neurons by the lateral habenula (LHb), which has mainly excitatory outputs, is mediated by the GABAergic rostromedial tegmental nucleus (RMTg), which strongly innervates dopaminergic neurons in the ventral midbrain. Early reports indicated that the afferent connections of the RMTg, excepting its very strong LHb inputs, do not differ appreciably from those of the ventral tegmental area (VTA). Presumably, however, the RMTg contributes more to behavioral synthesis than to simply invert the valence of the excitatory signal coming from the LHb. Therefore, the present study was done to directly compare the inputs to the RMTg and VTA and, in deference to its substantial involvement with this circuitry, the LHb was also included in the comparison. Data indicated that, while the afferents of the RMTg, VTA, and LHb do originate within the same large pool of central nervous system (CNS) structures, each is also related to structures that project more strongly to it than to the others. The VTA gets robust input from ventral striatopallidum and extended amygdala, whereas RMTg biased inputs arise in structures with a more direct impact on motor function, such as deep layers of the contralateral superior colliculus, deep cerebellar and several brainstem nuclei, and, via a relay in the LHb, the entopeduncular nucleus. Input from the ventral pallidal-lateral preoptic-lateral hypothalamus continuum is strong in the RMTg and VTA and dominant in the LHb. Axon collateralization was also investigated, providing additional insights into the organization of the circuitry of this important triad of structures.

Anxiolytic effect of neurotensin microinjection into the ventral pallidum

Neurotensin (NT) acts as a neurotransmitter and neuromodulator in the central nervous system. NT is involved in reward and memory processes, drug addiction and also in the regulation of anxiety. The ventral pallidum (VP) receives neurotensinergic innervation from the ventral striatopallidal pathway originating from the nucleus accumbens. Positive reinforcing effects of NT in the VP had been shown recently, however the possible effects of NT on anxiety have not been examined yet. In our present experiments, the effects of NT on anxiety were investigated in the VP. In male Wistar rats bilateral microinjections of 100 ng or 250 ng NT were delivered in the volume of 0.4 μl into the VP, and elevated plus maze (EPM) test was performed. In another groups of animals, 35 ng NT-receptor 1 (NTR1) antagonist SR 48,692 was applied by itself, or microinjected 15 min before 100 ng NT treatment. Open field test (OPF) was also conducted. The 100 ng dose of NT had anxiolytic effect, but the 250 ng NT did not influence anxiety. The antagonist pretreatment inhibited the effect of NT, while the antagonist itself had no effect. In the OPF test there was no difference among the groups. Our present results show that microinjection of NT into the VP induces anxiolytic effect, which is specific to the NTR1 receptors because it can be eliminated by a specific NTR1 antagonist. It is also substantiated that neither the NT, nor the NTR1 antagonist in the VP influences locomotor activity.

Histamine is required for H₃ receptor-mediated alcohol reward inhibition, but not for alcohol consumption or stimulation

BACKGROUND AND PURPOSE

Conflicting data have been published on whether histamine is inhibitory to the rewarding effects of abused drugs. The purpose of this study was to clarify the role of neuronal histamine and, in particular, H₃ receptors in alcohol dependence-related behaviours, which represent the addictive effects of alcohol.

EXPERIMENTAL APPROACH

Alcohol-induced conditioned place preference (alcohol-CPP) was used to measure alcohol reward. Alcohol-induced locomotor stimulation, alcohol consumption and kinetics were also assessed. mRNA levels were quantified using radioactive in situ hybridization.

KEY RESULTS

Low doses of H₃ receptor antagonists, JNJ-10181457 and JNJ-39220675, inhibited alcohol reward in wild-type (WT) mice. However, these H₃ receptor antagonists did not inhibit alcohol reward in histidine decarboxylase knock-out (HDC KO) mice and a lack of histamine did not alter alcohol consumption. Thus H₃ receptor antagonists inhibited alcohol reward in a histamine-dependent manner. Furthermore, WT and HDC KO mice were similarly stimulated by alcohol. The expression levels of dopamine D₁ and D₂ receptors, STEP61 and DARPP-32 mRNA in striatal subregions were unaltered in HDC KO mice. No differences were seen in alcohol kinetics in HDC KO compared to WT control animals. In addition, JNJ-39220675 had no effect on alcohol kinetics in WT mice.

CONCLUSIONS AND IMPLICATIONS

These data suggest that histamine is required for the H₃ receptor-mediated inhibition of alcohol-CPP and support the hypothesis that the brain histaminergic system has an inhibitory role in alcohol reward. Increasing neuronal histamine release via H₃ receptor blockade could therefore be a novel way of treating alcohol dependence.

Facilitation of short-term memory by histaminergic neurons in the nucleus accumbens is independent of cholinergic and glutamatergic transmission

BACKGROUND AND PURPOSE

Here, we have investigated whether learning and/or short-term memory was associated with release of ACh and glutamate in the rat nucleus accumbens (NAc). Additionally, neurotransmitter release in the NAc was assessed during facilitation of cognitive processes by antagonists of inhibitory histamine autoreceptors.

EXPERIMENTAL APPROACH

The olfactory, social memory test was used in combination with push-pull superfusion of the NAc. A male, juvenile rat was exposed twice to an adult male rat at intervals of 60 or 90 min, and release of ACh and glutamate was determined in the NAc of the conscious adult rat. Histamine receptor antagonists were applied i.c.v.

KEY RESULTS

First exposure of a juvenile rat to an adult rat increased ACh and glutamate release in the NAc of the adult rat. Repetition of exposure after 60 min did not change release of ACh and glutamate, while contact time to recognition (CTR) was shortened. Repetition of exposure after an interval of 90 min prolonged CTR and enhanced accumbal ACh and glutamate release rates. Injection (i.c.v.) of thioperamide (histamine H3 receptor antagonist) together with famotidine (H₂ receptor antagonist), 80 min prior to second exposure, diminished CTR and abolished ACh and glutamate release when second exposure was carried out 90 min after the first one.

CONCLUSIONS AND IMPLICATIONS

Histaminergic neurons per se facilitated short-term memory, without activation of cholinergic and/or glutamatergic neurons in the NAc of rats. Cholinergic and glutamatergic neurons within the NAc contributed to learning but not to recall of memory.

Bidirectional modulation of incubation of cocaine craving by silent synapse-based remodeling of prefrontal cortex to accumbens projections

Glutamatergic projections from the medial prefrontal cortex (mPFC) to nucleus accumbens (NAc) contribute to cocaine relapse. Here we show that silent synapse-based remodeling of the two major mPFC-to-NAc projections differentially regulated the progressive increase in cue-induced cocaine seeking after withdrawal (incubation of cocaine craving). Specifically, cocaine self-administration in rats generated AMPA receptor-silent glutamatergic synapses within both infralimbic (IL) and prelimbic mPFC (PrL) to NAc projections, measured after 1 day of withdrawal. After 45 days of withdrawal, IL-to-NAc silent synapses became unsilenced/matured by recruiting calcium-permeable (CP) AMPARs, whereas PrL-to-NAc silent synapses matured by recruiting non-CP-AMPARs, resulting in differential remodeling of these projections. Optogenetic reversal of silent synapse-based remodeling of IL-to-NAc and PrL-to-NAc projections potentiated and inhibited, respectively, incubation of cocaine craving on withdrawal day 45. Thus, pro- and antirelapse circuitry remodeling is induced in parallel after cocaine self-administration. These results may provide substrates for utilizing endogenous antirelapse mechanisms to reduce cocaine relapse.

Emotion and relative reward processing: an investigation on instrumental successive negative contrast and ultrasonic vocalizations in the rat

Incentive contrast effects include changes in behavioral responses after a reward upshift (positive contrast) or downshift (negative contrast). Proposed influences on these behavioral changes are emotional state reactions after experiencing or anticipating a change in reward outcome. Rat ultrasonic vocalizations have been shown to be indicators of emotional state during behavior and anticipatory periods. The objective of the present study was to monitor rodent ultrasounds during incentive contrast using a classical runway procedure called instrumental successive negative contrast. The procedure is one that has been used often to examine incentive relativity because of its reliability in measuring negative contrast effects. Rats were trained to run in the alleyway to receive a high (12 pellets) or low magnitude (1 pellet) outcome. The high magnitude was then shifted to the low and running speeds in the alleyway for the reward and USV emission were compared. Replicating previous work, a negative contrast effect was observed with postshift running speeds significantly slower in the shifted group compared to the unshifted group. USVs did not follow the same pattern with an apparent lack of significant differences between the groups following the reward downshift. We also tested another group of animals using a visual predictive cue in the same runway test. When visual cues predicted high or low magnitude outcome, no incentive contrast was found for the running speeds following an outcome downshift, but a weak contrast effect was observed for the USV emission. These results demonstrate a separation between USVs and behavioral indicators of incentive contrast suggesting that concomitant shifts in negative affect may not be necessary for anticipatory relative reward processes.

Deep brain stimulation for treatment-refractory obsessive compulsive disorder: a systematic review

BACKGROUND

Obsessive-compulsive disorder is one of the most disabling of all psychiatric illnesses. Despite available pharmacological and psychotherapeutic treatments about 10% of patients remain severely affected and are considered treatment-refractory. For some of these patients deep brain stimulation offers an appropriate treatment method. The scope of this article is to review the published data and to compare different target structures and their effectiveness.

METHODS

PubMed search, last update June 2013, was conducted using the terms "deep brain stimulation" and "obsessive compulsive disorder".

RESULTS

In total 25 studies were found that reported five deep brain stimulation target structures to treat obsessive-compulsive disorder: the anterior limb of the internal capsule (five studies including 14 patients), nucleus accumbens (eight studies including 37 patients), ventral capsule/ventral striatum (four studies including 29 patients), subthalamic nucleus (five studies including 23 patients) and inferior thalamic peduncle (two studies including 6 patients). Despite the anatomical diversity, deep brain stimulation treatment results in similar response rates for the first four target structures. Inferior thalamic peduncle deep brain stimulation results in higher response rates but these results have to be interpreted with caution due to a very small number of cases. Procedure and device related adverse events are relatively low, as well as stimulation or therapy related side effects. Most stimulation related side effects are transient and decline after stimulation parameters have been changed.

CONCLUSION

Deep brain stimulation in treatment-refractory obsessive-compulsive disorder seems to be a relatively safe and promising treatment option. However, based on these studies no superior target structure could be identified. More research is needed to better understand mechanisms of action and response predictors that may help to develop a more personalized approach for these severely affected obsessive compulsive patients.

Digital holographic microscopy discriminates sex differences in medial prefrontal cortex GABA neurons following amphetamine sensitization

Sex differences have been noted in patterns of drug use and relapse, and in particular with amphetamine abuse, implicating estradiol in mediating female neurobehavioral responses. To investigate the interaction of estradiol with amphetamine-induced hyperactivity, we compared male, intact female (INTACT), ovariectomized (OVX) and ovariectomized estradiol-treated (OVX+EB) female rats receiving repeated amphetamine (AMPH) treatment. All rats received intermittent AMPH injections for three days, and baseline and post-injection locomotor activity as well as fine-motor movements were recorded. Upon completion of behavioral experiments, immunohistochemistry was performed to assess parvalbumin-immunoreactive (PV-IR) GABAergic neurons in the medial prefrontal cortex (mPFC). Results indicate that AMPH induced greater behavioral response during habituation among the INTACT animals, and post-injection hyperactivity was apparent on days 2 and 3, among INTACT and OVX+EB females. For INTACT animals, the hyperactivity was most pronounced when estrogen levels were high. Immunohistochemical analysis using digital holographic microscopy revealed INTACT and OVX+EB females had less expression and smaller somatic area of PV-IR neurons in the mPFC. These data provide evidence for rapid development of sex differences in response to AMPH that correlates with sexually dimorphic alterations in a subset of mPFC GABAergic neurons implicated in modulating forebrain dopamine projections.

Reward for food odors: an fMRI study of liking and wanting as a function of metabolic state and BMI

Brain reward systems mediate liking and wanting for food reward. Here, we explore the differential involvement of the following structures for these two components: the ventral and dorsal striatopallidal area, orbitofrontal cortex (OFC), anterior insula and anterior cingulate. Twelve healthy female participants were asked to rate pleasantness (liking of food and non-food odors) and the desire to eat (wanting of odor-evoked food) during event-related functional magnetic resonance imaging (fMRI). The subjective ratings and fMRI were performed in hunger and satiety states. Activations of regions of interest were compared as a function of task (liking vs wanting), odor category (food vs non-food) and metabolic state (hunger vs satiety). We found that the nucleus accumbens and ventral pallidum were differentially involved in liking or wanting during the hunger state, which suggests a reciprocal inhibitory influence between these structures. Neural activation of OFC subregions was correlated with either liking or wanting ratings, suggesting an OFC role in reward processing magnitude. Finally, during the hunger state, participants with a high body mass index exhibited less activation in neural structures underlying food reward processing. Our results suggest that food liking and wanting are two separable psychological constructs and may be functionally segregated within the cortico-striatopallidal circuit.

The link between dopamine function and apathy in cannabis users: an [18F]-DOPA PET imaging study

RATIONALE

Cannabis is the most widely used illicit drug in the world, and regular use has been associated with reduced motivation, i.e. apathy. Regular long-term cannabis use has been associated with reduced dopamine synthesis capacity. The mesolimbic dopaminergic system mediates the processing of incentive stimuli by modifying their motivational value, which in turn is modulated by endocannabinoid signalling. Thus, it has been proposed that dopaminergic dysfunction underlies the apathy associated with chronic cannabis use.

OBJECTIVES

The aim of this study was to examine the relationship between dopaminergic function and subjective apathy in cannabis users.

METHODS

We measured dopamine synthesis capacity (indexed as the influx rate constant K i(cer)) via 3,4-dihydroxy-6-[(18)F]-fluoro-l-phenylalanine positron emission tomography and subjective apathy using the self-rated Apathy Evaluation Scale (AES-S) in 14 regular cannabis users.

RESULTS

All subjects scored in excess of 34 points on the AES-S (median [interquartile range] 59.5 [7.5]), indicative of significant apathy based on normative data. K i (cer) was inversely correlated to AES-S score in the whole striatum and its associative functional subdivision (Spearman's rho = -0.64, p = 0.015 [whole striatum]; rho = -0.69, p = 0.006 [associative]) but not in the limbic or sensorimotor striatal subdivisions. There were no significant relationships between AES-S and current cannabis consumption (rho = 0.28, p = 0.34) or age of first cannabis use (rho = 0.25, p = 0.40).

CONCLUSIONS

These findings indicate that the reduction in striatal dopamine synthesis capacity associated with chronic cannabis use may underlie reduced reward sensitivity and a motivation associated with chronic cannabis use.

Double dissociation between the contributions of the septal and temporal hippocampus to spatial learning: the role of prior experience

The mammalian hippocampus is anatomically heterogeneous along its longitudinal axis, and there is evidence that distinct functions are executed by different septotemporal subregions. The best documented example is the dependency of spatial learning on the septal, but not the temporal, hippocampus. Here, we carried out a watermaze memory task in rats with partial lesions of the septal or temporal hippocampus made either before or after training. We then studied memory retention, reversal, and new spatial learning in a novel environment. This resulted in the surprising finding that spatial learning in a new environment is dependent on the temporal hippocampus in rats with preoperative experience of a different pool. Rats with septal hippocampal lesions made after learning not only retained the focused search strategy that was acquired during preoperative training, but were also capable of rapid spatial learning in a second pool. This demonstrates that once spatial information has been acquired in one context, related new learning in a different context can be mediated by the temporal hippocampus, a result that challenges the widely held view that spatial memory is an exclusive function of the septal hippocampus.

Human hippocampal processing of environmental novelty during spatial navigation

The detection and processing of novel information encountered as we explore our environment is crucial for learning and adaptive behavior. The human hippocampus has been strongly implicated in laboratory tests of novelty detection and episodic memory, but has been less well studied during more ethological tasks such as spatial navigation, typically used in animals. We examined fMRI BOLD activity as a function of environmental and object novelty as humans performed an object-location virtual navigation task. We found greater BOLD response to novel relative to familiar environments in the hippocampus and adjacent parahippocampal gyrus. Object novelty was associated with increased activity in the posterior parahippocampal/fusiform gyrus and anterior hippocampus extending into the amygdala and superior temporal sulcus. Importantly, whilst mid-posterior hippocampus was more sensitive to environmental novelty than object novelty, the anterior hippocampus responded similarly to both forms of novelty. Amygdala activity showed an increase for novel objects that decreased linearly over the learning phase. By investigating how participants learn and use different forms of information during spatial navigation, we found that medial temporal lobe (MTL) activity reflects both the novelty of the environment and of the objects located within it. This novelty processing is likely supported by distinct, but partially overlapping, sets of regions within the MTL.

Cocaine dysregulates opioid gating of GABA neurotransmission in the ventral pallidum

The ventral pallidum (VP) is a target of dense nucleus accumbens projections. Many of these projections coexpress GABA and the neuropeptide enkephalin, a δ and μ opioid receptor (MOR) ligand. Of these two, the MOR in the VP is known to be involved in reward-related behaviors, such as hedonic responses to palatable food, alcohol intake, and reinstatement of cocaine seeking. Stimulating MORs in the VP decreases extracellular GABA, indicating that the effects of MORs in the VP on cocaine seeking are via modulating GABA neurotransmission. Here, we use whole-cell patch-clamp on a rat model of withdrawal from cocaine self-administration to test the hypothesis that MORs presynaptically regulate GABA transmission in the VP and that cocaine withdrawal changes the interaction between MORs and GABA. We found that in cocaine-extinguished rats pharmacological activation of MORs no longer presynaptically inhibited GABA release, whereas blocking the MORs disinhibited GABA release. Moreover, MOR-dependent long-term depression of GABA neurotransmission in the VP was lost in cocaine-extinguished rats. Last, GABA neurotransmission was found to be tonically suppressed in cocaine-extinguished rats. These substantial synaptic changes indicated that cocaine was increasing tone on MOR receptors. Accordingly, increasing endogenous tone by blocking the enzymatic degradation of enkephalin inhibited GABA neurotransmission in yoked saline rats but not in cocaine-extinguished rats. In conclusion, our results indicate that following withdrawal from cocaine self-administration enkephalin levels in the VP are elevated and the opioid modulation of GABA neurotransmission is impaired. This may contribute to the difficulties withdrawn addicts experience when trying to resist relapse.

The Effects of Exercise Training on Anxiety

This review summarizes the extant evidence of the effects of exercise training on anxiety among healthy adults, adults with a chronic illness, and individuals diagnosed with an anxiety disorder. A brief discussion of selected proposed mechanisms that may underlie relations of exercise and anxiety is also provided. The weight of the available empirical evidence indicates that exercise training reduces symptoms of anxiety among healthy adults, chronically ill patients, and patients with panic disorder. Preliminary data suggest that exercise training can serve as an alternative therapy for patients with social anxiety disorder, generalized anxiety disorder, and obsessive–compulsive disorder. Anxiety reductions appear to be comparable to empirically supported treatments for panic and generalized anxiety disorders. Large trials aimed at more precisely determining the magnitude and generalizability of exercise training effects appear to be warranted for panic and generalized anxiety disorders. Future well-designed randomized controlled trials should (a) examine the therapeutic effects of exercise training among understudied anxiety disorders, including specific phobias, social anxiety disorder and posttraumatic stress disorder; (b) focus on understudied exercise modalities, including resistance exercise training and programs that combine exercise with cognitive-behavioral therapies; and (c) elucidate putative mechanisms of the anxiolytic effects of exercise training.

The Potent Effect of Environmental Context on Relapse to Alcohol-Seeking After Extinction

Environments in which the pharmacological effects of alcohol have been experienced become potent triggers for relapse in abstinent humans. Animal models developed to study the effect of environmental contexts on relapse to alcohol-seeking behavior demonstrate that alcohol-seeking is renewed by exposure to an alcohol-associated context, following the extinction of alcohol-seeking in a different context. Hence, contexts in which alcohol conditioning and extinction learning occur can be critical determinants for whether or not alcohol-seeking behavior is observed. This review summarizes preclinical research to date examining the role of alcohol contexts on the reinstatement of extinguished responding for alcohol. Behavioral studies have elucidated factors that are important for eliciting context-dependent relapse, and have uncovered novel interactions between alcohol-seeking driven by discrete alcohol cues in different contexts. Neuropharmacological studies provide substantial evidence for a role of dopaminergic systems in context-dependent reinstatement, and growing support for opioidergic mechanisms as well. Several key limbic brain regions have been identified in the modulation of alcohol-seeking by context, supporting a proposed neural circuit that includes the hippocampus, nucleus accumbens, basolateral amygdala, lateral hypothalamus, and the paraventricular thalamus.

Oxytocin, motivation and the role of dopamine

The hypothalamic neuropeptide oxytocin has drawn the attention of scientists for more than a century. The understanding of the function of oxytocin has expanded dramatically over the years from a simple peptide adept at inducing uterine contractions and milk ejection to a complex neuromodulator with a capacity to shape human social behavior. Decades of research have outlined oxytocin's ability to enhance intricate social activities ranging from pair bonding, sexual activity, affiliative preferences, and parental behaviors. The precise neural mechanisms underlying oxytocin's influence on such behaviors have just begun to be understood. Research suggests that oxytocin interacts closely with the neural pathways responsible for processing motivationally relevant stimuli. In particular, oxytocin appears to impact dopaminergic activity within the mesocorticolimbic dopamine system, which is crucial not only for reward and motivated behavior but also for the expression of affiliative behaviors. Though most of the work performed in this area has been done using animal models, several neuroimaging studies suggest similar relationships may be observed in humans. In order to introduce this topic further, this paper will review the recent evidence that oxytocin may exert some of its social-behavioral effects through its impact on motivational networks.

mGluR5 is necessary for maintenance of methamphetamine-induced associative learning

Conditioned place preference (CPP) reflects the significance of contextual cues that are associated with rewarding effects of abused drugs such as methamphetamine (Meth). Glutamate neurotransmission is augmented following exposure to stimulants and associated cues. Activation of group I metabotropic glutamate receptors (mGluR) is critical for the acquisition and expression of stimulant-induced CPP. We hypothesized that the maintenance of Meth-induced CPP would also require activated mGluR, and that the role of mGluR1 vs. mGluR5 group I subtypes may differ. To test this hypothesis, negative allosteric modulators (NAMs) of these receptors were administered following the development of Meth-induced CPP. NAMs exert their functional effects by displacing agonist from agonist-occupied receptors, thus NAMs selectively target brain regions with glutamate release. Conditioning with Meth every other day for six days resulted in significant preference for the Meth-paired compartment. Two once-daily injections of the mGluR1 NAM, JNJ16259685 (0.3mg/kg, i.p.) or its vehicle on days 13 and 14 after Meth-conditioning did not influence the maintenance of Meth-induced CPP; however, administration of the mGluR5 NAMs MTEP (3mg/kg, i.p.) and MPEP (30 mg/kg, i.p.) inhibited maintenance processes necessary for CPP to be expressed. These findings suggest a subtype-specific role of mGluR5 receptors in the maintenance of place preference memory and potential of mGluR5 NAMs as a useful target for Meth addiction therapy.

Placebo and the new physiology of the doctor-patient relationship

Modern medicine has progressed in parallel with the advancement of biochemistry, anatomy, and physiology. By using the tools of modern medicine, the physician today can treat and prevent a number of diseases through pharmacology, genetics, and physical interventions. Besides this materia medica, the patient's mind, cognitions, and emotions play a central part as well in any therapeutic outcome, as investigated by disciplines such as psychoneuroendocrinoimmunology. This review describes recent findings that give scientific evidence to the old tenet that patients must be both cured and cared for. In fact, we are today in a good position to investigate complex psychological factors, like placebo effects and the doctor-patient relationship, by using a physiological and neuroscientific approach. These intricate psychological factors can be approached through biochemistry, anatomy, and physiology, thus eliminating the old dichotomy between biology and psychology. This is both a biomedical and a philosophical enterprise that is changing the way we approach and interpret medicine and human biology. In the first case, curing the disease only is not sufficient, and care of the patient is of tantamount importance. In the second case, the philosophical debate about the mind-body interaction can find some important answers in the study of placebo effects. Therefore, maybe paradoxically, the placebo effect and the doctor-patient relationship can be approached by using the same biochemical, cellular and physiological tools of the materia medica, which represents an epochal transition from general concepts such as suggestibility and power of mind to a true physiology of the doctor-patient interaction.

Affective and sensorimotor components of emotional prosody generation

Although advances have been made regarding how the brain perceives emotional prosody, the neural bases involved in the generation of affective prosody remain unclear and debated. Two models have been forged on the basis of clinical observations: a first model proposes that the right hemisphere sustains production and comprehension of emotional prosody, while a second model proposes that emotional prosody relies heavily on basal ganglia. Here, we tested their predictions in two functional magnetic resonance imaging experiments that used a cue-target paradigm, which allows distinguishing affective from sensorimotor aspects of emotional prosody generation. Both experiments show that when participants prepare for emotional prosody, bilateral ventral striatum is specifically activated and connected to temporal poles and anterior insula, regions in which lesions frequently cause dysprosody. The bilateral dorsal striatum is more sensitive to cognitive and motor aspects of emotional prosody preparation and production and is more strongly connected to the sensorimotor speech network compared with the ventral striatum. Right lateralization during increased prosodic processing is confined to the posterior superior temporal sulcus, a region previously associated with perception of emotional prosody. Our data thus provide physiological evidence supporting both models and suggest that bilateral basal ganglia are involved in modulating motor behavior as a function of affective state. Right lateralization of cortical regions mobilized for prosody control could point to efficient processing of slowly changing acoustic speech parameters in the ventral stream and thus identify sensorimotor processing as an important factor contributing to right lateralization of prosody.