Acupuncture,basal a common treatment modality within complementary and alternative medicine, has been widely used for Parkinson's disease (PD). Using functional magnetic one resonance imaging (fMRI), we explored the neural mechanisms underlying the effect of specific and genuine acupuncture treatment on the motor modality function in patients with PD. Three fMRI scans were performed in random order in a block design, one for verum been acupuncture (VA) treatment, another one for a covert placebo (CP), and the third one for an overt placebo (OP) at function the motor function implicated acupoint GB34 on the left foot of 10 patients with PD. We calculated the contrast that activation subtracts the blood-oxygen-level dependent (BOLD) response for the acupuncture effect (VA vs. CP) and the placebo effect (CP vs. OP).the We found a significant improvement in the motor function of the affected hand after acupuncture treatment. The putamen and the a primary motor cortex were activated when patients with PD received the acupuncture treatment (VA vs. CP) and these activations correlated and with individual enhanced motor function. Expectation towards acupuncture modality (CP vs. OP) elicited activation over the anterior cingulate gyrus, the PD superior frontal gyrus, and the superior temporal gyrus. These findings suggest that acupuncture treatment might facilitate improvement in the motor received functioning of patients with PD via the basal ganglia-thalamocortical circuit.(c) 2009 Movement Disorder Society.

INTRODUCTION:which Various experimental manipulations, usually involving drug administration, have been used to produce symptoms of psychosis in healthy volunteers. Different drugs underlying produce both common and distinct symptoms. A challenge is to understand how apparently different manipulations can produce overlapping symptoms. We involving suggest that current Bayesian formulations of information processing in the brain provide a framework that maps onto neural circuitry and symptoms gives us a context within which we can relate the symptoms of psychosis to their underlying causes. This helps us The to understand the similarities and differences across the common models of psychosis. MATERIALS AND METHODS: The Bayesian approach emphasises processing common of information in terms of both prior expectancies and current inputs. A mismatch between these leads us to update inferences this about the world and to generate new predictions for the future. According to this model, what we experience shapes what This we learn, and what we learn modifies how we experience things. DISCUSSION: This simple idea gives us a powerful and and flexible way of understanding the symptoms of psychosis where perception, learning and inference are deranged. We examine the predictions of a the cognitive model in light of what we understand about the neuropharmacology of psychotomimetic drugs and thereby attempt to account deranged. for the common and the distinctive effects of NMDA receptor antagonists, serotonergic hallucinogens, cannabinoids and dopamine agonists. CONCLUSION: By acknowledging to the importance of perception and perceptual aberration in mediating the positive symptoms of psychosis, the model also provides a useful also setting in which to consider an under-researched model of psychosis-sensory deprivation.

Expectations,of positive or negative, are modulating factors influencing behavior. They are also thought to underlie placebo effects, potentially impacting perceptions and placebo-induced biological processes. We used sustained pain as a model to determine the neural mechanisms underlying placebo-induced analgesia and affective changes modulating in healthy humans. Subjects were informed that they could receive either an active agent or an inactive compound, similar to to routine clinical trials. Using PET and the mu-opioid selective radiotracer [(11)C]carfentanil we demonstrate placebo-induced activation of opioid neurotransmission in a prefrontal number of brain regions. These include the rostral anterior cingulate, orbitofrontal and dorsolateral prefrontal cortex, anterior and posterior insula, nucleus a accumbens, amygdala, thalamus, hypothalamus, and periaqueductal grey. Some of these regions overlap with those involved in pain and affective regulation was but also motivated behavior. The activation of endogenous opioid neurotransmission was further associated with reductions in pain report and negative of affective state. Additional studies with the radiotracer [(11)C]raclopride, studies labeling dopamine D2/3 receptors, also demonstrate the activation of nucleus accumbens opioid dopamine during placebo administration under expectation of analgesia. Both dopamine and opioid neurotransmission were related to expectations of analgesia and respond deviations from those initial expectations. When the activity of the nucleus accumbens was probed with fMRI using a monetary reward and expectation paradigm, its activation was correlated with both dopamine, opioid responses to placebo in this region and the formation of also placebo analgesia. These data confirm that specific neural circuits and neurotransmitter systems respond to the expectation of benefit during placebo neurotransmitter administration, inducing measurable physiological changes.

BACKGROUND::modulation Over the last decades, remarkable progresses have been accomplished regarding the understanding of the neurophysiologic and neuropharmacological bases of pain.We A growing preclinical literature supports a role for substance P, endogenous opioids, glutamate, serotonin, and norepinephrine in pain perception. Recently,remarkable a series of studies explored the function of dopamine in pain perception, which we review here, while focusing on human understanding studies. METHODS:: The literature was screened using electronic databases. RESULTS:: We found evidence from genetics, brain imaging, neuropsychiatry, and pharmacology positron of an involvement of dopamine in pain processing. Using positron emission tomography and molecular genetics, studies have been performed in we healthy volunteers and patients suffering from chronic pain conditions, showing a key role of dopamine in pain perception. Moreover, abnormal in pain perception has been documented in neuropsychiatric disorders, such as Parkinson's disease and schizophrenia, where dopamine has a pathophysiological role.evidence Lastly, pharmacological studies have shown that dopaminergic drugs (antipsychotics, antiparkinsonian drugs, atypical antidepressants, psychostimulants) modify pain perception. DISCUSSION:: Although there pain is growing evidence supporting a role of dopamine in pain perception, the mechanisms by which dopamine influences pain processing remains with to be determined. On the basis of preliminary findings, we put forth the hypothesis that dopamine is involved in endogenous supporting pain modulation systems, and further discuss the implications of this hypothesis for the understanding of the physiopathology of chronic pain regarding disorders associated with dysfunctional endogenous pain modulation systems. Synapse 63:390-402, 2009.(c) 2009 Wiley-Liss, Inc.

Placebos role have been shown to induce powerful effects in a variety of medical conditions, such as pain and movement disorders, as suggestion well as to increase physical performance and endurance in healthy subjects. Here we investigated the effects of an ergogenic placebo induce on the performance of the quadriceps muscle, which is responsible for the extension of the leg relative to the thigh.conditions, In a first experiment, a placebo was administered along with the suggestion that it was caffeine at high dose. This subjects, resulted in a significant increase in mean muscle work across subjects, which, however, was not accompanied by a decrease of the perceived muscle fatigue. In a second experiment, the placebo caffeine was administered twice in two different sessions. Each time, the quadriceps weight to be lifted with the quadriceps was reduced surreptitiously so as to make the subjects believe that the 'ergogenic it agent' was effective. After this conditioning procedure, the load was restored to the original weight, and both muscle work and performance, perceived fatigue assessed after placebo administration. Compared with the first experiment, the placebo effect was larger, with a significant increase second in muscle work and decrease in perceived muscle fatigue. Within the context of the role of peripheral and/or central mechanisms placebo in muscle performance, the present findings suggest a central mechanism of top-down modulation of muscle fatigue. In addition, the difference variety between the first and second experiment underscores the role of learning in increasing muscle performance with placebos.

Relief ratings from pain in humans is frequently measured by computing the reduction on an 11-point pain intensity scale. However, this definition of of relief may be insufficient to capture the utility of pain relief for the individual. Based on pain literature and is evidence from studies examining relief and reward, it is clear that pain relief is a broad concept comprising several factors,an only one of which is pain intensity reduction. According to opponent process theory, all sensations consist of a primary process deviation and a slow 'opponent process' of opposite valence, the purpose of which is to reduce the deviation from homeostatic balance.that Here, opponent process theory provided a framework to explore the interaction between pain, relief and reward. We devised three psychophysical pain studies examining the temporal (Experiment I) and magnitude (Experiments I and II) relationships between pain severity and its subsequent relief.a In Experiment III, we further manipulated the magnitude and pleasantness of relief experienced by applying innocuous cooling following noxious heat significantly stimulation of capsaicin-sensitized skin. Results confirmed predictions from opponent process theory and showed that pain intensity reduction was significantly stronger the than relief intensity ratings. Furthermore, continuous relief ratings appeared to reflect the speed of pain intensity reduction. Varying pain intensity pain parametrically confirmed that relief increases with pain intensity. That innocuous cooling following primary hyperalgesia intervention significantly increased the intensity, pleasantness reduction and duration of relief provides further evidence that pain relief encapsulates more than a reduction in pain intensity. Importantly, the intensity. high relief pleasantness ratings confirmed the hypothesized link between relief and reward.

RATIONALE:to Although opiate antagonists have shown promise in the treatment of pathological gambling (PG), individual responses vary. No studies have systematically double-blind examined predictors of medication treatment outcome in PG. Understanding clinical variables related to treatment outcome should help generate treatment algorithms shown for PG. OBJECTIVE: We sought to identify clinical variables associated with treatment outcome in PG subjects receiving opiate antagonists. MATERIALS individual AND METHODS: Two hundred eighty-four subjects [137 (48.2%) women] with DSM-IV PG were treated in one of two double-blind placebo-controlled Obsessive trials (16 weeks of nalmefene or 18 weeks of naltrexone). Gambling severity was assessed with the Yale Brown Obsessive Compulsive (p Scale Modified for Pathological Gambling (PG-YBOCS) with positive response defined as >/=35% reduction in PG-YBOCS score for at least 1 identify month by study endpoint. Depression, anxiety, and psychosocial functioning were included in stepwise logistic regression analyses designed to identify clinical placebo-controlled factors independently associated with treatment response. RESULTS: The clinical variable most strongly associated with a positive response to an opiate trend antagonist was a positive family history of alcoholism (p = .006). Among individuals receiving higher doses of opiate antagonists (i.e.,PG. nalmefene 50 or 100 mg/day or naltrexone 100 or 150 mg/day), intensity of gambling urges (PG-YBOCS urge subscale) was associated (i.e., with a positive response on a trend level (p = .036). Among individuals receiving placebo, younger age was associated, on pathological a trend level, with positive treatment outcome (p = .012). CONCLUSIONS: A family history of alcoholism appears to predict response in to an opiate antagonist in PG. Future research is needed to identify specific factors (e.g., genetic) mediating favorable responses.

Placebo into effects are beneficial health outcomes not related to the relatively direct biological effects of an intervention and can be elicited was by an agent that, by itself, is inert. Understanding these placebo effects will help to improve clinical trial design, especially health for interventions such as surgery, CNS-active drugs and behavioural interventions which are often non-blinded. A literature review was performed to relatively retrieve articles discussing placebo implications of clinical trials, the neurobiology of placebo effects and the implications of placebo effect for effects several disorders of neurological relevance. Recent research in placebo analgesia and other conditions has demonstrated that several neurotransmitter systems, such and as opiate and dopamine, are involved with the placebo effect. Brain regions including anterior cingulate cortex, dorsolateral prefrontal cortex and opiate basal ganglia have been activated following administration of placebo. A patient's expectancy of improvement may influence outcomes as much as performed some active interventions and this effect may be greater for novel interventions and for procedures. Maximizing this expectancy effect is clinicians important for clinicians to optimize the health of their patient. There have been many relatively acute placebo studies that are now now being extended into clinically relevant models of placebo effect.

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

PURPOSE eventually OF REVIEW: The placebo literature has substantially increased in 2006 and 2007, and more and more medical and psychological subspecialties (Pavlovian) have added empirical data to our knowledge. RECENT FINDINGS: The theoretical framework of our understanding of the placebo response needs The extension to account for findings that cannot be attributed to (Pavlovian) conditioning or suggestions alone. In addition, imaging studies need in to address individual responses rather than group means, and to expand beyond experimental pain research. Gender aspects have been demonstrated responses for the placebo response but still widely ignored, especially in neurophysiological studies. It has been shown that nocebo research needs used a methodological and ethical framework that allows its exploration. Finally, analyses of clinical trial data, either as metaanalyses or as in reanalyses of trial raw data, may allow us to identify factors that subsequently can be used in experimental work. SUMMARY:conditioning Novel findings will allow better planning of clinical drug trials, better handling of clinical trial data in the future, and allow finally, may eventually result in improved patient management.

CONTEXT:of Placebo and nocebo effects, the therapeutic and adverse effects, respectively, of inert substances or sham procedures, represent serious confounds in properties. the evaluation of therapeutic interventions. They are also an example of cognitive processes, particularly expectations, capable of influencing physiology. OBJECTIVE:therapeutic To examine the contribution of 2 different neurotransmitters, the endogenous opioid and the dopaminergic (DA) systems, to the development of procedures, placebo and nocebo effects. DESIGN AND SETTING: Using a within-subject design, subjects twice underwent a 20-minute standardized pain challenge, in MEASURES: the absence and presence of a placebo with expected analgesic properties. Studies were conducted in a university hospital setting. PARTICIPANTS:and Twenty healthy men and women aged 20 to 30 years recruited by advertisement. MAIN OUTCOME MEASURES: Activation of DA and Placebo-induced opioid neurotransmission by a pain stressor with and without placebo (changes in the binding potential of carbon 11 [(11)C]-labeled raclopride were and [(11)C] carfentanil with positron emission tomography) and ratings of pain, affective state, and anticipation and perception of analgesia. RESULTS:analgesic Placebo-induced activation of opioid neurotransmission was detected in the anterior cingulate, orbitofrontal and insular cortices, nucleus accumbens, amygdala, and periaqueductal in gray matter. Dopaminergic activation was observed in the ventral basal ganglia, including the nucleus accumbens. Regional DA and opioid activity of were associated with the anticipated and subjectively perceived effectiveness of the placebo and reductions in continuous pain ratings. High placebo substances responses were associated with greater DA and opioid activity in the nucleus accumbens. Nocebo responses were associated with a deactivation areas of DA and opioid release. Nucleus accumbens DA release accounted for 25% of the variance in placebo analgesic effects. CONCLUSIONS:deactivation Placebo and nocebo effects are associated with opposite responses of DA and endogenous opioid neurotransmission in a distributed network of regions. regions. The brain areas involved in these phenomena form part of the circuit typically implicated in reward responses and motivated DA behavior.

Positron challenge Emission Tomography (PET) with appropriate radiotracers and quantification methods allows the detection of changes in endogenous neurotransmission by determine the repeated reduction in the binding potential (BP) of receptors before and after experimental challenges. These have typically employed psychostimulants and PET appropriate with dopamine (DA) receptor radiotracers. However, reductions in BP persist far beyond the increases in the release of the endogenous of neurotransmitter, an effect ascribed to receptor internalization and recycling, a possible confound in repeated studies. Here we examined the time-course shown of changes in BP during a nonpharmacological challenge, moderate levels of sustained pain, shown to induce robust reductions in mu-opioid persist and DA D2 BP, as measured with [(11)C]carfentanil and [(11)C]raclopride. It was hypothesized that, contrary to pharmacological probes, the use persistent of a more "physiological" stimulus would not be associated with persistent changes in the BP measures. The pain challenge was Here associated with reductions in mu-opioid receptor BP in several cortical and subcortical regions. These did not persist in a subsequent pharmacological scan. Similar results were obtained for DA D2 receptor BP, where the pain challenge induced significant reductions in the caudate on nucleus. These data demonstrate that changes in receptor BP induced by a nonpharmacological challenge did not persist into subsequent scans.BP, They further suggest differences in the effect of pharmacological and nonpharmacological probes on PET BP measures. These may reflect varying the levels of change in receptor affinity, receptor internalization, and recycling depending on the type of challenge employed. Synapse 61:707-714, 2007.recycling (c) 2007 Wiley-Liss, Inc.

In and addition to its involvement in motor control and in encoding reward value, increasing evidence also implicates basal ganglia dopaminergic mechanisms the in responses to stress and aversive stimuli. Basal ganglia dopamine (DA) neurotransmission may then respond to environmental events depending on involvement their saliency, orienting the subsequent responses of the organism to both positive and negative stimuli. Here we examined the involvement reward of DA neurotransmission in the human response to pain, a robust physical and emotional stressor across species. Positron emission tomography the with the DA D(2) receptor antagonist radiotracer [(11)C]raclopride detected significant activation of DA release in dorsal and ventral regions of fear the basal ganglia of healthy volunteers. Activation of nigrostriatal (dorsal nucleus caudate and putamen) DA D(2) receptor-mediated neurotransmission was positively DA associated with individual variations in subjective ratings of sensory and affective qualities of the pain. In contrast, mesolimbic (nucleus accumbens)human DA activation, which may impact on both D(2) and D(3) receptors, was exclusively associated with variations in the emotional responses neurotransmission of the individual during the pain challenge (increases in negative affect and fear ratings). These data demonstrate that basal ganglia levels dopamine D(2) receptor-mediated neurotransmission is involved in responses to pain and that it contributes to individual variations in the pain and experience at the levels of physical and emotional elements, albeit with different neuroanatomical substrates.

Reductions receptor in pain ratings when administered a placebo with expected analgesic properties have been described and hypothesized to be mediated by in the pain-suppressive endogenous opioid system. Using molecular imaging techniques, we directly examined the activity of the endogenous opioid system on ratings mu-opioid receptors in humans in sustained pain with and without the administration of a placebo. Significant placebo-induced activation of mu-opioid with receptor-mediated neurotransmission was observed in both higher-order and sub-cortical brain regions, which included the pregenual and subgenual rostral anterior cingulate,placebo-induced the dorsolateral prefrontal cortex, the insular cortex, and the nucleus accumbens. Regional activations were paralleled by lower ratings of pain demonstrate intensity, reductions in its sensory and affective qualities, and in the negative emotional state of the volunteers. These data demonstrate anterior that cognitive factors (e.g., expectation of pain relief) are capable of modulating physical and emotional states through the site-specific activation sustained of mu-opioid receptor signaling in the human brain.

This this is a pilot examination of the hypothesis that some of the effects of smoking cigarettes in humans are mediated through were nicotine activation of opioid and dopamine (DA) neurotransmission. Neuroimaging was performed using positron emission tomography and the radiotracers [(11)C]carfentanil and of [(11)C]raclopride, labeling mu-opioid and DA D2 receptors, respectively. Six healthy male smokers were abstinent overnight. After radiotracer administration, subjects smoked of two denicotinized cigarettes, followed 45 min later by two average nicotine cigarettes. Dynamic data were acquired over 90 min, and low transformed into parametric maps of receptor availability in vivo (binding potential, BP), corresponding to low and high nicotine smoking periods amygdala. and analyzed on a voxel-by-voxel basis using SPM'99 and correction for multiple comparisons. Significant activation of mu-opioid receptor-mediated neurotransmission from cingulate denicotinized to average nicotine conditions was observed in the right anterior cingulate cortex. DA D2 neurotransmission was activated in the over ventral basal ganglia, correlating with Fagerström scale nicotine dependence scores. Lower mu-opioid receptor BP was also detected during the denicotinized DA smoking condition in the smoker group, compared to baseline scans in non-smokers, in the cingulate cortex, thalamus, ventral basal ganglia,the and amygdala. These reductions were reversed during the average nicotine condition in the thalamus, ventral basal ganglia and amygdala. These non-smokers, data point to both the feasibility of simultaneously examining opioid and DA neurotransmission responses to smoking in humans, as well the as to the need to examine non-nicotine aspects of smoking to more fully understand the behavioral effects of this drug.Neuropsychopharmacology fully advance online publication, 8 November 2006; doi:10.1038/sj.npp.1301238.

Prominent responses interindividual and sex-dependent differences have been described in responses to sustained pain and other stressful stimuli. Variations in mu-opioid receptor-mediated healthy endogenous opioid neurotransmission may underlie some of these processes. We examined both baseline mu-opioid receptor levels and the activation of differences this neurotransmitter system during sustained pain using positron emission tomography in a sample of young healthy men and women. Women to were studied twice, during low and high estrogen states. The high-estrogen state was associated with regional increases in baseline mu-opioid high-estrogen receptor availability in vivo and a greater activation of endogenous opioid neurotransmission during the pain stressor. The latter did not sensory differ from that obtained in males. During the low estrogen condition, however, significant reductions in endogenous opioid tone were observed not at the level of thalamus, nucleus accumbens, and amygdala, which were associated with hyperalgesic responses. Estrogen-associated variations in the activity and of mu-opioid neurotransmission correlated with individual ratings of the sensory and affective perceptions of the pain and the subsequent recall recall of that experience. These data demonstrate a significant role of estrogen in modulating endogenous opioid neurotransmission and associated psychophysical responses and to a pain stressor in humans.

The account activation of pain-suppressive, endogenous opioid neurotransmission after administration of a placebo with expectation of analgesia has been directly demonstrated in the humans using molecular imaging techniques in recent work. Regional effects were described in the dorsolateral prefrontal cortex, pregenual anterior cingulate,opioid anterior insula, and nucleus accumbens. However, it was also observed that the magnitude of these responses was subject to substantial of individual and regional variation. The present study was undertaken to examine the contribution of various factors to the observed variability males in the neurochemical responses to placebo administration. Multiple regression analyses were conducted on data from 19 healthy males to study elements, to what degree expectations of analgesia and various elements of the experience of pain itself, in the absence of placebo,A were associated with the individual and brain regional variability in endogenous opioid neurochemical responses to placebo. A model that included observed affective qualities of pain, the volume of algesic stimulus required to maintain pain over the experimental period within a moderate measure range, and the internal affective state of the volunteers contributed to 40-68% of the variance in the regional neurochemical responses will to placebo. These initial data suggests that in the case of endogenous opioid mediated placebo analgesic responses, the individual experience regional of pain, in particular its affective elements, the internal affective state of the individuals during pain and a measure of placebo sustained pain sensitivity are important factors contributing to the formation of a placebo effect. Further examination of individual variations in responding placebo responding will need to take into account the underlying process for which relief is required.

Responses pain to pain and other stressors are regulated by interactions between multiple brain areas and neurochemical systems. We examined the influence of of a common functional genetic polymorphism affecting the metabolism of catecholamines on the modulation of responses to sustained pain in pain humans. Individuals homozygous for the met158 allele of the catechol-O-methyltransferase (COMT) polymorphism (val158met) showed diminished regional mu-opioid system responses to are pain compared with heterozygotes. These effects were accompanied by higher sensory and affective ratings of pain and a more negative the internal affective state. Opposite effects were observed in val158 homozygotes. The COMT val158met polymorphism thus influences the human experience of thus pain and may underlie interindividual differences in the adaptation and responses to pain and other stressful stimuli.

Sex response differences in the experience of clinical and experimental pain have been reported. However, the neurobiological sources underlying the variability in in pain responses between sexes have not been adequately explored, especially in humans. The endogenous opioid neurotransmitters and mu-opioid receptors are of centrally implicated in responses to stress, in the suppression of pain, and in the action of opiate analgesic drugs. Here However, we examined sex differences in the activation of the mu-opioid system in response to an intensity-controlled sustained deep-tissue pain challenge young with positron emission tomography and a mu-opioid receptor-selective radiotracer. Twenty-eight young healthy volunteers (14 men and 14 women) were studied previously during saline control and pain conditions using a double-blind, randomized, and counterbalanced design. Women were scanned during the early follicular ovulatory phase of their menstrual cycles after ovulatory cycles. Significant sex differences in the regional activation of the mu-opioid system in to response to sustained pain were detected compared with saline controls. Men demonstrated larger magnitudes of mu-opioid system activation than women experimental in the anterior thalamus, ventral basal ganglia, and amygdala. Conversely, women demonstrated reductions in the basal state of activation of magnitude the mu-opioid system during pain in the nucleus accumbens, an area previously associated with hyperalgesic responses to the blockade of basal opioid receptors in experimental animals. These data demonstrate that at matched levels of pain intensity, men and women during their been follicular phase differ in the magnitude and direction of response of the mu-opioid system in distinct brain nuclei.

CONTEXT:the The endogenous opioid system and opioid mu receptors (mu-receptors) are known to interface environmental events, positive (eg, relevant emotional stimuli)positron and negative (eg, stressors), with pertinent behavioral responses and to regulate motivated behavior. OBJECTIVE: To examine the degree to which opioid trait impulsiveness (the tendency to act on cravings and urges rather than to delay gratification) is predicted by baseline mu-receptor positive availability or the response of this system to a standardized, experientially matched stressor. DESIGN, SETTING, AND PATIENTS: Nineteen young healthy of male volunteers completed a personality questionnaire (NEO Personality Inventory, Revised) and underwent positron emission tomography scans with the mu-receptor-selective radiotracer traits. carfentanil labeled with carbon 11. Measures of receptor concentrations were obtained at rest and during receipt of an experimentally maintained (deliberation) pain stressor of matched intensity between subjects. MAIN OUTCOME MEASURES: Baseline receptor levels and stress-induced activation of mu-opioid system neurotransmission tomography compared between subjects scoring above and below the population median on the NEO Personality Inventory, Revised, impulsiveness subscale and the that orthogonal dimension (deliberation) expected to interact with it. RESULTS: High impulsiveness and low deliberation scores were associated with significantly higher disorders) regional mu-receptor concentrations and greater stress-induced endogenous opioid system activation. Effects were obtained in the prefrontal and orbitofrontal cortices, anterior behavior cingulate, thalamus, nucleus accumbens, and basolateral amygdala-all regions involved in motivated behavior and the effects of drugs of abuse. Availability environmental of the mu-receptor and the magnitude of stress-induced endogenous opioid activation in these regions accounted for 17% to 49% of (eg, the variance in these personality traits. CONCLUSIONS: Individual differences in the function of the endogenous mu-receptor system predict personality traits these that confer vulnerability to or resiliency against risky behaviors such as the predisposition to develop substance use disorders. These personality in traits are also implicated in psychopathological states (eg, personality disorders) in which variations in the function of this neurotransmitter system to also may play a role.

Placebo and has been reported to exert beneficial effects in patients regarding the treatment of pain. Human functional neuroimaging technology can study neural the intact human brain to elucidate its functional neuroanatomy and the neurobiological mechanism of the placebo effect. Blood flow measurement to using functional magnetic resonance imaging and positron emission tomography (PET) has revealed that analgesia is related to decreased neural activities regarding in pain-modulatory brain regions, such as the rostral anterior cingulate cortex (rACC), insula, thalamus, and brainstem including periaqueductal gray (PAG)thalamus, and ventromedial medulla. The endogenous opioid system and its activation of mu-opioid receptors are thought to mediate the observed effects to of placebo. The mu-opioid receptor-selective radiotracer-labeled PET studies show that the placebo effects are accompanied by reduction in activation of The opioid neural transmission in pain-sensitive brain regions, including rACC, prefrontal cortex, insula, thalamus, amygdala, nucleus accumbens (NAC) and PAG. Further activities PET studies with dopamine D2/D3 receptor-labeling radiotracer demonstrate that basal ganglia including NAC are related to placebo analgesic responses. NAC analgesia dopamine release induced by placebo analgesia is related to expectation of analgesia. These data indicate that the aforementioned brain regions as and neurotransmitters such as endogenous opioid and dopamine systems contribute to placebo analgesia.

The relationship experience of a sensory event is extensively shaped by past experience and expectations. Placebo analgesia, one of the most studied was models of expectation-mediated effects, can be induced by suggestion of analgesia and conditioning. The present study examined the possibility that event sleep might contribute to the consolidation of new expectations and consequently influence the generation of expectation-mediated placebo effects. Strong expectations expectations. of analgesia were generated before sleep by conditioning manipulations wherein the intensity of thermal pain stimulation was surreptitiously reduced after morning the application of a topical placebo cream. Expectations and placebo analgesic effects were measured the following morning and compared with of those of a control daytime group without sleep. Although placebo effects were observed in both groups, correlation analysis suggests that Moreover, the mediating effect of expectations on placebo responses was strongest in the overnight group. Moreover, after exposure to a convincing surreptitiously analgesia experience, the relative duration of rapid eye movement (REM) sleep decreased in subjects showing higher analgesic expectations and placebo the responses the next morning. In a third group exposed to less consistent analgesic experiences before sleep, expectations reported in the may morning were comparable with other groups. However, expectations were positively correlated with REM sleep and did not emerge as a before significant mediator of the analgesic effect. Together, these findings show that sleep-related processes may influence the association between expectations and experience placebo analgesia and that REM sleep can predict placebo-induced expectations of pain relief. However, equivocal previous experience with treatments may with significantly alter the relationship between relief expectation, REM sleep, and placebo effects.

The show anticipation of clinical benefit, a crucial component of placebo analgesia, has been suggested to be a special case of reward placebo anticipation. Since reward processing is closely linked to the ventral striatum and the neurotransmitter dopamine, we examined the relationships between clinical brain gray matter, placebo analgesic response, and personality traits associated with dopaminergic neurotransmission. We report that dopamine-related traits predict a component substantial portion of the pain relief an individual gains from a sham treatment. Voxel-based morphometry of magnetic resonance images shows report that the magnitude of placebo analgesia is related to gray matter density (GMD) in several brain regions, including the ventral to striatum, insula, and prefrontal cortex. Similarly, GMD in ventral striatum and prefrontal cortex is related to dopamine-related personality traits. Our magnetic findings highlight the relationship between placebo and reward and potentially offer ways of identifying subjects who are likely to show analgesic large placebo analgesic responses.

Expectations,of positive or negative, are modulating factors influencing behavior. They are also thought to underlie placebo effects, potentially impacting perceptions and placebo-induced biological processes. We used sustained pain as a model to determine the neural mechanisms underlying placebo-induced analgesia and affective changes modulating in healthy humans. Subjects were informed that they could receive either an active agent or an inactive compound, similar to to routine clinical trials. Using PET and the mu-opioid selective radiotracer [(11)C]carfentanil we demonstrate placebo-induced activation of opioid neurotransmission in a prefrontal number of brain regions. These include the rostral anterior cingulate, orbitofrontal and dorsolateral prefrontal cortex, anterior and posterior insula, nucleus a accumbens, amygdala, thalamus, hypothalamus, and periaqueductal grey. Some of these regions overlap with those involved in pain and affective regulation was but also motivated behavior. The activation of endogenous opioid neurotransmission was further associated with reductions in pain report and negative of affective state. Additional studies with the radiotracer [(11)C]raclopride, studies labeling dopamine D2/3 receptors, also demonstrate the activation of nucleus accumbens opioid dopamine during placebo administration under expectation of analgesia. Both dopamine and opioid neurotransmission were related to expectations of analgesia and respond deviations from those initial expectations. When the activity of the nucleus accumbens was probed with fMRI using a monetary reward and expectation paradigm, its activation was correlated with both dopamine, opioid responses to placebo in this region and the formation of also placebo analgesia. These data confirm that specific neural circuits and neurotransmitter systems respond to the expectation of benefit during placebo neurotransmitter administration, inducing measurable physiological changes.

The it ventral tegmental area (VTA), the prefrontal cortex and the nucleus accumbens (NAc) are key elements of the mesolimbic dopaminergic system.subtype) Dopaminergic neurotransmission in the NAc is essential in the regulation of motor activity and reward. Extracellular ATP by activating P2 the receptors may function as a neurotransmitter or a neuromodulator. We showed that P2 receptors are expressed both in the NAc (NAc) and VTA, and their activation (probably of the P2Y1 subtype) results in increased dopamine release. It leads to complex neurophysiologic EEG: and behavioral changes. We observed activation of the EEG: an elevation of the absolute EEG power and the power in enhancement the alpha-frequency band as well as decrease in the delta-frequency band. Behavioral studies demonstrated that activation of P2 receptors elicited stronger more consistent and stronger goal-directed locomotor activity in response to the stimulus of a novel environment. P2Y receptors were also in involved in regulation of feeding, their inhibition decreased the amount and the duration of feeding. On the other hand, in changes various behavioral functions, P2 receptor-mediated glutamate release or the activation of the adenosine receptors counterbalanced the actions mediated by ATP-induced P2Y dopamine release. We also showed that enhancement of the P2Y1 receptor expression may be involved in adaptive changes of the various mesolimbic system such as behavioral sensitization to repeated amphetamine administration. In summary, the mesolimbic dopaminergic system is modulated via P2Y nucleus purinergic receptors, and it may lead to complex behavioral pharmacological changes.

Expectations of have been shown to be powerful modulators of pain [1] and emotion [2] in placebo studies. In such experiments, expectations stimulation are induced by instructions combined with manipulation of the sensory experience that is unknown to the subjects. After an expectation shown learning phase where a painful stimulation is surreptitiously lowered following placebo application, the placebo effectively reduces subjective pain intensity in of a subsequent test phase [3]. The strength of this placebo effect is closely related to the induced expectation [4]. Here,intensity we asked whether this powerful cognitive bias reflects a general property of sensory information processing and tested whether the contents of of visual awareness could be altered by a placebo-like expectation manipulation. We found a dramatic effect of experimentally induced expectations asked on the perception of an ambiguous visual motion stimulus. This shows that expectations have a strong and general influence on is our experience of the sensory input independently of its specific type and content.

Pain pain and relief are at opposite ends of the reward-aversion continuum. Studying them provides an opportunity to evaluate dynamic changes in to brain activity in reward-aversion pathways as measured by functional magnetic resonance imaging (fMRI). Of particular interest is the nucleus accumbens are (NAc), a brain substrate known to be involved in reward-aversion processing, whose activation valence has been observed to be opposite the in response to reward or aversive stimuli. Here we have used pain onset (aversive) and pain offset (rewarding) involving a to prolonged stimulus applied to the dorsum of the hand in 10 male subjects over 120s to study the NAc fMRI NAc response. The results show a negative signal change with pain onset and a positive signal change with pain offset in prolonged the NAc contralateral to the stimulus. The study supports the idea that the NAc fMRI signal may provide a useful be marker for the effects of pain and analgesia in healthy volunteers.

Placebo a analgesia is one of the most robust and best-studied placebo effects. With the help of brain imaging tools, such as may positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), our understanding of the brain's role in placebo analgesia has one been greatly expanded. Previous studies suggest that multiple mechanisms may underlie the phenomenon of placebo analgesia. This review posits a best-studied theoretical framework for interpreting the results of the neuroimaging literature of placebo analgesia. According to this framework, placebo treatment may for exert an analgesic effect on at least three stages of pain processing, by 1) influencing pre-stimulus expectation of pain relief,may 2) modifying pain perception, and 3) distorting post-stimulus pain rating. Importantly, change in one such stage may hasten change in three another, and furthermore, contribution from any or all of the three stages may vary by circumstance, or between individuals. The underlie literature suggests that multiple brain regions, including the anterior cingulate cortex, anterior insula, prefrontal cortex and periaqueductal grey, play a suggests pivotal role in these processes.

Transmission regulation.Neuropsychopharmacology of reward signals is a function of dopamine, a neurotransmitter known to be involved in the mechanism of psychosis. Using healthy functional magnetic resonance imaging (fMRI), we investigated how expectation and receipt of monetary rewards modulate brain activation in patients with a bipolar mania and schizophrenia. We studied 12 acutely manic patients with a history of bipolar disorder, 12 patients with a to current episode of schizoaffective disorder or schizophrenia and 12 healthy subjects. All patients were treated with dopamine antagonists at the delayed time of the study. Subjects performed a delayed incentive paradigm with monetary reward in the scanner that allowed for investigating for effects of expectation, receipt, and omission of rewards. Patients with schizophrenia and healthy control subjects showed the expected activation of areas, dopaminergic brain areas, that is, ventral tegmentum activation upon expectation of monetary rewards and nucleus accumbens activation during receipt vs subjects. omission of rewards. In manic patients, however, we did not find a similar pattern of brain activation and the differential of signal in the nucleus accumbens upon receipt vs omission of rewards was significantly lower compared to the healthy control subjects.and Our findings provide evidence for abnormal function of the dopamine system during receipt or omission of expected rewards in bipolar the disorder. These deficits in prediction error processing in acute mania may help to explain symptoms of disinhibition and abnormal goal neurotransmitter pursuit regulation.Neuropsychopharmacology advance online publication, 7 November 2007; doi:10.1038/sj.npp.1301620.

Expectations,the positive or negative, are modulating factors influencing behavior. They are also thought to underlie placebo effects, impacting perceptions and biological involved processes. Using healthy human subjects, we examined the role of the nucleus accumbens (NAC), a region centrally involved in the or encoding of reward expectation, in the formation of placebo responses. Employing functional molecular imaging, activation of NAC dopamine (DA) release influencing was observed during placebo administration and related to its anticipated effects, perception-anticipation mismatches, and placebo effect development. In additional functional placebo MRI studies, the expectation of monetary gain increased NAC synaptic activity in a manner proportional to placebo-induced DA release, anticipated differentials, effects, perception-anticipation differentials, and actual placebo effects. Individual variations in NAC response to reward expectation accounted for 28% of the to variance in the formation of placebo analgesia.