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Query: UMLS:C0030567 (Parkinson's disease)
 63,064 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Neuroimaging studies have provided a major contribution to our understanding of the mechanisms of the placebo effect in neurological and psychiatric disorders. Expectation of symptom improvement has long been believed to play a critical role in the placebo effect, and is associated with increased endogenous striatal dopamine release in Parkinson's disease and increased endogenous opioid transmission in placebo analgesia. Evidence from positron emission tomography and functional magnetic resonance imaging studies suggests that expectations of symptom improvement are driven by frontal cortical areas, particularly the dorsolateral prefrontal, orbitofrontal, and anterior cingulate cortices. The ventral striatum is involved in the expectation of rewarding stimuli and, together with the prefrontal cortex, has also been shown to play an important role in the placebo-induced expectation of therapeutic benefit. Understanding the mechanisms of the placebo effect has important implications for treatment of several medical conditions, including depression, pain, and Parkinson's disease.
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PMID:Understanding the placebo effect: contributions from neuroimaging. 2751 74

This article reviews neuroimaging studies of conscious and voluntary regulation of various emotional states (sexual arousal, sadness, negative emotion). The results of these studies show that metacognition and cognitive recontextualization selectively alters the way the brain processes and reacts to emotional stimuli. Neuroimaging studies of the effect of psychotherapy in patients suffering from diverse forms of psychopathology (obsessive-compulsive disorder, panic disorder, unipolar major depressive disorder, social phobia, spider phobia, borderline personality) are also examined. The results of these studies indicate that the mental functions and processes involved in diverse forms of psychotherapy exert a significant influence on brain activity. Neuroimaging investigations of the placebo effect in healthy individuals (placebo analgesia, psychostimulant expectation) and patients with Parkinson's disease or unipolar major depressive disorder are also reviewed. The results of these investigations demonstrate that beliefs and expectations can markedly modulate neurophysiological and neurochemical activity in brain regions involved in perception, movement, pain, and various aspects of emotion processing. Collectively, the findings of the neuroimaging studies reviewed here strongly support the view that the subjective nature and the intentional content (what they are "about" from a first-person perspective) of mental processes (e.g., thoughts, feelings, beliefs, volition) significantly influence the various levels of brain functioning (e.g., molecular, cellular, neural circuit) and brain plasticity. Furthermore, these findings indicate that mentalistic variables have to be seriously taken into account to reach a correct understanding of the neural bases of behavior in humans. An attempt is made to interpret the results of these neuroimaging studies with a new theoretical framework called the Psychoneural Translation Hypothesis.
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PMID:Mind does really matter: evidence from neuroimaging studies of emotional self-regulation, psychotherapy, and placebo effect. 1734 30

The potential of placebo treatments to alleviate a variety of medical conditions has long been recognised. Although the placebo effect is widely known, the physiological mechanisms underlying this phenomenon are not well understood. This review focuses on the existing evidence for placebo responses in different neurological conditions, including pain, Parkinson's disease, depression, sleep and immune-mediated disorders. Special attention is paid to the neural changes associated with placebo treatments, as revealed by in vivo neurophysiological and functional neuroimaging studies. Converging evidence suggests that placebo analgesia is linked to the activation of the endogenous opioid analgesia network, whilst dopaminergic pathways seem to play a central role in the placebo effect in movement disorders and neuroimmunomodulation. Further research on the placebo response is needed, both to improve the efficacy of its application in clinical practice and to shed more light on the complexity of mind-body interactions.
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PMID:Brain mechanisms underlying the placebo effect in neurological disorders. 1763 11

Recent insights have demonstrated a central role for dopaminergic neurotransmission in modulating pain perception and natural analgesia within supraspinal regions, including the basal ganglia, insula, anterior cingulate cortex, thalamus and periaqueductal gray. In addition, while the participation of serotonin and norepinephrine in spinal descending inhibition of pain is well known, a critical role for dopamine in descending inhibition has also been demonstrated. Decreased levels of dopamine likely contribute to the painful symptoms that frequently occur in Parkinson's disease. Moreover, abnormalities in dopaminergic neurotransmission have been objectively demonstrated in painful clinical conditions, including burning mouth syndrome, fibromyalgia and restless legs syndrome. Evidence from animal models and indirect evidence from pharmaceutical trials also suggest a role for dopamine in chronic regional pain syndrome and painful diabetic neuropathy. Several novel classes of medication with analgesic properties have bearing on dopaminergic activity as evident in the capacity of dopamine antagonists to attenuate their analgesic capacity. An expanded appreciation for the role of dopamine in natural analgesia provides the impetus for further study involving preclinical models and advanced neuroimaging techniques in humans, which may lead to the development of novel therapeutic strategies.
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PMID:Role of central dopamine in pain and analgesia. 1845 35

Placebo and nocebo effects are interesting and complex phenomena. In this article, I discuss some findings about the psychological and neurobiological processes that may underlie these effects on the basis of studies of pain, Parkinson's disease, and depression. From a psychological perspective, expectancy and conditioning theories have been used to explain placebo and nocebo effects. These psychological processes may be translated into physiological effects through overlapping brain circuits that are important for cognitive information processing, analgesia, and reward expectations. These brain circuits may represent a fundamentally important common underlying pathway that mediates placebo and nocebo effects in many conditions. Understanding these effects is important for designing clinical treatment studies and interpreting their results and is highly relevant for clinical practices.
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PMID:Understanding the placebo effect. Part 2: underlying psychological & neurobiological processes. 1859 54

Placebo (PL) treatment is a method utilized as a control condition in clinical trials. A positive placebo response is seen in up to 50% of patients with Parkinson disease (PD), pain syndromes, and depression. The response is more pronounced with invasive procedures or advanced disease. Physiologic and biochemical changes have been studied in an effort to understand the mechanisms underlying placebo-related clinical improvement. In PD, objective clinical improvements in parkinsonism correlate with dopaminergic activation of the striatum, documented by PET and with changes in cell firings of the subthalamic nucleus documented by single cell recordings. Dopaminergic pathways mediating reward may underlie PL-mediated improvement in PD. In pain syndromes, endogenous opioid release triggered by cortical activation, especially the rostral anterior cingulated cortex, is associated with PL-related analgesia and can be reversed by opioid antagonists. Covert treatment of an analgesic is less effective than overt treatment, suggesting an expectation component to clinical response. In depression, PL partially imitates selective serotonin reuptake inhibitor-mediated brain activation. Diseases lacking major "top-down" or cortically based regulation may be less prone to PL-related improvement.
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PMID:The placebo treatments in neurosciences: New insights from clinical and neuroimaging studies. 1950 32

Mentalistic variables must be considered to reach a correct understanding of the neurophysiological basis of behavior in humans. Confusion regarding the relative importance of neurophysiological and mentalistic variables can lead to important misconceptions about causes and effects in the study of human behavior. In this article, we review neuroimaging studies of the effect of psychotherapy in patients suffering from diverse forms of psychopathology (obsessive-compulsive disorder, panic disorder, unipolar major depressive disorder, spider phobia). We also review neuroimaging studies of the placebo effect in healthy individuals (placebo analgesia, psychostimulant expectation) and patients with Parkinson's disease or unipolar major depressive disorder. Mental functions and processes involved in diverse forms of psychotherapy exert a significant influence on brain activity. With regard to the placebo effect, beliefs and expectations can markedly modulate neurophysiological and neurochemical activity in brain regions involved in perception, movement, pain and various aspects of emotion processing. The findings of the neuroimaging studies reviewed here strongly support the view that the subjective nature and the intentional content of mental processes significantly influence the various levels of brain functioning (e.g. molecular, cellular, neural circuit) and brain plasticity.
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PMID:Effect of mind on brain activity: evidence from neuroimaging studies of psychotherapy and placebo effect. 1902 97

Based on the observation that the placebo effect in Parkinson's disease was mediated by the release of endogenous dopamine in both the dorsal and ventral striatum, in 2002 we formally proposed the placebo-reward hypothesis. This hypothesis establishes a link between the placebo effect and reward mechanisms, and predicts that the activation of the ventral striatum should be present in any placebo response, in any medical condition. In keeping with this prediction, functional neuroimaging studies have shown placebo-induced activation of the reward circuitry in Parkinson's disease, depression, and pain. In fact, recent evidence suggests that the release of dopamine in the ventral striatum likely triggers the activation of the endogenous opioid system in placebo analgesia. The placebo-reward hypothesis also supports the notion that the expectation of clinical benefit plays a major role in the placebo effect. Probability and trust, two key factors involved in shaping expectations, must therefore be essential to the development of placebo responses. The ventral loop of the basal ganglia circuitry (anterior cingulate cortex-ventral striatum-ventral pallidum- mediodorsal nucleus of the thalamus -anterior cingulate cortex) is a fundamental component of the neuroanatomy of the placebo effect.
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PMID:The placebo-reward hypothesis: dopamine and the placebo effect. 2008 13

Placebos are useful in the medical care of the elderly, although the exact definition of a "placebo" or "placebo effect" is difficult to define precisely. They have an important role as control treatments in research trials, but a non-specific "placebo effect" may also be beneficial part of many physician-patient interactions. Physicians also give them deliberately according to several studies worldwide to satisfy patient demands or because they believe in a "placebo effect" among other reasons. A significant placebo effect has been observed among older patients in clinical trials of antidepressants (12-15%), and in treatments of Parkinson's disease (16%). Placebos activate serotonergic pathways in the brain used by antidepressants. In Parkinson's disease, the administration of a placebo stimulates dopamine release in the dorsal (resulting in motor effects) and ventral striatum (which influences expectation of reward). Much of our understanding of the placebo effect comes from studies of placebo analgesia which is influenced by conditioning, expectation, meaning and context of the treatment for the patient, and patient-physician interaction. It is anatomically medicated by brain opioid pathways. Response to "sham" acupuncture in osteoarthritis may be an example of its use in the elderly. Placebos have often been considered a deception and thus unethical. On the other hand, some physicians and ethicists have suggested conditions for appropriate uses for placebos. A placebo might offer the theoretical advantage of an inexpensive treatment that would not cause adverse drug reactions or interactions with other medications, potentially avoiding complications of polypharmacy.
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PMID:Would the elderly be better off if they were given more placebos? 2010 Feb 89

Neurobiology of the placebo effect dates back to 1978, when Levine discovered that its analgesic action is reversed by naloxone. Since then, various studies have been performed to estimate the impact of placebo on brain metabolism and neurotransmission in analgesia, depression or the Parkinson's disease. A number of involved brain structures have been pinpointed, these including nucleus accumbens and the anterior cingulate cortex (ACC), while the role ofopioid regulation has been established as significant to the process. Currently, modern diagnostic appliances such as PET or fMRI are being used to determine the differences between placebo and drug effect on brain metabolism and, consequently, to identify factors responsible for therapeutic response and their potential correlation with a psychological impact. Environmental conditions, which may result in placebo efficacy increase of seven percent per decade during the last years, are also looked into. Although certain ethical and legal dilemmas appear considering the use of placebo, it is beyond any doubt that realising the influence of expectation and conditioning on the neurobiology of the placebo effect, as well as on the proper therapy, should enable better patient handling and treatment in the future.
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PMID:[Neurobiological expression of the placebo effect]. 2067 41


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