Int Rev Neurobiol
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Parkinson's disease (PD) is a neurodegenerative disease characterized by the degeneration of dopaminergic nigrostriatal connections which is recognized as the major pathophysiological event underlying the onset of motor symptoms. Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT) imaging allow the study of these connections in vivo at a molecular level. ⋯ PET molecular imaging could be a reliable biomarker to aid earlier diagnosis and for monitoring disease progression. Furthermore, PET imaging could be used as outcome measure in the design of clinical trials testing novel pharmacological compounds aiming to slow, and ultimately halt, disease progression.
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There is strong behavioral evidence that placebo and nocebo effects can influence aspects of motor performance like speed, force, and resistance to fatigue in athletes and non-athletes alike. These behavioral studies were essential for extending experimental investigation of the placebo and nocebo effects from the pain to the motor domain and to reveal how verbal suggestions and experiential learning are involved in shaping modulatory systems and related behavioral responses. ⋯ Further evidence derives from studies in patients with Parkinson's disease that have directly demonstrated that placebo-induced improvements in motor symptoms are related to changes in subcortical neural firing activity and dopamine release. Future investigations are needed to better clarify the complex neural architecture underpinning the placebo and nocebo effects in the motor domain.
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Learning is a key mechanism underpinning the development of the nocebo effect. The learning literature has cataloged and explored numerous ways in which the environment can be manipulated to prevent, reduce, or eradicate learning. ⋯ These learning strategies include overshadowing, latent inhibition, extinction, and contingency degradation. These strategies represent important new avenues for investigation and should be used by researchers to design and test interventions to reduce nocebo effects.