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13 results

  • Chapter 6 - Functional MRI of cognition and mood in Parkinson’s disease

  • Edited by Paul Tuite, University of Minnesota, Alain Dagher
  • Book:
    Magnetic Resonance Imaging in Movement Disorders
    Published online:
    05 October 2013
    Print publication:
    10 October 2013, pp 72-83

  • Summary

    Parkinson's disease (PD) is associated with cognitive and emotional disturbances, whose response to dopamine therapy is either absent or, occasionally, deleterious to the patient. By measuring cerebral blood flow (CBF), first with positron emission tomography (PET) and now with functional magnetic resonance imaging (fMRI), researchers have mapped the neurobiological substrates of cognitive and behavioral symptoms in PD. Basal ganglia processing is based on the anatomy of parallel cortico-striatal loops, each of which has a functional role. Dopaminergic overmedication may lead to cognitive impairment via an action on the relatively preserved mesocortical or mesolimbic systems. The overmedication hypothesis has been rekindled recently with the description of disorders of motivation and impulse control in PD. fMRI provides evidence that dopamine may contribute to impulse control disorders (ICDs) in PD via its role as an energizing or activating agent that assigns incentive value to stimuli and actions.

Magnetic Resonance Imaging in Movement Disorders
  • A Guide for Clinicians and Scientists
  • Edited by Paul Tuite, Alain Dagher
  • Published online:
    05 October 2013
    Print publication:
    10 October 2013
  • Magnetic Resonance Imaging in Movement Disorders is the first book to focus in detail on MRI in a range of movement disorders. Since MRI was first employed in imaging Parkinson's disease, the number of imaging techniques and their application in diagnosis and management has extended widely. The book shows various imaging strategies ranging from functional, structural and chemical methods as they relate to both motor and non-motor aspects of Parkinson's disease and other conditions such as Huntington's disease and dystonia. Chapters on MRI in surgery and using MRI as a potential outcome measure in clinical trials show the clinical relevance of methods. Novel methods including DTI, tractography and resting case studies are described in detail. The book also summarises the relevance of fMRI to various aspects of movement disorders. Magnetic Resonance Imaging in Movement Disorders is essential reading for neurologists, radiologists and movement disorder specialists.

  • Dissecting the Effects of Disease and Treatment on Impulsivity in Parkinson's Disease

  • Alison C. Simioni, Alain Dagher, Lesley K. Fellows
  • Journal:
    Journal of the International Neuropsychological Society / Volume 18 / Issue 6 / November 2012
    Published online by Cambridge University Press:
    19 October 2012, pp. 942-951

  • Converging evidence, including observations in patients with Parkinson's disease (PD), suggests that dopamine plays a role in impulsivity. This multi-faceted construct includes considerations of both time and risk; determining how these more specific processes are affected by PD and dopaminergic treatment can inform neurobiological models. We examined the effects of PD and its treatment on temporal discounting and risky decision-making in a cohort of 23 mild-moderate PD patients and 20 healthy participants. Patients completed the Balloon Analogue Risk Task and a temporal discounting paradigm both on and off their usual dopamine replacement therapy. PD patients did not differ from controls in their initial risk-taking on the Balloon Analogue Risk Task, but took progressively more risks across trials when on medication. A subset of patients and controls was tested again, 1.5–3 years later, to explore the effects of disease progression. On follow-up, baseline risk-taking diminished in patients, but the tendency to take increasing risks across trials persisted. Neither disease progression nor its treatment affected the temporal discounting rate. These findings suggest a different neural basis for temporal discounting and risk-taking, and demonstrate that risk-taking can be further decomposed into initial and trial-by-trial effects, with dopamine affecting only the latter. (JINS, 2012, 18, 1–10)

  • Effects of lowered serotonin transmission on cocaine-induced striatal dopamine response: PET [11C]raclopride study in humans

  • Sylvia M. L. Cox, Chawki Benkelfat, Alain Dagher, J. Scott Delaney, France Durand, Theodore Kolivakis, Kevin F. Casey, Marco Leyton
  • Journal:
    The British Journal of Psychiatry / Volume 199 / Issue 5 / November 2011
    Published online by Cambridge University Press:
    02 January 2018, pp. 391-397
    Print publication:
    November 2011
    • Article
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  • Background

    Low serotonin transmission is thought to increase susceptibility to a wide range of substance use disorders and impulsive traits.

    Aims

    To investigate the effects of lowered serotonin on cocaine-induced (1.0 mg/kg cocaine, self-administered intranasally) dopamine responses and drug craving.

    Method

    In non-dependent cocaine users, serotonin transmission was reduced using the acute tryptophan depletion method. Striatal dopamine responses were measured using positron emission tomography with [11C]raclopride.

    Results

    Acute tryptophan depletion increased drug craving and striatal dopamine responses to cocaine. These acute tryptophan depletion-induced increases did not occur in the absence of cocaine.

    Conclusions

    The results suggest that low serotonin transmission can increase dopaminergic and appetitive responses to cocaine. These findings might identify a mechanism by which individuals with low serotonin are at elevated risk for both substance use disorders and comorbid conditions.