Neural substrates of impulse control: Insights from neurodegenerative disease
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1
Neuroscience Research Australia, Australia
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2
University of New South Wales, School of Medical Sciences, Australia
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3
Brain and Mind Research Institute, University of Sydney, Australia
Background: Impulsivity is not a unitary construct, but rather is comprised of several different forms that are underpinned by distinct anatomical substrates. In particular, ‘waiting’ impulsivity – the ability to delay gratification – has been associated with fronto-subcortical limbic circuitry in animal models and via functional imaging approaches in psychiatric disorders. Impulsivity can also emerge in neurodegenerative conditions that show grey matter atrophy in impulse control circuitry, for example frontotemporal dementia (FTD) and Parkinson’s disease (PD). As such, these conditions provide a ‘lesion model’ approach that can further define the neural substrates of impulse control in humans.
Methods: Twenty-one FTD and twenty-two PD patients, with eighteen Controls, were assessed on a delay discounting task and underwent a battery of standard executive function measures. Voxel-based morphometry (VBM) analysis was used to determine the relationship between impulsivity and regional grey matter atrophy.
Results: Behaviourally, FTD patients demonstrated significant impulsivity on the delay discounting task; task performance was also a more sensitive diagnostic marker for FTD when compared to traditional executive tests. Imaging analysis in the patient groups revealed that specific fronto-subcortical regions (ventrolateral striatum, amygdala, anterior cingulate cortex) covaried with impulsivity on the task.
Discussion: This study is the first to show common neuroanatomy underpinning ‘waiting’ impulsivity in neurodegenerative populations. Importantly, the findings converge with the ‘waiting’ circuitry previously defined in the preclinical literature and in psychiatric disorders, and further confirm that this form of impulsivity is underpinned by specific limbic regions involved in the brain’s reward system. Clinically, these results have important implications for neurodegenerative conditions – particularly FTD – where impulsive behaviour has typically been related to orbitofrontal damage. Our results suggest that atrophy in subcortical limbic regions also crucially mediates ‘waiting’ impulsivity, which will inform the development of future therapeutic targets for impulse control deficits in both FTD and PD.
Keywords:
impulsivity,
reward system,
Neuropsychology,
Human lesion model,
MRI imaging,
Neurodegenerative Diseases
Conference:
ACNS-2013 Australasian Cognitive Neuroscience Society Conference, Clayton, Melbourne, Australia, 28 Nov - 1 Dec, 2013.
Presentation Type:
Poster
Topic:
Executive Processes
Citation:
O'Callaghan
C,
Shine
JM,
Hodges
JR,
Lewis
SJ and
Hornberger
M
(2013). Neural substrates of impulse control: Insights from neurodegenerative disease.
Conference Abstract:
ACNS-2013 Australasian Cognitive Neuroscience Society Conference.
doi: 10.3389/conf.fnhum.2013.212.00076
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Received:
15 Oct 2013;
Published Online:
25 Nov 2013.
*
Correspondence:
Ms. Claire O'Callaghan, Neuroscience Research Australia, Sydney, Australia, claire.ocallaghan@sydney.edu.au