Abstract
Attention dysfunction is a common but often undiagnosed cognitive impairment in Parkinson's disease that significantly reduces quality of life. We sought to increase understanding of the mechanisms underlying attention dysfunction using functional neuroimaging. Functional MRI was acquired at two repeated sessions in the resting state and during the Attention Network Test, for 25 non-demented subjects with Parkinson's disease and 21 healthy controls. Behavioral and MRI contrasts were calculated for alerting, orienting, and executive control components of attention. Brain regions showing group differences in attention processing were used as seeds in a functional connectivity analysis of a separate resting state run. Parkinson's disease subjects showed more activation during increased executive challenge in four regions of the dorsal attention and frontoparietal networks, namely right frontal eye field, left and right intraparietal sulcus, and precuneus. In three regions we saw reduced resting state connectivity to the default mode network. Further, whereas higher task activation in the right intraparietal sulcus correlated with reduced resting state connectivity between right intraparietal sulcus and the precuneus in healthy controls, this relationship was absent in Parkinson's disease subjects. Our results suggest that a weakened interaction between the default mode and task positive networks might alter the way in which the executive response is processed in PD.
Highlights
Attention dysfunction is commonly present in people with Parkinson's disease (PD) without dementia (Aarsland et al, 2010), and bears a significant impact on quality of life, with subjects finding difficulty maintaining concentration (Barone et al, 2009), and increasing evidence suggesting a role of attention dysfunction in falls and gait disturbance (Amboni et al, 2013)
A significant effect was observed for alerting, F(1,42) = 7.15, p b 0.05, but not orienting, F(1,42) ≤ 0, ns
RIPS showed reduced resting state functional connectivity (rsFC) to the default mode network (DMN) in 100% of subjects. Both PD and healthy controls (HC) engaged a set of regions known to be activated in goal-directed tasks (Cabeza and Nyberg, 2000; Duncan, 2010)
Summary
Attention dysfunction is commonly present in people with Parkinson's disease (PD) without dementia (Aarsland et al, 2010), and bears a significant impact on quality of life, with subjects finding difficulty maintaining concentration (Barone et al, 2009), and increasing evidence suggesting a role of attention dysfunction in falls and gait disturbance (Amboni et al, 2013). Work suggested behavioral deficits only manifest when task demands exceed attention resources in the frontal cortex under novel, non-routine conditions (Stam et al, 1993), or for tasks that depend on internal cues (Brown and Marsden, 1988). PET imaging studies in PD demonstrate glucose hypometabolism in frontal and parietal areas and imply an important component of cortical dysfunction (Klein et al, 2010; Meles et al, 2015), which is further supported by findings of cortical thinning in PD (Madhyastha et al, 2015b). More recent work suggests that degeneration of the ascending cholinergic system might impair attention networks in PD (Sarter et al, 2014)
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