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Table 1 Summary of the characteristics of the reviewed studies

From: The study of brain functional connectivity in Parkinson’s disease

Paper

Number of patients

Task

Type of connectivity

Main findings

Wu T et al., 2011 [12]

18 PD patients

A self-initiated right hand tapping task

Effective connectivity

psychophysiological interaction (PPI)

The striatum-cortical connections were weakened, while the cortico-cerebellar connections were strengthened in PD

18 controls

Rowe J et al., 2002 [13]

12 PD patients

An overlearned motor sequence task, with and without attention

Effective connectivity

• Structural equation modeling (SEM)

Attention to action did not increase the connectivity between the prefrontal cortex, lateral premotor cortex and SMA in PD

12 controls

Wu T et al., 2010 [14]

12 patients

two sequences of right hand finger tapping

Effective connectivity

psychophysiological interaction (PPI)

The pre-SMA, cerebellum, and cingulate motor area had increased effective connectivity with brain networks in PD

12 age-and sex-matched healthy subjects

Rowe JB et al., 2010 [15]

16 PD patients

A visually paced finger-tapping task

Effective connectivity

Dynamic causal modelling (DCM)

The coupling between the prefrontal cortex and the pre-SMA was enhanced in PD

42 controls

Wu T et al., 2016 [27]

36 PD patients

Handwriting

Functional connectivity

Dysfunction of basal ganglia motor circuit in both consistent and progressive. Progressive micrographia was also associated with disconnections between the pre-SMA, rostral cingulated motor area and cerebellum

18 controls

Wu T et al., 2015 [22, 29]

22 PD patients

Visuomotor association task

Effective connectivity

Granger causality analysis (GCA)

The connectivity from the putamen to the motor cortex was decreased in PD

22 controls

Ma H et al., 2015 [30]

50 PD patients

Resting state

Functional connectivity

The bilateral dentate nucleus had higher connectivity with the bilateral cerebellar anterior lobe, and lower connectivity with the bilateral prefrontal cortex in tremor-dominant PD

29 age-matched health controls

Tessitore A et al., 2012 [32]

29 PD patients

Resting state

Functional connectivity

Reduced connectivity within both executive-attention and visual networks

15 controls

Liu H et al., 2013 [34]

9 PD patients

Resting state

Functional connectivity

Decreased connectivity of the dentate nucleus with the bilateral cerebellar posterior lobe in tremor-dominant PD

9 controls

Hu X et al., 2015 [35, 43]

21 tremor-dominant (TD)-PD

Resting state

Voxel-mirrored homotopic connectivity (VMHC)

TD-PD exhibited significantly lower VMHC values in the posterior lobe of the cerebellum. AR-PD exhibited lower VMHC values in the precentral gyrus.

29 akinetic-rigid (AR)-PD patients

26 controls

Seibert TM et al., 2012 [36]

19 cognitively unimpaired controls, 19 cognitively unimpaired PD patients,

Resting state

Functional connectivity

Decreased striato-prefrontal connectivity in patients with dementia

18 patients with dementia

Gorges M et al., 2015 [37]

14 cognitively unimpaired PD patients, 17 cognitively impaired PD patients

Resting state

Functional connectivity

Decreased default mode network connectivity in cognitively impaired PD patients.

22 controls

Disbrow EA et al., 2014 [38]

14 non-demented PD patients, 20 controls.

Resting state

Functional connectivity

Decreased default mode network connectivity in PD

Manza P et al., 2016 [41]

62 early-stage PD patients

Resting state

Functional connectivity

Motor deficit was associated with weaker coupling between anterior putamen and midbrain, cognitive impairment was associated with stronger coupling between the dorsal caudate and the rostral anterior cingulate cortex

Luo C et al., 2014 [42]

29 PD patients with depression, 30 PD patients without depression, 30 controls

Resting state

Functional connectivity

Reduced connectivity in the prefrontal-limbic network in the depression group

Hu X et al., 2015 [35, 43]

20 depressed PD patients, 40 non-depressed PD patients, 43 controls

Resting state

Functional connectivity

Stronger connectivity between the left median cingulate cortex and default mode network in the depressed PD

Sunwoo MK et al., 2015 [46]

110 PD patients subdivided into three groups based on olfactory performance

Resting state

Functional connectivity

Enhancement of striatocortical connectivity in the bilateral occipital areas and right frontal areas in patients with olfactory impairment

Baggio HC et al., 2015 [47]

62 PD patients, 31 controls

Resting state

Functional connectivity

Reduced connectivity in left-sided circuits, predominantly involving limbic, striatal and frontal territories in apathetic PD patients

Yao N et al., 2015 [48]

12 PD patients without hallucinations, 12 PD patients with visual hallucinations, 14 controls

Resting state

Functional connectivity

Increased occipital-corticostriatal connectivity in PD patients with visual hallucinations

Kwak Y et al., 2010 [50]

24 mild to moderate stage PD patients, 24 controls

Resting state

Functional connectivity

Increased cortico-striatal connectivity in PD patients

Agosta F et al., 2014 [51]

69 PD patients, 25 drug-naïve, 44 dopamine treated, 27 controls

Resting state

Functional connectivity

Decreased striato-thalamic connectivity, increased striato-temporal, and thalamo-cortical connections in dopaminergic treated PD

Bell PT et al., 2015 [52]

39 PD patients, controls

Resting state

Functional connectivity

Decoupling between the striatum and thalamic and sensorimotor networks in PD

Szewczyk-Krolikowski K et al., 2014 [53]

19 PD patients, 19 controls

Resting state

Functional connectivity

Reduced basal ganglia network connectivity in PD

Herz DM et al., 2015 [54]

26 PD patients

Visually cued movement

Effective connectivity

Dynamic causal modelling (DCM)

Increase in the putamen and primary motor cortex connectivity after levodopa intake during movement suppression in patients who later developed levodopa-induced dyskinesias

Herz DM et al., 2016 [55]

12 PD patients with dyskinesias, 12 patients without dyskinesias

Resting state

Functional connectivity

Increased connectivity between the primary sensorimotor cortex and putamen after levodopa intake in patients with dyskinesias

Kahan J et al., 2014 [57]

12 PD patients

Resting state

Effective connectivity

Dynamic causal modelling (DCM)

The strength of effective subthalamic nucleus afferents and efferents were reducedm cortico-striatal, thalamo-cortical and direct pathways were strengthened by DBS

Schweder PM et al., 2010 [58]

1 PD patient

Resting state

Functional connectivity

Normalization of pathological pedunculopontine nucleus (PPN) connectivity after PPN-DBS

Long D et al., 2012 [59]

19 early PD patients, 27 controls

Resting state

RFCS (regional functional connectivity strength)

The PD patients showed significant RFCS increases in the left parahippocampal gyrus, left angular gyrus and right middle temporal gyrus