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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