Table 1.
Sample characteristics and main information about the methods and results of the included studies. The studies are ordered by severity of the motor impairment of the sample measured by UPDRS-III
| Characteristics of participants | Methods and results | |||||||
| Study – Country (design) | Groups, n. volunteers (Sex, n. male) | Age (Time onset of disease) Years, mean±SD | UPDRS off/UPDRS on | H&Y | LED (mg/day) (mean±SD) | Task during EEG | Analysis method | Results |
| Van den Heuvel et al., 2018 [38] – Netherlands (cross-sectional) | PD = 24(16) CG = 15(8) | PD = 67.6±8.7 (8.58±6.92) CG = 66.9±6.8 | Off = ND On = 45±16.3 | 2.0 (37.5%); 2.5 (50%); 3.0 (12.5%) | 751.1±412.0 | Rhythmic swaying movements | ERP of alpha, beta and gamma band | There was no difference in alpha, beta or gamma band, in comparison to controls. However, PD group showed significantly higher beta modulation in primary motor cortex. |
| Praamstra et al., 1998 [37] – Netherlands (cross-sectional) | PD = 7(6) CG = 7(6) | PD = 59±9 (5.43±ND) CG = 60±10 | Off = ND On = 31.0±8.0 | 2 (57.1%); 2.5 (14.3%); 3 (28.6%) | 512.5±356.8 | Index finger movement | ERP | ERP were not significantly different between groups. |
| Wascher et al., 1997 [21] – Germany (cross-sectional) | PD = 15(11) CG = 15(7) | PD = 62.2±9.8 (5.1±2.7) CG = 61.7±8.1 | Off = ND On = 23.3±17b | 1.5 (33.3%); 2 (33.3%); 2.5 (20%); 3 (13.3%) | 216.7±133.2 | Clock task and validity task | ERP | ERP were reduced during the two tasks in PD compared to CG. |
| Stegemoller et al., 2016 [18] – USA (cross-sectional) | PD = 9(5) CG = 9(5) | PD = 65.0±8.0 (ND) CG = 65.0±9.0 | Off = 31.4±7.2 On = 23.2±6.4 | ND | 1190±465 | Hand finger movement | Power spectrum analysis of alpha and beta band | At the pacing rate of 1 Hz, PD (OFF and ON) and CG showed an attenuation of power in the alpha and beta bands before movement onset and lasting the duration of the movement. The attenuation at higher pacing rates (>2 Hz) ON medication was less than OFF medication. There was not between group difference. |
| Smith et al., 2012 [35] – USA (cross-sectional) | PD = 12(11) CG = 12(6) | PD = 67.5±6.0 (6.4±4.4) CG = 62.9±7.9 | Off = ND On = 23±9.7 | 2 or 3±ND | ND | Balance task | Event related spectral (ERS) of alpha and beta band | In PD there is higher ERS of beta band in the condition of predictable perturbations of small magnitude (CZ) associated with decreased adaptability of postural responses. Preparative cortical activity may have a more direct influence on the postural response scale for people with PD than for control. |
| Gobbelé et al., 2008 [33] – Germany (cross-sectional) | PD = 12(6) CG = 12(6) | PD = 63±7.4 (5.8±0.4) CG = 61±8.3 | Off = ND On = 23±11 | 2.5±0.4 | ND | Resting | SEP | Low frequency and high oscillation signals showed no significant differences between PD patients and the control group. |
| Stemmer et al., 2007 [19] – Canada (cross-sectional) | PDoff = 9(6) PDon = 9 (4) CG = 14 (5) | PDon = 64.2±11.5 (ND) PDoff = 63.4±20.7 (ND) CG = 65.6±20.0 | Off = 21.3±ND On = 22.7±ND | PDon =2.1±ND PDoff = 2.6±ND | ND | Index finger movement | ERP | ERP of PD patients (OFF and ON) are similar to each other but both are reduced at frontal sites compared to CG. |
| Beudel et al., 2015 [30] – Nehterlands (cross-sectional) | PD = 24 (13) CG = 10(6) | PD = 64.2±1.8 (6.6±1.1) CG = 65.2±3.2 | Off = 21.0±2.8 On = ND | ND | ND | Resting | Average peak frequency of alpha band | Average peak frequency in bradykinetic PD was significantly slower than in control. |
| Stanzione et al., 1996 [32] – Italy (cross-sectional) | PD = 19(7) CG = 22(ND) | PD = 63.5±7.6 (ND) CG = 63±8.2 | Off = ND On = 18.5±7.1b | 1.0 (5,6%) 1.5 (11,2%) 2.0 (22,3%) 2.5 (39,1%) 3.0 (21,6%) | ND | Resting | Power spectrum analysis of delta; theta; alpha and beta band | The mean delta power was higher in the PD CG, just as the mean beta power was lower in PD patients. Other bands did not show significant differences between groups. |
| Emek-Savas et al., 2017 [28] – Turkey (cross-sectional) | PD = 16(13) CG = 16(13) | PD = 66.8±7.9 (3.7±2.9) CG = 68.9±5.9 | Off = ND On = 17±8.6 | 2.2±0.8 | ND | Resting | ERP of delta band | ERP were significantly lower for patients with PD than for healthy controls (Cz and C4). |
| Macerollo et al., 2016 [17] – England (cross-sectional) | PD = 18(9) CG = 16(8) | PD = 62±34.6 (4.2±2.4) CG = 58±20.4 | Off = 11.8±3.7 On = 6.7±2.4 | ND | ND | Resting | SEP | SEP did not attenuate in PD patients OFF, presented when ON medication. The difference in SEP attenuation was reduced in PD patients OFF compared with ON medication. |
| Degardin et al., 2009 [16] – France (crossover) | PD = 13(9) CG = 12(5) | PD = ND (ND) CG = ND | Off = ND On = ND | ND | 381.0±ND | Passive and active movement of hand fingers | ERP of beta band | ERP was more intense in CG than in PD patients OFF (after both active and passive movement). There were no significant inter-groups and inter-condition differences in the latency of the ERP over the contralateral sensorimotor area. The number of electrodes presenting ERP over the sensorimotor area in PD patients OFF medication is lower than in CG (after both active and passive movement). |
| Liu et al., 2017 [29] – China (cross-sectional) | PD = 17(7) CG = 25(18) | PD = ND (ND) CG = ND | Off = ND On = ND | ND | ND | Resting | Power spectrum analysis | It was found that there is power spectrum difference between groups in O2; however, it was not made statistical analysis. |
| Magnani et al., 1998 [34] – Italy (cross-sectional) | PD = 10(2) CG = 10(6) | PD = 63.8±9.5 (4.9±2.1) CG = 60.4±8.4 | Off = ND On = ND | 2.3±0.4 | 410±194.9 | Index finger movement | ERP of alpha band | The topographic distribution of ERP was different between groups: in CG, ERP was greatest on the parietal areas contralateral to the movement, in PD group ERP was localized more anteriorly, on the central regions contralateral to the movement (C3 and C4). |
| Neufeld et al., 1994 [27] – Israel (cross-sectional) | PD = 20(6) CG = 10(3) | PD = 72.3±6.0 (5.8±3.3) CG = 72.7±5.6 | Off = ND On = ND | 1 (10%) 2 (30%) 3 (50%) 4 (10%) | ND | Resting | Power spectrum analysis of delta; theta; alpha and beta band. | The alpha amplitude was significantly decreased in PD patients, unrelated to motor disability. There was a non-significant increased amplitude in delta and theta range in the demented PD patients as compared to nondemented PD and CG. |
| Serizawa et al., 2008 [39] – Japan (cross-sectional) | PD = 45(22) CG = 40(14) | PD = 71.4±44.5 (5.7±25.7) CG = 69.2±35.5 | Off = ND On = ND | 1 (2.2%); 2 (37.8%); 3 (48.9%); 4 (11.1%) | ND | Resting | Power spectrum analysis of delta; theta; alpha and beta band | The ratios in the slow waves against the total power value in the PD were higher. Total power spectrum of fast waves was lower than in CG, at all electrode locations. |
| Swann et al., 2015 [20] – USA (cross-sectional) | PD = 15(7) CG = 16(7) | PD = 63.2±8.2 (4.5±3.5) CG = 63.5±9.6 | Off = ND On = ND | 2 or 3±ND | ND | Resting | Power spectral analysis of beta band and gamma band | There was no difference in beta or gamma power in comparison to controls. |
| Tamás et al., 2003 [36] – Hungary (cross-sectional) | PD = 10(5) CG = 8(4) | PD = 60.9±13.7 (4.8±3.8) CG = 61.1±9.6 | Off = ND On = ND | 1 (20%); 1.5 (20%); 2 (30%); 2.5 (30%) | 267.5±68.8a | Finger movement | ERP of beta band | ERP was lower in the contralateral hemisphere when patients moved their tremulous hand, the ERP did not differ significantly in the ipsilateral hemisphere. There were not intergroup differences. |
| Touge et al., 1995 [31] – UK (cross-sectional) | PD = 8(6) CG = 8(2) | PD = 56.5±26.7 (7.3±3.9) CG = 63.9±26.7 | Off = ND On = ND | 2 (50%); 3 (50%) | 369.3±150.6 | Movement of the arm | ERP | In CG ERP was higher prior to random-choice task in comparison to repetitive task. This difference was not founded in PD group. There was not difference between groups for ERP amplitude prior to repetitive task. ERP were reduced during the two tasks in PD compared to CG (all electrodes, except for F4). |
aLevodopa equivalent conversion; bwhen the study did not specified the state of UPDRS assessment we considered the value at ON state; CG, control group; ERP, event related potential; ERS, event related spectral analysis; Hz, hertz; LED, Levodopa equivalent dosage; mg, milligram; ND, not described; PD, Parkinson’s disease; SD, standard deviation; SEP, somatosensory evoked potential; UK, United Kingdom; USA, United States of America.