Table 2.
Inventory of non-significant correlations between STN-LFP signal features and UPDRS symptom severity
| Study | n Patients/Hemispheres | LFP signal feature | UPDRS items | Medication state | Outcomea |
|---|---|---|---|---|---|
| Beta-based | |||||
| Kühn et al. (2006) [13] | 9/17 | Absolute spectral power within ± 2.5 Hz range around peak (8–35 Hz) | Hemibody tremor | Levodopa-induced changes |
ρ = 0.25 p = 0.54 |
| Marceglia et al. (2006) [62] | 21/21 | Absolute spectral power (13–20 Hz)b | Total UPDRS-III | Off |
R2 = 0.10 p = 0.14 |
| Ray et al. (2008) [51] | 5/9 | Absolute spectral peak power (8–35 Hz) | Hemibody bradykinesia + rigidity | Off |
ρ = –0.35 p = 0.15 |
| 5/9 | Absolute spectral peak power (8–35 Hz) | Hemibody tremor | Levodopa-induced changes |
ρ = –0.30 p = 0.15 |
|
| Kühn et al. (2009) [14] | 30/51 | Absolute spectral power within ± 5.5 Hz range around peak (8–35 Hz) | Hemibody tremor | Levodopa-induced changes |
R2 = 0.00 p = 0.99 |
| Chen et al. (2010) [26] | 12/23 | Lempel-Ziv complexity 13–35 Hz | Hemibody tremor | Off |
ρ = –0.22 p = 0.31 |
| 12/23 | Absolute spectral power (13–35 Hz) | Hemibody tremor | Off | ρ = 0.48 | |
| 12/23 | Normalised spectral power (13–35 Hz) | Hemibody tremor | Off | ρ = 0.51 | |
| Pogosyan et al. (2010) [23] | 18/36 | Phase coherence between unilateral contacts (13–35 Hz) | Hemibody tremor | Off | R2 = 0.00 |
| López-Azcárate et al. (2010) [15] | 14/26 | Normalised spectral peak power (12–20 Hz) | Hemibody tremor | Off | |
| Little et al. (2012) [27] | 18/36 | Coefficient of variation spectral power over time (21–33 Hz) | Hemibody tremor | Off |
ρ = –0.24 p = 0.16 |
| 10/17 | Coefficient of variation spectral power over time (21–33 Hz) | Hemibody tremor | Levodopa-induced changes |
ρ = 0.14 p = 0.60 |
|
| Hohlefeld et al. (2013) [52] | 10/10 | Imaginary part of coherency between unilateral contacts (10–30 Hz)b | Total UPDRS-III | Off | |
| 10/19 | Imaginary part of coherency between unilateral contacts (10–30 Hz)b | Total UPDRS-III | On | ||
| Hohlefeld et al. (2014) [53] | 8/8 | Coherence between bilateral contacts (10–20 Hz)b | Total UPDRS-III | Off |
R2 = 0.00 p = 1.00 |
| 8/8 | Coherence between bilateral contacts (10–20 Hz)b | Total UPDRS-III | On | ||
| 8/8 | Coherence between bilateral contacts (10–20 Hz)b | Total UPDRS-III | Levodopa-induced changes | ||
| 8/8 | Imaginary part of coherency between bilateral contacts (10–20 Hz)b | Total UPDRS-III | On | ||
| 8/8 | Imaginary part of coherency between bilateral contacts (10–20 Hz)b | Total UPDRS-III | Levodopa-induced changes | ||
| van Wijk et al. (2016) [18] | 19/38 | Normalised spectral power (13–20 Hz) | Hemibody bradykinesia + rigidity | Levodopa-induced changes |
R2 = 0.08 p = 0.09 |
| West et al. (2016) [21] | 12/23 | Coherence between unilateral contacts (13–20 Hz) | Hemibody bradykinesia + rigidity | Levodopa-induced changes |
R2 = 0.09 ρ = 0.40 p = 0.06 |
| 11/11 | Coherence between bilateral contacts (13–20 Hz)b | Bradykinesia + rigidity | Off |
R2 = 0.23 ρ = 0.42 p = 0.21 |
|
| 12/12 | Coherence between bilateral contacts (13–20 Hz)b | Bradykinesia + rigidity | Levodopa-induced changes |
R2 = 0.06 ρ = 0.13 p = 0.68 |
|
| 12/24 | Weighted phase lag index between unilateral contacts (13–20 Hz) | Hemibody bradykinesia + rigidity | Levodopa-induced changes |
R2 = 0.11 ρ = 0.27 p = 0.20 |
|
| 11/11 | Weighted phase lag index between bilateral contacts (13–20 Hz)b | Bradykinesia + rigidity | Off |
R2 = 0.13 ρ = 0.34 p = 0.30 |
|
| 9/9 | Weighted phase lag index between bilateral contacts (13–20 Hz)b | Bradykinesia + rigidity | Levodopa-induced changes |
R2 = 0.08 ρ = 0.13 p = 0.74 |
|
| 12/21 | Detrended fluctuation analysis of phase synchrony between unilateral contacts (13–20 Hz) | Hemibody bradykinesia + rigidity | Off |
R2 = 0.04 ρ = 0.04 p = 0.85 |
|
| 12/17 | Detrended fluctuation analysis of phase synchrony between unilateral contacts (13–20 Hz) | Hemibody bradykinesia + rigidity | Levodopa-induced changes |
R2 = 0.10 ρ = –0.20 p = 0.45 |
|
| Beudel et al. (2017) [47] | 39/39 | Normalised spectral power (8–35 Hz)b | Total UPDRS-III | Off |
ρ = 0.28 p = 0.07 |
| 39/78 | Normalised spectral (peak) power (8–35 Hz) | Hemibody tremor | Off | ||
| Neumann et al. (2017) [20] | 12/24 | Normalised spectral power within ± 3 Hz range around peak (13–35 Hz) | Total hemibody | Levodopa-induced changes | |
| Martin et al. (2018) [54] | 13/26 | Normalised spectral peak power (13–35 Hz) | Hemibody tremor | Off |
ρ = –0.07 p = 0.74 |
| 13/26 | Absolute spectral peak power (13–35 Hz) | Total hemibody | Off | ρ = –0.14 | |
| 13/26 | Absolute spectral peak power (13–35 Hz) | Hemibody bradykinesia + rigidity | Off | ρ = 0.38 | |
| 13/26 | Absolute spectral peak power (13–35 Hz) | Hemibody tremor | Off | ρ = 0.28 | |
| Ozturk et al. (2020) [59] | 9/9 | Normalised spectral power (13–22 Hz) | Total hemibody | Levodopa-induced changes |
R2 = 0.06 p = 0.20 |
| 9/9 | Normalised spectral power (13–22 Hz) | Hemibody bradykinesia + rigidity | Levodopa-induced changes |
R2 = 0.16 p = 0.06 |
|
| 9/9 | Normalised spectral power (13–22 Hz) | Hemibody tremor | Levodopa-induced changes |
R2 = 0.04 p = 0.75 |
|
| Özkurt et al. (2020) [17] | 14/26 | Nonlinearity of time series (13–30 Hz) | Hemibody bradykinesia + rigidity | Off |
R2 = 0.05 p = 0.36 |
| Tamir et al. (2020) [22] | 8/12 | Normalised spectral power (13–30 Hz) | Hemibody tremor | Off |
R2 = 0.00 p = 0.88 |
| Eisinger et al. (2020) [63] | 15/19 | Absolute spectral peak power (12–30 Hz) | Total hemibody | Off |
R2 = 0.00 p = 0.83 |
| 15/19 | Absolute spectral peak power (12–30 Hz) | Hemibody bradykinesia + rigidityc | Off | R2 = 0.01 | |
| 15/19 | Absolute spectral peak power (12–30 Hz) | Hemibody tremor | Off |
R2 = 0.00 p = 0.91 |
|
| 15/19 | Amplitude of movement-related power decrease (12–30 Hz) | Total hemibody | Off |
R2 = 0.08 p = 0.25 |
|
| 15/19 | Amplitude of movement-related power decrease (12–30 Hz) | Hemibody bradykinesia + rigidityc | Off | R2 = 0.02 | |
| 15/19 | Amplitude of movement-related power decrease (12–30 Hz) | Hemibody tremor | Off |
R2 = 0.08 p = 0.24 |
|
| 15/19 | Beta burst duration | Hemibody bradykinesia/rigidity | Off | R2 = 0.00 | |
| 15/19 | Beta burst amplitude | Hemibody bradykinesia/rigidity | Off | R2 = 0.00 | |
| Telkes et al. (2020) [64] | 7/8 | Normalised spectral power (13–20 Hz) | Bradykinesia/rigidity | Off |
ρ = 0.66 p = 0.09 |
| 7/8 | Normalised spectral power (13–20 Hz) | Tremor | Off |
ρ = 0.75 p = 0.11 |
|
| Other | |||||
| Kühn et al. (2006) [13] | ?/7 | Absolute spectral power within ± 2.5 Hz range around peak (60–90 Hz) | Total hemibody | Levodopa-induced changes |
ρ = –0.64 p = 0.12 |
| Marceglia et al. (2006) [62] | 21/21 | Absolute spectral power (8–12 Hz)b | Total UPDRS-III | Off |
R2 = 0.04 p = 0.36 |
| 13/13 | Absolute spectral power (60–90 Hz)b | Total UPDRS-III | On |
R2 = 0.01 p = 0.64 |
|
| 13/13 | Absolute spectral power (260–340 Hz)b | Total UPDRS-III | On |
R2 = 0.10 p = 0.28 |
|
| Chen et al. (2010) [26] | 12/23 | Lempel-Ziv complexity 0–12 Hz | Hemibody bradykinesia + rigidity | Off |
ρ = 0.07 p = 0.76 |
| 12/23 | Lempel-Ziv complexity 0–12 Hz | Hemibody tremor | Off |
ρ = 0.07 p = 0.76 |
|
| López-Azcárate et al. (2010) [15] | 14/22 | Movement-related changes in phase-amplitude coupling (10–30 vs 200–400 Hz) | Hemibody bradykinesia + rigidity | Off |
ρ = 0.18 p = 0.60 |
| 14/26 | Normalised spectral peak power (250–350 Hz) | Hemibody tremor | Off | ||
| 14/26 | Movement-related changes in spectral peak power (250–350 Hz) | Hemibody tremor | Off | ||
| 14/26 | Phase-amplitude coupling (10–30 vs 200–400 Hz) | Hemibody tremor | Off | ||
| 14/26 | Movement-related changes in phase-amplitude coupling (10–30 vs 200–400 Hz) | Hemibody tremor | Off | ||
| Giannicola et al. (2013) [57] | 18/18 | Normalised spectral power (2–7 Hz) | Total UPDRS-III | Off |
R2 = 0.13 p = 0.13 |
| van Wijk et al. (2016) [18] | 33/65 | Normalised spectral power (150–400 Hz) | Hemibody bradykinesia + rigidity | On, off |
R2 = 0.00 p = 0.56 |
| 19/38 | Normalised spectral power (150–400 Hz) | Hemibody bradykinesia + rigidity | Levodopa-induced changes |
R2 = 0.01 p = 0.51 |
|
| 19/38 | Phase-amplitude coupling (13–20 vs 150–400 Hz) | Hemibody bradykinesia + rigidity | Levodopa-induced changes |
R2 = 0.10 p = 0.06 |
|
| West et al. (2016) [21] | 12/22 | Absolute spectral power (5–12 Hz) | Hemibody bradykinesia + rigidity | Levodopa-induced changes |
R2 = 0.08 ρ = –0.19 p = 0.39 |
| Martin et al. (2018) [54] | 13/26 | 1/f slope | Total hemibody | Off | ρ = 0.04 |
| 13/26 | 1/f slope | Hemibody bradykinesia + rigidity | Off | ρ = 0.02 | |
| 13/26 | 1/f slope | Hemibody tremor | Off | ρ = 0.08 | |
| Ozturk et al. (2020) [59] | 9/9 | Normalised spectral power (4–12 Hz) | Hemibody tremor | Levodopa-induced changes |
R2 = 0.05 p = 0.08 |
| 9/9 | Normalised spectral power (70–90 Hz) | Total hemibody | Levodopa-induced changes |
R2 = 0.03 p = 0.35 |
|
| 9/9 | Normalised spectral power (70–90 Hz) | Hemibody bradykinesia + rigidity | Levodopa-induced changes |
R2 = 0.14 p = 0.12 |
|
| 9/9 | Normalised spectral power (70–90 Hz) | Hemibody tremor | Levodopa-induced changes |
R2 = 0.11 p = 0.17 |
|
| 9/9 | Normalised spectral power (200–400 Hz) | Total hemibody | Levodopa-induced changes | ||
| 9/9 | Normalised spectral power (200–400 Hz) | Hemibody bradykinesia + rigidity | Levodopa-induced changes | ||
| 9/9 | Normalised spectral power (200–400 Hz) | Hemibody tremor | Levodopa-induced changes | ||
| 9/9 | Ratio of normalised spectral power between slow (200–300 Hz) and fast bands (300–400 Hz) | Total hemibody | Levodopa-induced changes |
R2 = 0.10 p = 0.08 |
|
| 9/9 | Ratio of normalised spectral power between slow (200–300 Hz) and fast bands (300–400 Hz) | Hemibody bradykinesia + rigidity | Levodopa-induced changes |
R2 = 0.14 p = 0.06 |
|
| 9/9 | Ratio of normalised spectral power between slow (200–300 Hz) and fast bands (300–400 Hz) | Hemibody tremor | Levodopa-induced changes |
R2 = 0.02 p = 0.37 |
|
| Weber et al. (2020) [60] | 19/38 | Differential entropy | Hemibody rigidity | Off | |
| 19/38 | Differential entropy | Hemibody tremor | Off | ||
| Belova et al. (2021) [61] | 22/35 | Amplitude of movement-related power increase (30–60 Hz) | Total UPDRS-III | Off |
R2 = 0.00 p = 0.60 |
aOutcomes are reported as explained variance (R2) computed from Pearson’s correlation coefficient or as Spearman’s rho (ρ). Values are rounded to two digits. The R2, ρ, or p value is left blank in case no information was provided by the original study
bTotal UPDRS-III and UPDRS scores for bilateral signal features (e.g. connectivity measures) were not lateralised. The number of included hemispheres is adjusted accordingly
cCorrelations for bradykinesia and rigidity items are listed separately as average in case no combined bradykinesia + rigidity category was included in the original study