Table 4 Intervention protocols and results in studies that targeted the DLPFC
Study | Polarity of target electrode | Electrode size (cm2) | Intensity (mA) Current density (mA/cm2) | Current density (mA/cm2) | Duration (min) | Number of sessions | Anatomical target (target electrode placement) | Target electrode placement | Return electrode placement | State of medication during intervention | Combined intervention | Online/offline tDCS | Adverse effects | Outcome measurements | Time points of assessment | State of medication during assessment | Results | Conclusion | Effect size (type) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Bueno et al. 2019 [42] | Anode | T = R = 5 × 7 | 2 0.06 | 0.06 | 20 | 1 | DLPFC (F3) | F3 | Fp2 | NR | – | Offline | NR | TUG; Video gait analysis for time to cover a particular distance, gait speed, number of steps | Before, after | On | No improvement in TUG time and data from video gait analysis | → | NR |
Chang et al. 2017 [43] | Anode | T = R = 5 × 5 | 1 0.04 | 0.04 | 20 | 5 consecutive days | DLPFC (F3) | F3 | Contralateral supraorbital | On | Repetitive transcranial magnetic stimulation with 10 Hz frequency | Online | Headache | FoG questionnaire, modified Standing-Start 180° Turn Test (turning steps and turning time); TUG | Before, immediately and 1 week after 5 sessions of intervention | On | Significant improvement in FoG and ambulatory function in both groups. No significant difference in the between-group analyses | ↑ | NR |
Criminger et al. 2018 [51] | Anode, cathode | T = R = 3 × 5 | 2 0.13 | 0.13 | 20 | 1 | DLPFC (F3,F4) | F3, F4 | F3, F4 | On | Stationary bicycling; playing a video game of golf on Wii™ | Online | Headache | TUG in ST and DT conditions | Before, after | On | No significant effect of tDCS on TUG | → | NR |
Dagan et al. 2018 [44] | Anode | T = R = 3 (Pi-electrodes) | Max = 1.5 0.33 | 0.33 | 20 | 1 | M1, DLPFC (AF4, CP1, F3, FC1, FC5, Cz) | AF4, CP1, F3, FC1, FC5, Cz | NR | NR | – | Offline | NR | FOG-provoking test; gait speed in 40 m walking, TUG | Before, after | NR | TUG, gait speed in 40 m and FoG improved by only multitarget stimulation | M1 alone: →; M1 and DLPFC: ↑ | NR |
Lattari et al. 2016 [45] | Anode | T = R = 5 × 7 | 2 0.06 | 0.06 | 20 | 1 | DLPFC (F3) | F3 | Contralateral supraorbital | NR | – | Offline | Tingling, itching | Dynamic Gait Index; TUG | before, after | NR | Improvement in dynamic gait index and TUG | ↑ | NR |
Manenti et al. 2014 [47] | Anode | T = R = 5 × 7 | 2 0.06 | 0.06 | 7 | 1 | DLPFC (F3 or F4) | F3 or F4 | Contralateral supraorbital | On | – | Offline | No | TUG | Before, after | On | Decrease in TUG time comparing tDCS over F4 vs. sham tDCS | ↑ | NR |
Mishra et al. 2021 [39] | Anode | T = R = 5 × 7 | 2 0.06 | 0.06 | 30 | 1 | DLPFC (F3) | F3 | Contralateral supraorbital | On | – | Online/offline | – | Speed | Before, during, immediately, 15 min, and 30 min after stimulation under ST and DT conditions | On | Improvement of gait under DT condition | ↑ | NR |
Swank et al. 2016 [52] | Anode | NR | 2 | – | 20 | 1 | DLPFC (F3) | F3 | F4 | On | – | Offline | NR | TUG under three conditions: alone, with motor task, with cognitive task | Immediately after | On | No significant differences | → | 0.07 to 0.45 (Glass’ Δ) |