Table 2.
Studies of tDCS on cognitive functions.
| Study | Healthy subjects/age (age: mean [± standard deviation] or range) | Stimulation electrode | Polarity | Duration/intensity | Side effects | Effects |
|---|---|---|---|---|---|---|
| Andrews et al. (2011) | 10, 20−51 years | Left DLPFC | Anodal/sham | 10 min, 1 mA | No | Improvement in a WM task after atDCS |
| Boggio et al. (2006) | 18 Patients with PD, 45−71 years | M 1, left DLPC | Anodal/sham | 20 min, 1 or 2 mA | No | Improvement in WM of Parkinson’s disease patients after atDCS of the left DLPFC |
| de Vries et al. (2011) | 38, 23 ± 2 years | Broca’s area | Anodal/sham | 20 min, 1 mA | No | atDCS facilitates the acquisition of grammatical knowledge |
| Ferrucci et al. (2008b) | 13, 75 ± 7 years | Cerebellum | Anodal/cathodal/sham | 15 min, 2 mA | Headache (one patient) | atDCS and ctDCS impairs practice-dependent proficiency in WM |
| Fiori et al. (2011) | 10 Subjects, 3 patients, 45−70 years | Wernicke’s area | Anodal/sham | 20 min, 1 mA | No | atDCS improved accuracy on the picture-naming task, both normal and patients had a shorter naming latency during atDCS |
| Flöel et al. (2008) | 19, 26 ± 3 years | Cp5 | Anodal/cathodal/sham | 20 min, 1 mA | No | Enhanced language learning by atDCS |
| Flöel et al. (2011) | 20, 62 ± 9 years | Right temporoparietal cortex | Anodal/sham | 20 min, 1 mA | No | Improved recall one week after learning with atDCS |
| Fregni et al. (2005) | 15, 19−22 years | M1, DLPFC | Anodal/cathodal/sham | 10min, 1mA | No | atDCS leads to enhancement of WM performance |
| Iyer et al. (2005) | 103, 19−70 years | F3 | Anodal/cathodal/sham | 20 min, 1 mA | Skin redness | Enhanced verbal fluency by atDCS |
| Javadi and Walsh (2011) | 32, 23 ± 2 years | Left DLPFC, M1 | Anodal/sham | 20 min, 1 mA | No | Enhancement of verbal memorization after atDCS or impairment of verbal memorization after ctDCS |
| Kincses et al. (2004) | 22, 28 ± 5 years | Fp3 | Anodal/cathodal | 10 min, 1 mA | No | atDCS enhanced probabilistic classification learning |
| Marshall et al. (2004) | 13, 19−28 years | F3 and F4 | Anodal/sham | Alternating 15 s off/15 s on over 30 min | No | atDCS during slow wave sleep improves verbal declarative memory |
| Marshall et al. (2005) | 12, 19−27 years | F3 and F4 | Anodal/cathodal | Alternating 15 s off/15 s on over 15 min | No | Impaired performance in WM task by anodal and ctDCS |
| Ohn et al. (2008) | 15, 27 ± 4 years | F3 | Anodal/sham | 30 min, 1 mA | No | atDCS enhanced performance in a WM task |
| Penolazzi et al. (2010) | 11, 27 ± 5 years | Right F4–C4, Left F3–C3, alternating between atDCS and ctDCS | Anodal/cathodal/sham | 20 min, 1 mA | No | Right atDCS and left ctDCS facilitated the recall of pleasant images regarding pleasant and neutral images |
| Ross et al. (2011) | 14, 55−69 years | Both anterior temporal lobes | Anodal/sham | 15 min, 1.5 mA | No | Numerical improvement in face naming after atDCS |
| Sparing et al. (2008) | 15, 27 ± 4 years | Cp5 | Anodal/cathodal/sham | 7 min, 2 mA | No | Improved picture naming by atDCS |
| Teo et al. (2011) | 12, 27 ± 9 years | F3 of the DLPFC | Anodal/sham | 20 min, 1 mA | No | Current strength may affect WM performance |
| Zaehle et al. (2011) | 10, 25 ± 2 years | Left DLPFC | Anodal/cathodal | 15 min, 1 mA | No | Increase in WM performance and amplified oscillatory power in theta and alpha bands after atDCS, interference with WM performance after ctDCS |
Abbreviations for electrode placement according to the 10–20 electrode system (Cp5, Cz, Fp3, C3/4: see Recommendations for the practice of clinical. Neurophysiology: guidelines of the International Federation Clinical Neurophysiology. Electroencephalogr. Clin. Neurophysiol. Suppl. 1999;52:1–304), atDCS, anodal transcranial direct current stimulation; min, minutes, ctDCS, cathodal transcranial direct current stimulation, DLPFC, dorsolateral prefrontal cortex; mA, milli Ampere; min, minutes, PD, Parkinson’s disease; TPC, temporoparietal cortex.