Effects of Transcranial Direct Current Stimulation (tDCS) in the Normalization of Brain Activation in Patients with Neuropsychiatric Disorders: A Systematic Review of Neurophysiological and Neuroimaging Studies

Table 1

Summary of included studies.

Study [first author (year)]

Patient characteristics

Experimental details

Outcome measures

Diagnosis

Total

Age group

Concurrent mediation

Mode^†

Montage^‡

Duration (min)

Total number of sessions

Intensity (mA)

Therapy/task accompanied by tDCS

Modality (EEG/fMRI): paradigm

Behavioral/clinical findings (; active vs. sham)

Brain-behavior relationship ()

Schizophrenia

Kim (2019) [35]

Schizophrenia

11

Adult

Yes

Expt 1: bilateral

Anode: P4; Cathode: P3

20

1

2

Nil

fMRI: illness awareness task

fMRI illness awareness task; (i) Level of insight: n.s.

Correlations between interhemispheric imbalance in CBF and clinical scores: n.s.

11

Expt 2: bilateral

Anode: F4; Cathode: F3

30

1

2

Nil

fMRI: illness awareness task

Orlov (2017) [45]

Schizophrenia

24

Adult

Yes

Anodal

Anode: F3; Cathode: Fp2

30

1

2

Working memory task (-back)

fMRI: working memory task (-back)

fMRI -back task; (i) RT: n.s.

Significant correlation between the 2-/3-back performance 1 day after tDCS and the increased activation in L DLPFC ()

Stroop task

fMRI: stroop task

fMRI stroop task; (i) ACC: n.s.

Significant correlation between accuracy performance in the incongruent condition activation in the ACC ()

Rassovsky (2018) [46]

Schizophrenia

37

Adult

Yes

Expt 1: anodal

Anode: F3; Cathode: Fp2

20

2

2

Nil

EEG: auditory oddball task

Clinical assessment performance (ACC); (i) Speed of processing: n.s.; (ii) Working memory: n.s.; (iii) Verbal memory: n.s.; Reasoning and problem solving: n.s.

Correlation between EEG results from the active group and cognitive scores: n.s.

EEG: emotion recognition task

37

Expt 2: cathodal

Cathode: F3; Anode: Fp2

20

2

2

Nil

EEG: auditory oddball task

EEG: Emotion recognition task

Reinhart (2015) [47]

Schizophrenia

17

Adult

Yes

Anodal

Anode: FCz; Cathode: R cheek

20

1

1.5

Nil

EEG: feedback-based learning task

EEG feedback-based learning task; (i) RT: n.s.

Gain in ERN amplitude correlated with lower delusion score ()

Dunn (2016) [48]

Schizophrenia

24

Adult

Yes

Expt 1: anodal

Anode: Fp1, Fp2; Cathode: R upper arm

20

2

1

Nil

EEG: auditory oddball task

Not stated

Not stated

EEG: passive attention auditory duration deviant paradigm

24

Expt 2: cathodal

Cathode: Fp1, Fp2; Anode: R upper arm

20

2

1

Nil

EEG: auditory oddball task

EEG: passive attention auditory duration deviant paradigm

Impey (2017) [43]

Schizophrenia

12

Adult

Yes

Expt 1: anodal

Anode: between C5 and T7; Cathodal: Fp2

20

1

2

Nil

EEG: auditory oddball task

Behavioral working memory task (2-back); (i) RT: n.s.; (ii) ACC: n.s.

Not stated

12

Expt 2: anodal

Anode: F3; Cathode: Fp2

20

1

2

Nil

Behavioral working memory task (2-back); (i) RT: (); (ii) ACC: ()

Greater frontal MMN change correlated with faster RT ()

Knechtel (2014) [49]

Schizophrenia

14

Adult

Yes

Anodal

Anode: F3; Cathode: Fp2

20

1

2

Nil

EEG: go/no-go task

EEG go/no-go task; (i) ACC: n.s.

Not stated

Substance abuse

Mondino (2018) [50]

Tobacco abuse

24

Adult

No

Anodal

Anode: between F4 and Fp2; Cathode: between O1 and T5

20

10

1

Nil

fMRI: visual oddball task (smoking-related vs. neutral)

Reduction in craving: ()

R PCC increase in activation does not correlate with changes in cigarette consumption: n.s.

den Uyl (2016) [44]

Alcohol abuse

39

Adult

No

Anodal

Anode: F3; Cathode: Fp2

15

3

1

Nil

EEG: visual oddball task (alcohol-related image vs. neutral image)

Reduction in craving: n.s.

Not stated

Conti (2014) [51]

Crack-cocaine abuse

13

Adult

No

Bilateral

Anode: F4; Cathode: F3

20

1

1

Nil

EEG: visual oddball task (crack-related image vs. neutral image)

Not stated

Not stated

Depression

Nord (2019) [52]

Depression

39

Adult

No

Anodal

Anode: F3; Cathode: L deltoid

20

8

1

60-minute cognitive behavioral therapy with senior CP (symptom relief)

fMRI: working memory task (-back)

fMRI -back task: (i) RT: n.s.; (ii) ACC: n.s.

Correlation between increased bilateral DLPFC activation and -back improvement: n.s.

fMRI: emotional processing task

(i) fMRI emotional processing task; (ii) ACC: n.s.

Correlation between amygdala activation and emotional processing task: n.s.

Neurodevelopmental disorders

Sotnikova (2017) [53]

Attention deficit/hyperactivity disorder

16

Adolescent

No

Anodal

Anode: F3; Cathode: Cz

20

1

1

Working memory task (-back)

fMRI: working memory task (-back)

fMRI -back task ACC: <0.05 ()

Not stated

Breitling (2020) [54]

Attention deficit/hyperactivity disorder

15

Adolescent

No

Expt 1: anodal

Anode: F8; Cathode: Fp1

20

1

1

Working memory task (-back)

EEG: working memory (-back)

EEG -back task; (i) ACC: n.s.; (ii) RT: n.s.

Not stated

15

Expt 1: anodal (HD-tDCS)

Anode: F8 with 4 surrounding cathodes

20

1

0.5

Working memory task (-back)

EEG -back task; (i) ACC: n.s.; (ii) RT: n.s.

Rahimi (2019) [42]

Dyslexia

17

Children

No

Expt 1: anodal

Anode: T7; Cathode: R shoulder

20

1

1

Nil

EEG: gap detection task

(i) EEG gap detection task temporal perception: ()

Not stated

17

Expt 2: bilateral

Anode: T7; Cathode: T8

20

1

1

Nil

(i) EEG gap detection task ACC: ()

Neurodegenerative disorders

Das (2019) [55]

Mild cognitive impairment

16

Elderly

No

Anodal

Anode: F7; Cathode: R shoulder

20

8

2

Reasoning and inferencing strategy training

fMRI: resting

Clinical assessment performance (ACC); (i) Task switching: (); (ii) Strategic learning: (); (iii) Episodic memory: ()

Correlation between regional CBF and clinical improvement: n.s.

Meinzer (2015) [33]

Mild cognitive impairment

18

Elderly

No

Anodal

Anode: F7; Cathode: Fp2

20

1

1

Semantic memory task

fMRI semantic word retrieval task

fMRI semantic word retrieval task; (i) ACC: ()

Correlation between changes in activation and reduction in errors: n.s.

^†Mode of stimulation was classified based on a previously published framework [56]. ^‡Montage location was reported according to the EEG 10-20 system; the anatomical positions were reported for extracephalic montage. Expt: experiment; : number of participants; EEG: electroencephalography; fMRI: functional magnetic resonance imaging; L: left; R: right; n.s.: nonsignificant (at significance level); RT: reaction time; ACC: accuracy; ACC: anterior cingulate gyrus; PCC: posterior cingulate cortex; DLPFC: dorsolateral prefrontal cortex; ERN: event-related negativity; MMN: mismatch negativity; HD-tDCS: high-definition transcranial direct current stimulation; CBF: cerebral blood flow.