TABLE 8.

Studies and experimental characteristics of tES literature for stroke.

Authors	Subjects	Stimulation parameters				Neuroim aging		Conclusion
		Type	Current	Duration	Location	Type	Feature
Mane et al., 2019	19	tDCS	1 mA, 20 min	10 sessions	Anode: ipsilesional primary motor cortex, cathode: contralesionally primary motor cortex	EEG	Power spectral in delta (1–4 Hz), theta band (4–7.5 Hz), alpha (7.5–12.5Hz), beta (12.5–30 Hz), and correlation analysis.	QEEG features can act as prognostic and monitory biomarkers. tDCS-BCI can be pursued to predict a patient’s expected response to an intervention uniquely.
Bao et al., 2019	30	HD-tDCS	1 mA, 10 min	4 sessions	Anode: ipsilesional motor cortex(C3), cathode: frontal-parietal cortex (F1, F5, P1, P5)	EEG	Cortico-muscular coherence and power spectral in alpha (8–13 Hz), beta (13–30 Hz), and low gamma (30–48 Hz).	Anode HD-tDCS induced significant CMC changes in stroke subjects. The largest neuromodulation effects were observed at 10 min immediately after anodal HD-tDCS.
Hordacre et al., 2018	10	tDCS	1 mA, 20 min	1 session	Anode: primary motor cortex, cathode: contralateral orbit	EEG	Connectivity in different frequency band delta (1–3 Hz), theta (4–7 Hz), alpha (8–13 Hz), low beta (14–19 Hz), high beta (20–0 Hz), and gamma (31–45 Hz).	Alpha band functional connectivity of an approximate ipsilesional sensorimotor and contralesionally motor-premotor network is a robust and specific biomarker of neuroplastic induction following anodal tDCS in chronic stroke survivors.
Nicolo et al., 2018	41	tDCS	1 mA, 25 min	3 sessions per week for 3 weeks	Anode: ipsilesional supraorbital region, cathode: contralesionally primary motor cortex	EEG	Effective connectivity and functional connectivity	The inhibition of the contralesionally primary motor cortex or the reduction of interhemispheric interactions was not clinically useful in aheterogeneous group of subacute stroke subjects. Enhancement of perilesional beta-band connectivity through tDCS might have more robust clinical gains if it started within the firstfour weeks after the onset of stroke.
Naros and Gharabaghi, 2017	20	tACS	1.1 mA, 20 Hz, 20 min	1 session 5 sessions per week for 3 weeks	Anode: ipsilesional sensorimotor cortex, cathode: contralesionally forehead.	EEG	Ipsilesional and contralesionally beta power in resting state and event related desynchronization	Intermittent β-tACS reduces the instantaneous variance of sensorimotor β oscillations and increases the specificity of brain self-regulation-based neurofeedback in patients with stroke patients.
Yuan et al., 2017	9	tDCS	1.2 mA, 20 min		Anode: primary sensorimotor cortex, cathode: contralateral shoulder	EEG	Approximate entropy	After tDCS, scores of swallowing apraxia assessments increased, and ApEn indices increased in both stimulated and non-stimulated areas.
D’Agata et al., 2016	34	tDCS	1.5 mA, 20 min	10 daily sessions for 2 weeks	Anode: damaged hemisphere corresponding to motor cortex (C3 or C4), cathode: opposite hemisphere	EEG	Event-related potential (P300, N200)	NIBS generally improved ERP, but transitorily. More than one NIBS cycle (2–4 weeks) should be used in rehabilitation to obtain clinically relevant results after a washout period only in responder patients.
Dutta et al., 2015	4	tDCS	0.526 A/m2, 15 min	1 session	Anode: motor cortex (Cz), cathode left supraorbital notch	EEG and fNIRS	The concentration changes of HbO and HbR, power spectrum	The initial dip in HbO2 at the beginning of anodal tDCS corresponded with an increase in EEG’s log-transformed mean power within the 0.5 Hz –11.25 Hz frequency band.
Kasashima-Shindo et al., 2015	18	tDCS	1 mA, 10 min	5 days per week for 2 weeks	Anode: primary sensorimotor cortex of the affected hemisphere, cathode: contralateral supraorbital area.	EEG	Event-related desynchronization	Event-related desynchronization was significantly increased in the tDCS- brain-computer interface group; anodal tDCS can be a conditioning tool for brain-computer interface training in patients with severe hemiparetic stroke.
Wu et al., 2015	12	tDCS	1.2 mA, 20 min	5 sessions per week for 4 weeks	Anode: left posterior peri-sylvian region, cathode: unaffected shoulder	EEG	Approximate entropy	A-tDCS over the left PPR coupled with speech-language therapy can improve picture naming and auditory comprehension in aphasic patients. Moreover, tDCS could modulate the related brain network, not only the stimulated brain areas.
Jindal et al., 2015	29	tDCS	0.526 A/m2, 3 min	1 session	Anode: motor cortex (Cz), cathode: frontal cortex (F3 or F4)	EEG and fNIRS	The concentration changes of HbO and HbR, power spectrum	Anodal tDCS can perturb local neural and vascular activity, which can be used for assessing the functionality of regional cerebral microvessels where crematory clinical studies are required in small vessel diseases.
Dominguez et al., 2014	1	tDCS	1 mA, 20 min	5 sessions per week for 3 weeks	Anode: left frontal area. cathode: homologous right contra-lateral area	EEG	Coherence and power spectrum in the delta (0–4 Hz), theta (4–8 Hz), alpha (8–13 Hz), and beta (13–30 Hz) bands.	tDCS can be affected for behavioral performance and inhibit the irregular activity in the right hemisphere. A longer stimulus can produce greater recovery.
Kasashima et al., 2012	6	tDCS	1 mA, 10 min	1 session	Anode: primary motor cortex of the affected hemisphere, cathode: opposite side in thesupraorbital region	EEG	Event-related desynchronization	Anodal tDCS can increase mu ERD of the affected hemisphere in patients with severe hemiparetic stroke as well as in healthy persons.
Ang et al., 2015	19	tDCS	1 mA, 20 min	5 sessions per week for 2 weeks	Anode: silent area. cathode: most active interictal epileptiform discharges area	EEG	Seizure frequency and laterality coefficient.	tDCS improved the motor ability assessment score, and EEG laterality coefficients were improved after the intervention.