TABLE 6.

Studies and experimental characteristics of tFS literature for schizonhrenia.

Authors	Subjects	Stimulation parameters				Neuroim aging		Conclusion
		Type	Current	Duration	Location	Type	Feature
Boudewyn et al., 2020	37	tDCS	2 mA, 20 min	1 session	Anode: left dorsolateral PFC(F3), Cathode: right supraorbital site (FP2)	EEG	The power spectrum of the gamma band (30–80 Hz)	Gamma oscillations in proactive cognitive control and frontal tDCS may be a promising approach to enhancing proactive cognitive control in schizophrenia.
Jahshan et al., 2020	27	tDCS	2 mA, 20 min	3 sessions for one week	Anode: central occipital cortex, cathode: right shoulder.	EEG	Visual evoked potentials	It is no evidence of an input-specific plasticity effect and an inconsistent effect of tDCS delivered before visual stimulation on plasticity in people with schizophrenia.
Ahn et al., 2019	22	tACS and tDCS	1.5 or 2 mA, 10 Hz, 20 min	10 sessions	Anode: prefrontal cortex (F3, Fp1), cathode: T3, P3	EEG	Alpha oscillations, Power spectral density, functional connectivity.	tACS has potential as a network-level approach to modulate reduced neural oscillations in relation to clinical symptoms in patients with schizophrenia.
Rassovsky et al., 2018	38	tDCS	2 mA, 20 min	Twice daily for three visits	Anode: DLPFC, cathode: right supraorbital	EEG	P300 and N170	There was no significant improvement based on the results of the neurological and cognitive perspective after single-session tDCS.
Dunn et al., 2016	36	tDCS	1 mA, 20 min	1 session	Anode: bilateral DLPFC (FP1 and FP2), cathode:^ right upper arm	EEG	P300	tDCS can engage and modulate an EEG-based auditory processing measure in schizophrenia.
Hoy et al., 2015	16	tDCS	1 or 2 mA, 20 min	3 sessions			Gamma event-related synchronization and correlation.	tDCS may enhance working memory in schizophrenia by restoring normal gamma oscillatory function
					Anode: frontal cortex (F3), cathode: right supraorbital	EEG
Smith et al., 2015	19	tDCS	1.5 mA, 20 min	1 session	Anode: medial frontal cortex	EEG	Interregional phase synchrony, event-related potential. Power spectrum	Behavioral performance improved. These results provide unique causal evidence for theories of executive control and cortical dysconnectivity in schizophrenia.
Singh et al., 2019	9	tACS	1 mA, 20 min	1 session	Anode: cerebellar vermis, cathode: right shoulder	EEG	Mean relative power at delta (1–4 Hz) and theta (4–8 Hz) frequency bands	Theta oscillations were obtained. Single-session theta frequency stimulation may modulate task-related oscillatory activity in the frontal cortex.
Impey et al., 2017	12	tDCS	2 mA, 20 min	2 sessions	Anode: left auditory or frontal cortex, cathode: contralateral forehead.	EEG	Event-related potential	Anodal frontal tDCS significantly increased working memory performance, which positively correlates with mismatch negativity-tDCS effects.