Table 1.

Summary table of articles exploring gamma stimulation in patients with MCI/AD and animal models of AD.

Author, year	Population	Study Design	Session Number	Session Duration (mins)	Stimulation Parameters	Stimulation Location	Concurrent Task	Task	Cognitive Domain	Outcome Measures	Results
Benussi et al., 2021	MCI/AD patients	Within- subject crossover	1	60	Conventional tACS; 40 Hz gamma; 3 mA peak-to-peak intensity	Anode: medial parietal cortex/ precuneus (Pz); Cathode: right deltoid muscle	Online, offline	Rey auditory verbal learning (RAVL) test, Face-name associations task (FNAT)	Episodic memory	Accuracy on RAVL and FNAT	Active tACS showed significant improvement on RAVL and long delayed recall scores compared to sham stimulation.
Benussi et al., 2022	MCI/AD patients	Within-subject crossover	1	60	Conventional tACS; 40 Hz gamma; 3 mA peak-to-peak intensity	Anode: medial parietal cortex/ precuneus (Pz); Cathode: right deltoid muscle	Online, offline	RAVL and FNAT	Episodic memory	Accuracy on RAVL and FNAT; Gamma EEG activity (pre-post change); Cholinergic levels (pre-post change)	Active tACS showed significant improvement on RAVL immediate and delayed recall scores compared to sham. FNAT scores improved after active but not sham. Cholinergic levels increased after active tACS but not sham. Increased gamma in parietal lobes correlated with task improvements.
Bréchet et al., 2021	AD patients	Open label pilot study	70	20	HD-tACS; 40 Hz gamma; 4 mA peak-to-peak intensity	Anodes: left angular gyrus (BA39/40); Cathodes: C3, P2, P7, T7	Offline	Autobiographical memory task	Episodic memory	MoCA (non-visual version); Memory Index Score (NACC UDS)	Improvement in cognitive testing every 2 weeks over 14 week intervention compared with baseline performance; study demonstrated feasibility and safety of home-based tACS.
Dhaynaut et al., 2020	Mild to moderate AD patients	Open label pilot study	20	60	tACS; 40 Hz gamma; intensity not reported	Anode/Cathode: bilateral temporal lobes	N/A	N/A	N/A	PET imaging: amyloid-β, p-Tau, and microglia	Trend of decreased intracerebral Tau burden in 3/5 patients; intracerebral amyloid-p and microglial activation was not influenced by tACS.
Dhaynaut et al., 2022	Mild to moderate AD patients	Proof of principle case series	20	60	tACS; 40 Hz gamma; 2 mA intensity	Anode/Cathode: bilateral temporal lobes (T7-T8; P7-P8)	N/A	N/A	N/A	PET imaging: amyloid-β, p-Tau, and microglia EEG: Gamma spectral power	Significant decrease of 2% p-Tau burden in 3/4 patients; decrease in microglia activation in 1/4 patients; intracerebral amyloid-β was not influenced by tACS; gamma spectral power increased from baseline to post-treatment.
Iaccarino et al., 2016	Multiple mouse models of AD	Between-subject	1	60	Light flicker (20, 40, or 80 Hz) versus random flicker or dark exposure	Targeting primary visual cortex	N/A	N/A	N/A	Levels of amyloid-β and microglia in visual cortex	Reduction of amyloid-p peptides and concomitant microglial response in the visual cortex after 40 Hz gamma entrainment, over 20 Hz, 80 Hz, and random flicker or darkness conditions.
Kehler et al., 2020	MCI/mild to moderate dementia patients	Between-subject	40	60	tACS; 40 Hz gamma; 1.5 mA peak-to-peak intensity	Anode: left dorsolateral prefrontal cortex (F3); Cathode: contralateral supraorbital area	Online, offline	MindTriggers: brain exercises; Wechsler Memory Scale (WMS-IV)	Memory function: verbal, auditory, visual, shortterm, and working memory	WMS-IV score (pre-post change score)	Active and sham groups significantly improved on WMS immediately after intervention. Active tACS maintained improvements significantly better than sham at one month followup.
Park et al., 2022	Mouse model of AD	Between-subject	72	46.67	Light flicker (40 Hz) + treadmill exercise	Targeting primary visual cortex	N/A	N/A	N/A	Levels of amyloid-β, tau, apoptosis and inflammatory markers	Light flicker (40 Hz) + exercise over dark condition significantly reduced amyloid-β, tau protein levels, and apoptosis.
Sprugnoli et al., 2021	Mild to moderate AD patients	Open label pilot study	10 to 20 sessions	60	HD-tACS; 40 Hz gamma; 4 mA peak-to-peak intensity	Targeting right temporal lobe (T8)	Online	Viewing documentaries	Attention	Arterial Spin Label (ASL) MRI (pre-post change)	Blood perfusion significantly increased in bilateral temporal lobes after tACS treatment. Perfusion change positively correlated with changes in episodic memory and spectral power changes in gamma EEG activity.