Preliminary Neuropsychological Outcomes in a Randomized Controlled Trial of High-Definition Transcranial Direct Current Stimulation in Alzheimer's Clinical Syndrome

The Alzheimer's Clinical Syndrome (ACS) is marked by global cognitive decline, and neural circuit dysfunction involving the dorsal anterior cingulate cortex (dACC) has been associated with some of the episodic memory and non-memory deficits in ACS. High-definition transcranial direct current stimulation (HD-tDCS) is a promising noninvasive treatment to lessen cognitive deficits in ACS, and this preliminary double-blinded trial examined whether HD-tDCS targeting the dACC could improve cognitive performance in ACS.Ten patients diagnosed with ACS (M age = 71.500; SD = 9.755) were randomized to receive sham (n = 2), 1 mA (n = 5), or 2 mA (n = 3) multi-electrode (4 cathodes x 1 anode) HD-tDCS for 10 daily sessions. Episodic memory, language, attention, and executive function measures were administered pre- and immediately post-treatment, and composite memory and non-memory scores were calculated. Paired samples t-tests examined significant differences (p < 0.05) between pre-treatment and post-treatment scores for each HD-tDCS group.For all three HD-tDCS groups, there were no significant improvements between pre-treatment and post-treatment scores for memory or non-memory abilities (p's > 0.05).This preliminary study showed that HD-tDCS applied over the dACC was unassociated with cognitive improvement in ACS. Future research with a larger sample will be needed to inform if this configuration of HD-tDCS could ameliorate cognitive deficits in ACS. Moreover, evaluation of HD-tDCS applied over other brain regions may yield additional insights, and a critical step will be to identify whether any clinical characteristics such as disease stage may influence the response to stimulation in ACS.