tDCS application to the DLPFC is associated with the improvements of executive function, memory enhancement, language, processing speed, global cognitive symptoms and apathy over time after treatment. DLB is the second most common form of degenerative dementia. There is no FDA-approved medications that can slow, stop or improve the progression of cognitive declines in DLB. Identifying effective treatments is a critical issue for DLB. In neuropathology, extracelluar α-syn oligomers interfere with the expression of long-term potentiation(LTP), and influence memory and learning. tDCS has been proposed to affect long-term synaptic plasticity through LTP and long-term depression, thereby improving cognitive ability. So far, only two studies have evaluated the effect of tDCS in DLB. In this pilot study, we investigate the effect of tDCS on left DLPFC in DLB.

Fourteen DLB aged 55-90 years (mean age 76.4, with 4 males and 10 females) were included in a double-blind, randomized, sham-controlled cross over design study. DLB diagnostics is according to DSM-5 criteria. CDR ratings for DLB participants ranged from 0.5 to 2. The active tDCS (or sham) process consists of daily sessions of active tDCS (or sham) for 10 consecutive days. The anodal electrode was placed over the left DLPFC and the cathodal electrode was placed over the right supraorbital area, with a current intensity of 2 mA and an electrode size of 25 cm2 for 30 min in a session. Before and after these treatment sessions, all subjects received a series of neuropsychological tests, including CDR, MMSE, CASI, NPI and WCST. Chi-square test, Wilcoxon signed ranks test and Mann-Whitney U test were used to assess differences in participant demographic characteristics and to compare differences among groups.

The active tDCS group showed significant improvements on the three items of CASI, ‘language ability’, ‘concentration and calculation’, ‘categorical verbal fluency’, after active stimulations. There is no improvement in MMSE, CASI, NPI and WCST scores in the sham groups.

These results suggest that left DLPFC anodal, and right deltoid cathodal tDCS, may have some cognitive benefits in DLB. Larger-scale trials are needed to confirm the effect of tDCS in DLB.

Key words: Transcranial Direct Current Stimulation, Dementia with Lewy Bodies, cognitive function, Wisconsin Card Sorting Test, left DLPFC