F148. tDCS-enhanced working memory training in subjective cognitive decline

Abstract

Introduction Subjective cognitive decline (SCD) is defined as worsening of cognitive abilities, although examination fails to reveal objective evidence of this decline. SCD is increasingly acknowledged as a risk factor for the development of Alzheimer’s disease and is therefore considered a stage particularly accessible for interventional strategies. However, studies evaluating the efficacy of therapeutic interventions in this condition are scarce. Of note, SCD has been particularly linked with deficient cognitive control (CC) functions. Anodal transcranial direct current stimulation (tDCS) to the left dorsolateral prefrontal cortex (dlPFC) can significantly enhance CC. Specifically, this has been demonstrated by means of a challenging and frustrating continuous performance task (Paced Auditory Serial Addition Task; PASAT). This randomized, sham-controlled study aims at providing evidence for the efficacy of a tDCS-enhanced CC training (PASAT) in participants with SCD. Methods 30 subjects with SCD (age > 60 years) participated in a four weeks training (12 sessions). Half of them received 2 mA anodal tDCS for 20 min applied to the left dlPFC, a major hub of the cognitive control network; the other half received sham stimulation. Eligibility criteria were examined by means of neuropsychological tests (CERAD-Plus, M.I.N.I.). The amount of concerns regarding memory impairment, which was quantified by means of a 10-point Likert scale, was obtained before and after the tDCS-enhanced training (pre- and post-session) and served as the primary outcome measure. Event-related potentials were measured with EEG as neurophysiological signatures of cognitive control. Near and far transfer were assessed by a Verbal 2-back Task and the Trail Making Test A & B. Together with changes of PASAT performance these measures were obtained before and after the tDCS-enhanced training. A follow-up session was conducted 3 months after end of training to control the sustainability of the training effects. Results A one-way repeated measures ANOVA showed that, compared to sham stimulation, anodal tDCS during PASAT training significantly reduced the amount of concerns regarding memory impairment ( F (1, 28) = 6.48, p = 0.017, η p 2 = 0.18). This effect was maintained at follow-up ( F (1, 28) = 4.33, p = 0.047, η p 2 = 0.13). Performance in the PASAT task was improved by training (t(324) = 8.84, p Conclusion In summary, the current study suggests that anodal tDCS-enhanced Cognitive Control Training in subjects with SCD results in reduction in the amount of worries regarding memory impairment, which persists for up to 3 months. This proof of concept could provide a basis for potential interventional approaches in SCD. Further studies are needed to replicate these results on a larger scale.