Moderating effects of gender, age and cognitive reserve on combined cognitive training and transcranial electrical stimulation

Abstract Cognitive training (CT) has been shown to improve cognition in elderly adults via targeted exercises for single or multiple cognitive domains. Combining CT with brain stimulation is thought to be more effective due to synergistic effects in the targeted brain areas and networks. However, little is known about the moderating effects of gender, age, and cognitive reserve on cognitive outcomes. In this randomized, sham-controlled study, 59 healthy elderly participants (mean age 71.7) were assigned to receive computer-based CT (10 sessions, 50 min, twice weekly). During first 20 minutes of each CT session participants received either tDCS (2 mA), tACS (1 mA, 5 Hz, 0° initial phase shift), or sham stimulation. The anode was placed over the left dorsolateral prefrontal cortex (35 cm2), the cathode (100 cm2) was placed over the supraorbital area. Participants trained processing speed, selective and divided attention, and executive functions (working memory, inhibitory control). Cognitive performance was assessed with the Montreal Cognitive Assessment (MoCA), and a cognitive composite score derived from a broad neuropsychological test battery that was administered before and immediately after the intervention as well as at a 6- and 12-month follow-up. Cognitive reserve was assessed with the Cognitive Reserve Index questionnaire (CRIq). We will report on cognitive outcomes of each intervention against sham stimulation in finding differences between the different study groups. Further outcomes will provide information on the moderating effects of gender, age, and cognitive reserve. Finally, we will discuss possible implications of said moderating factors for the planning of combined cognitive training and brain stimulation studies. Research Category and Technology and Methods Translational Research: 5. Other Transcranial Electrical Stimulation (tES) Keywords: Transcranial direct current stimulation, Transcranial random noise stimulation, Cognitive training, Aging