Long-term empowerment effect of executive functions by multisession neuromodulation in healthy aging: follow-up evidences

Non-Invasive Brain Stimulation (NIBS) techniques proved to be valuable tools in supporting cognitive empowerment in case of both neurodegenerative diseases and functional impairments due to cerebrovascular events. However, little research systematically explored their potential contribution to containment and prevention of physiological cognitive decline in healthy aging. Further, the majority of those studies actually focused on the effect of single stimulation sessions with limited investigation of their long-term maintenance. The present report extends previous finding concerning short-term empowerment effects of an integrated multi-session neuromodulation protocol on executive functioning by showing intervention-related long-term effects in a sample of healthy elderly people. In order to explore perceived sustainability and short/long-term intervention outcomes, we divided 23 participants into a control and an experimental group and asked them to complete a standardized neuropsychological and electrophysiological (i.e. recording of event-related potentials during an executive attention task) assessment at the beginning of the study (T0), at the end of the intervention period (T1) and after further six months (T2). The integrated intervention protocol lasted eight weeks and included three anodal transcranial Direct Current Stimulation (tDCS) sessions (15 minutes, 1.5 mA, right prefrontal placement with contralateral supraorbital cephalic reference) per week with twice-weekly executive functions tasks. Mixed effects models accounting for subjectrelated and time-related confound highlighted relevant performance increases in the experimental group with respect to the control one at the end of the intervention. In particular, we observed higher scores at standardized tests tapping on executive functions (abstract reasoning, cognitive flexibility and verbal generation) and enhanced automatic attention responses. Such improvements were partially maintained even at the follow-up. To sum up, the multisession neuromodulation protocol proved to be able to induce empowerment of specific cognitive abilities even in healthy aging, with interesting long-term effects. Our findings support the notion that integrated neuromodulation protocols may offer valuable intervention opportunities for cognitive decline prevention.