Neuromodulation (tDCS) effect on executive functions in healthy aging: clinical and EEG evidences

Physiological aging is a dynamic process that, despite an increase in physical and cognitive frailty, gives opportunities for maintaining and strengthening the quality of physiological, cognitive and emotional processes. As suggested by research on cortical plasticity, the re-activation of networks mediating cognitive functions by means of cognitive and electrophysiological interventions may lead to an improvement of function-specific and global functioning. In particular, brain stimulation techniques proved to efficaciously increase performances and functional profile of patients affected by neurodegenerative disorders, but their potential contribution in the empowerment of healthy elderly and prevention of cognitive decline is understudied. Moreover, traditional neuromodulation protocols usually measure treatment outcomes in terms of behavioural performances, while the integration with psychophysiological measures might help in depicting a clearer picture. The present research aims at investigating the efficacy of a non-invasive brain stimulation protocol (tDCS) applied to prefrontal areas in empowering executive functions and automatic attention responses (ERPs) in healthy elderly people. 22 volunteers took part to the study and were assigned to the treatment (11 participants) or control (11 participants) group. Both groups were tested at T0 and re-tested after three months (T1). The assessment procedure included both a series of standardized neuropsychological tests aimed at sketching a complete picture of individual cognitive profile and the recording of electroencephalographic responses during a challenging computerized attentional task. The tDCS intervention protocol lasted 8 weeks and included three stimulation sessions per week (15 minutes, 1.5 mA, anodal placement over right dlPFC with cephalic reference), with twice-weekly administration of tasks tapping on non-verbal executive functions. Analyses comparing T0 and T1 data of the experimental and control groups showed a significant increase in post-intervention performances for participants undergoing the tDCS protocol, in particular with respect to non-verbal and verbal executive functions – i.e. Raven’s Progressive Matrices total score, errors at the Stroop’s test, and verbal associative fluency. At the end of the empowerment protocol, the neuromodulation group also showed early differences in attention-related ERPs for incongruent stimuli in a computerized Stroop-like task. Present evidences suggest that a non-intensive neuromodulation protocol may mediate the empowerment of specific cognitive functions in healthy aging people by capitalizing on brain and cognitive reserve, and hint at interesting practical implication for prevention and early intervention.