Transcranial direct current stimulation (tDCS) facilitates cognitive enhancement by directly increasing neuroplasticity, and has shown promising results as an external intervention to attenuate age-related cognitive decline. However, stimulation protocols have failed to account for age-associated changes in brain structure and the present literature omits investigation of attentional control, despite the occurrence of substantial inhibitory processing deficits with age. To provide new insight into the benefits of tDCS, the objective of this study was to develop an age-optimised stimulation protocol in which key parameters (amplitude, duration, and electrode configuration) were selected in accordance with knowledge of stimulation effects, specific to the ageing brain. Participants (mean age 66.5 years) completed three sessions of double-blind, anodal or sham stimulation, in conjunction with a novel task switching paradigm, which was designed to reflect the complexities of simultaneously monitoring and updating stimulus representations. The results show that those who had anodal tDCS exhibited an acute, post-stimulation increase in task switching speed (p < .01, d = 1.36). Although the sham group was subject to the same task exposure, only the anodal stimulation group experienced a performance gain, thus emphasising the efficacy of active brain stimulation. For the first time, this study demonstrates the utility of stimulation protocols tailored specifically for use with older adults, targeted towards the modulation of attentional control. This finding has critical implications for cognitive health and encourages the use of age-optimised tDCS as a viable method for enhancing executive function in later life.
Keywords: Attentional control; Healthy ageing; Neural plasticity; Task switching; Transcranial direct current stimulation.
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