Saccadic Eye Movement Control Behaviour in Healthy Adults: Investigations of Clinically Practical Anodal Transcranial Direct Current Stimulation Protocols

Abstract

Ageing is associated with declines of cognitive functions, including voluntary control over eye movements, which could be due to natural brain deteriorations. In relation to frontal-lobe deterioration, adult ageing adversely impacts voluntary saccadic eye movement control in particular. Not only this age-related deficit compromises effective performance of daily activities, it might also indicate the transition from healthy to pathological ageing. Recent research indicates that anodal transcranial direct current stimulation (tDCS) over the frontal eye field (FEF) can be used to improve saccadic eye movement control in healthy young adults. My PhD research sets out to replicate these findings using more clinically practical protocols, and to test whether tDCS over the dorsolateral prefrontal cortex (DLPFC) might afford even greater benefits, and to determine whether these benefits extend to older adults. The findings revealed no improvements in saccadic performance following active anodal tDCS relative to control conditions in either young or older adults. The negative results call into question whether the protocol utilised can be applied effectively without localisations of the relevant frontal subregions via neuroimaging or other specialist tools. In conclusion, the development of a clinically practical tDCS protocol in counteracting age-related deficits in voluntary eye movement control remains to be explored. Future efforts should consider administering online tDCS training to promote plasticity, together with, multiple stimulation sessions, higher current strengths and longer stimulation duration, and/or combination with physical exercise, that might prove fruitful to improve saccadic eye movement control in older adults.