Developing Clinically Practical Transcranial Direct Current Stimulation Protocols to Improve Saccadic Eye Movement Control

Abstract

Recent research indicates that anodal transcranial direct current stimulation (tDCS) applied over the frontal eye field (FEF) can be used to improve saccadic eye movement control in healthy young adults. The current research set out to replicate these findings using a clinically practical protocol, to test whether tDCS applied over the dorsolateral prefrontal cortex (DLPFC) might also afford benefits, and to determine whether benefits extend to older adults, who are known to suffer from saccadic eye movement control deficits. Twenty young and 10 older adults completed two active (FEF and DLPFC) and one sham stimulation session. In an effort to aid clinical translation, the method of positioning the electrodes entailed simple measurements only. No improvements in saccadic performance emerged following anodal tDCS applied over the FEF or DLPFC relative to the sham condition in either age group. In addition, saccadic performance contralateral to the active electrodes showed no evidence of benefits over ipsilateral performance. These negative results question whether the protocol utilized can be applied effectively using only simple measurements to localize the relevant frontal subregion. Future efforts can consider adjusting the tDCS montage that might yield more promising results to improve saccadic eye movement control in older adults.

Bi-Anodal Transcranial Direct Current Stimulation Combined With Treadmill Walking Decreases Motor Cortical Activity in Young and Older Adults

“…Stimulating not only the area underlying the anodal electrode, but also surrounding areas within the regions may enhance the tDCS benefits. For example, Chen and Machado (2017) using a 3 cm × 3 cm anodal electrode did not show benefits on saccadic eye movement behavior, but Chen et al (2018) showed improvements in oculomotor control following tDCS using 5 cm × 7 cm anodal electrode. Secondly, the stimulation intensity may have been too low.…”