LAUSR

Consistent with this notion, the negative impact of dual tasking on gait is exaggerated in freezers when compared with nonfreezers. Building on these ideas, Putzolu and colleagues present preliminary results suggesting that after a single session of real tDCS designed to “prime” the left DLPFC for activation, dual tasking had smaller negative effects on gait speed and several other gait metrics in freezers, but not in the nonfreezers. Notably, these dual-task costs became similar in magnitude to that observed in the nonfreezers, and no effect was observed after sham. The effects of tDCS on dual-task gait performance in those with FOG are intriguing and extend our previous work. In our earlier study, we applied multitarget stimulation using an array of gel electrodes to facilitate the excitability of M1 and the left DLPFC based on the idea that both motor and cognitive functions are involved in FOG. We observed positive effects on FOG, gait, and executive function in freezers. The work by Putzolu and colleagues supports the idea that deficits in higher level cognitive function contribute to FOG and, promisingly, that dual-tasking performance may be ameliorated via tDCS, at least in the short term. The results of Putzolu and colleagues are complementary to those that we reported earlier. There are, nonetheless, several methodological differences worth mentioning. Putzolu and colleagues used 2 relatively large sponge electrodes. In addition to facilitation of the excitability of the left DLPFC and other regions of the left hemisphere, this approach likely inhibited regions of the right hemisphere that may have also contributed to the observed effects on dual-task gait performance. The authors also did not compare the effects of stimulation targeting the left DLPFC with stimulation targeting other regions (eg, M1). In our work, we used an array of smaller gel electrics and a modeling-based optimization technique with the goal of maximizing facilitation of both MI and the left DLPFC while minimizing potential inhibitory effects of the stimulation. We, however, did not test the effects of stimulation targeting only the left DLPFC. Future work is thus needed to optimize tDCS for FOG, with careful consideration of the target areas, electrode placement, and current flow parameters. With this knowledge in hand, researchers will be better positioned to investigate the longer term effects of multiple sessions of tDCS, both alone and in concert with other evidenced-based approaches, to alleviate the burden of FOG in this vulnerable population.