 Additional secondary measures will test the influence of tDCS on other motor, cognitive or motor-cognitive functions related to PD and FOG. Secondary outcomes related to motor function, which are likely to be affected by changes in M1 excitability, will include gait speed usual walking, Timed Up Go scores, UPDRS motor scores, and level of activity over 7 days using portable, lightweight, water-proof sensors. Secondary measures of executive function, which are hypothesized to be responsive to tDCS of the DLPFC, will include the Trail Making test TMT parts A and B, and a previously validated computerized neuropsychological battery that provides normalized scores for executive function and attention and memory. Dual-tasking gait speed i.e., walking while performing a serial subtraction test will assess motor-cognitive interactions. Functional near infra-red spectroscopy available in Boston and Tel Aviv will assess frontal activation during dual-tasking walking; this reflects the subjects ability to handle cognitive loading and has been associated with FOG. Finally, the PDQ-39 will evaluate quality of life. 