Inclusion Criteria:  Bilateral STN DBS for PD Medtronic Percept PC implanted DBS battery/pulse generator/recording system Presence of balance and/or walking impairment and/or freezing of gait Can walk without assistance, OFF meds, based on yes/no verbal response  Exclusion Criteria:  Severity of gait impairment should not require dependency to walker or cane Cannot tolerate monopolar stimulation at either of the two middle electrode contacts (prerequisite for the recording mode of the DBS) at high frequency (130 Hz) or low frequency (60 Hz). Concomitant conditions that may affect significantly the evaluation of balance or gait, including orthopedic, rheumatologic or other neurological diseases Contraindication to physical therapy Age < 21 Diagnosis of dementia Not agreeable to having video taken of entire research visit