ACHE and Parkinson disease: For example, although cholinergic augmentation with acetylcholinesterase inhibitors can improve gait and turning in PD,36,37 their side effects are burdensome and particularly problematic in the older adult population.30 Therefore, alternative treatment options to increase cholinergic function need to be investigated, including exercise, vagus nerve stimulation, transcranial direct current stimulation (tDCS), and others.