Could a head zapper and gentle yoga ease knee pain in dementia?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria (participants): * Live in the community (not institutionalized). * Have a diagnosis of Alzheimer's disease and related dementias (ADRD), including Alzheimer's disease, Lewy Body Dementia, Vascular Dementia, or Multiple Etiology Dementias (MED) diagnosed by a neurologist or other healthcare provider. * Be in mild to moderate ADRD, as indicated by a Quick Dementia Rating Scale (QDRS) score between 6 and 20.5. * Score above 10 on the Montreal Cognitive Assessment (MoCA). * Experience chronic knee pain (caregiver-reported average pain in the past 3 months \> 40 out of 100). * Have no planned changes to their medication regimen or other interventions for knee pain during the trial. * Agree to participate in both transcranial direct current stimulation (tDCS) and online chair yoga (OCY). * Be able to ambulate independently with minimal assistance (e.g., using a cane or walker) for participation in OCY and the Timed Up and Go (TUG) test. - -- Be English-speaking and able to understand verbal instructions (literacy not required). * Be able to consent for themselves or identify a legally authorized representative who can provide written informed consent. * Exhibit neuropsychiatric symptoms (e.g., apathy, agitation). * Be naïve to yoga and tDCS. Exclusion Criteria (participants): * a history of brain surgery, brain tumor, head trauma, seizure/epilepsy, stroke, cancer affecting the head, or intracranial metal implantation; * systemic rheumatic disorders, including rheumatoid arthritis, systemic lupus erythematosus, or fibromyalgia; * prosthetic knee replacement or non-arthroscopic surgery to the affected knee; * compromised skin integrity on the head in the area where electrodes will be placed; * serious comorbidities that preclude participation in tDCS or OCY (e.g., heart failure \[level IV\] causing shortness of breath on exertion); * hospitalization within the preceding year for neuropsychiatric illness that would impact knee pain or interfere with study procedures; * use of another neurostimulation device (e.g., spinal cord stimulator, cardio-stimulator, or implanted cardioverter-defibrillator). Inclusion Criteria (caregivers): A caregiver is defined in this study as the person who provides care and assistance to a patient with ADRD (e.g., helping with daily activities, managing medications, ensuring safety). * Caregivers must be at least 18 years old * have provided care and assistance to the patient for at least 10 hours per week at the time of enrollment * anticipate continuing to provide care and assistance for the next 4 months (until the study ends) * be willing to receive tDCS training, administer home-based tDCS sessions, and assist the patient in attending OCY sessions * have access to a reliable Internet connec¬tion for secure videoconferencing for real-time remote supervision * English-speaking caregivers who can understand verbal instructions. Exclusion Criteria (caregivers): * alcohol/substance use disorder * inability to understand English * disability that would prevent assisting patients with ADRD from participating in tDCS and OCY (e.g., blindness, deafness) * unwillingness to provide care and assistance to patients until the study is completed. * If caregiver does not meet the inclusion/exclusion criteria, the participant will not be accepted into the study.