Inclusion Criteria:  Pain-free controls  TMD-Pain screener score less than 3 out of 7 (Screener available as part of the DC/TMD) No previous diagnosis for the most common pain-related TMD as defined in the DC/TMD criteria (myalgia, arthralgia, headache attributed to TMD) No significant orofacial pain (jaw pain, TMJ pain) in past 3 months ("significant" meaning 5 or more days in any month or any pain during the past month) No report of significant pain in the last 3 months elsewhere in the body ("significant" meaning 5 or more days in any month or any pain during the past month), e.g., low back pain, fibromyalgia, migraine headaches Not meeting any of the most common pain-related TMD diagnosis as described in the DC/TMD criteria (myalgia, arthralgia, headache attributed to TMD) upon clinical examination following the DC/TMD protocol  Chronic painful TMD cases  TMD-pain screener score equal to or greater than 3  Primary TMD caseness criteria: myalgia (masticatory muscle pain) based on clinical exam following the DC/TMD protocol  Concurrent arthralgia (TMJ pain) and/or headache attributed to TMD allowed  Myofascial pain must meet the following criteria:  Onset >3 months, occurring >15 days/month on average for >3 months Minimum 10 jaw pain episodes since onset, each episode lasting at least 30 minutes and no less than 2 hours within the day, OR unremitting Low-impact TMD pain cases: Graded Chronic Pain Scale (GCPS) grade IIa or lower High-impact TMD pain cases: GCPS grade IIb or greater  Exclusion Criteria:  Traumatic facial injury or surgery on the face/jaw, arms or hands Presence of pain related to dental or periodontal pathology Currently undergoing active orthodontic treatment Pregnant or nursing  Has any of the following medical conditions by self-report:  Renal failure or dialysis Heart disease (examples: uncontrolled arrhythmia or hypertension, cardiomyopathy) or heart failure Non-allergic bronchospasm (chronic obstructive pulmonary disease and emphysema) Diabetes (Type I or II) that is not controlled with medication or diet Hyperthyroidism Uncontrolled seizures  Used any injection therapy (i.e. tender or trigger point injections, steroid injections), acupuncture, biofeedback, or TENS for the management of facial pain within 2 weeks prior to the screening assessment  If undergoing botulinum toxin injections in the head and neck areas, must be 3 months since last set of injections and refrain from this treatment until study has ended History of major depression or other major psychiatric disorder requiring hospitalization within the last 6 months prior to the screening assessments History of treatment for drug or alcohol abuse within the last 12 months Current pain medication use (e.g. opioids, ibuprofen, acetaminophen) that cannot be stopped <24 hours prior to each study visit Other conditions/diseases associated with altered pain perception: neurological or developmental disorders (dementia, autism spectrum disorder), neoplasm, multiple sclerosis, trigeminal neuralgia MRA contraindications including claustrophobia GCPS grade assigned at Visit 1 that does not match grade from screening GCPS (low-, high-impact pain) and it is not possible to assign the potential participant to the correct final group, due to the latter having met their recruitment quota Strictly left-handedness by self-report Thermal threshold for Pain-50 (determined at Visit 1) is outside the temperature range of 40-49 degrees Celsius Lack of access to electronic device with internet connection during the study