Neural Correlates of Lidocaine Analgesia

Inclusion Criteria: * Adults aged 18 to 70 * Be of normal body-weight * Be generally healthy * Have none of the specific exclusion criteria * Have a valid email address and phone number throughout the study Exclusion Criteria: * Pregnancy * Body mass index \> 40 * Having moderate to severe sleep apnea * Having chronic pain requiring the regular use of pain medicine 3 or more times per week * Having neurologic or psychiatric disease, including benign tremor, anxiety, and depression * Having a history of seizures * Having history of cardiac rhythm disturbance (such as heart block, or atrial fibrillation) * Being severely claustrophobic * Having metal implants or non-removable metal piercings * Having metal-containing tattoos, particularly on the face * Having a history of adverse reaction to lidocaine * Are regularly taking: antiepileptics, antidepressants, anti-psychotics, anti-anxiety medication, stimulants, sleep-aids, or pain medication * Are taking prescribed medications for psychiatric or neurological conditions * Having hypersensitivity to lidocaine or to any other local anesthetics of the amide type * Having Wolff-Parkinson-White syndrome * Having known renal or hepatic dysfunction * having glucose-6-phosphate dehydrogenase deficiency or history of methemoglobinemia