Carbon Dioxide Administration and Brain Waste Clearance

Inclusion criteria for TBI cohort: 1) Able to give valid informed consent, 2) 18-82 years old, 3) history of TBI of any severity level (mild, moderate or severe) that was sustained in adulthood (age 18 and older), which will be confirmed using a semi-structured identification method (includes asking about loss of consciousness, posttraumatic amnesia, and feeling dazed/confused). Inclusion criteria for Healthy Subjects cohort: 1) Able to give valid informed consent and 2) 18-82 years old years old. Exclusion criteria for TBI cohort: 1) contraindications to MRI scanning including pregnancy or claustrophobia, 2) unable to give valid informed consent, incarcerated, 3) diagnosed with Alzheimer's, ADRD or mild cognitive impairment, 4) pre-existing history of autism spectrum disorders, intellectual disability, serious neurological (e.g., epilepsy, tumors, other conditions requiring neurosurgery) or psychiatric disorders (requiring hospitalization) prior to TBI onset, 5) current or previous diagnosis of a psychosis spectrum disorder or bipolar disorder, 6) respiratory diseases or pulmonary conditions that may increase the risk of study procedures (e.g., severe asthma, chronic obstructive pulmonary disease or other significant respiratory disorders), 7) a history of cardiac arrythmias 8) history of a current substance use disorder, 9) non-English fluency (based on screener), 10) Weigh under 110 pounds for blood draw. Exclusion criteria for Healthy Subjects cohort: 1) contraindications to MRI scanning including pregnancy or claustrophobia, 2) unable to give valid informed consent, incarcerated, 3) diagnosed with Alzheimer's, ADRD or mild cognitive impairment, 4) history of developmental, neurological, or psychiatric disorders requiring hospitalization, 5) regular use of any substance in the past six months (i.e., no current use confirmed with urine screening), 6) previous head injury with greater than 30 minutes loss of consciousness, 7) respiratory diseases or pulmonary conditions that may increase the risk of study procedures (e.g., severe asthma, chronic obstructive pulmonary disease or other significant respiratory disorders), 8) a history of cardiac arrythmias, 9) non-English fluency (based on screener), 10) Weigh under 110 pounds for blood draw.