Karmen Yoder, PhD
Dr. Yoder is assistant professor of radiology in research and imaging sciences at the Indiana University School of Medicine. She is also associate investigator in the Stark Neuroscience Research Institute at the IU School of Medicine.
Dr. Yoder's interests are in the area of in vivo neurochemistry of CNS disorders and cognition using positron emission tomography, or PET.
Dr. Yoder focuses on using quantitative PET techniques to study in vivo neurochemical processes in humans and in animal models of abnormal brain function. Tracers of interest include [11C]raclopride (dopamine D2 antagonist used to study striatal dopamine function), [18F]fallypride (DA D2 antagonist, permits study of extrastriatal DA systems), [11C]PIB (marker for amyloid deposition), and [11C]DAA1106 (binds to the peripheral benzodiazepine receptor, a marker of neuroinflammation).
Dr. Yoder and her collaborators were the first to directly demonstrate that human striatal dopamine (DA) levels change during positive and negative prediction error conditions, confirming previous electrophysiology studies in animals. They have also shown that cognitive state affects striatal DA D2 receptor availability. Recently published work described a method for quantitating alchohol-induced changes in DA levels that does not require subjects to have anatomically identical responses. Dr. Yoder has extramural and intramural funding for several projects, which include: determination of the test-retest reliability of a spatially independent method for quantitating human striatal DA responses to alcohol; evaluating the extrastriatal DA system in alcoholics; and assessing the extrastriatal DA response to motor and cognitive tasks in healthy humans.
Additional pilot studies will compare striatal DA tone between chronic cannabis users and healthy controls, and will examine if naltrexone (a drug used to treat alcoholism) affects the DA system in alcoholics. Upcoming studies will characterize the DA response to negative prediction error in social drinkers and alcoholics, test the effects of naltrexone on DA prediction error response in alcoholics, and assess the DA system in fibromyalgia. Dr. Yoder works closely with Dr. E. Morris on development of methods that will recover the temporal dynamics of neurotransmitter release using PET (ntPET), and with Dr. D. Kareken, who studies DA with respect to sensory cues involved in addictive processes.
Dr. Yoder is also helping to develop several collaborative projects within the Center for Neuroimaging, including: determining the role of DA in metacognition in schizotypal syndromes; discerning the roles of neuroinflammation and amyloid deposition in traumatic brain injury (TBI) in humans and in animal models of TBI; and development of small animal PET imaging paradigms to longitudinally assess neuroinflammation and amyloid deposition in transgenic mouse models of neurodegenerative disorders.