|Institution:||University of Cincinnati|
|Department:||Medicine : Neuroscience/Medical Science Scholars Interdisiplinary|
|Keywords:||impulsivity; novelty processing; associative learning; bipolar disorder; cannabis; fMRI|
|Full text PDF:||http://rave.ohiolink.edu/etdc/view?acc_num=ucin1250679362|
Bipolar disorder (BD) is a major psychiatric illness that is characterized by fluctuations in mood states and often presents with co-morbid cannabis use disorders. Alterations in impulsivity and novelty processing are also common for individuals with BD. Novelty processing is important for detecting changes in the environment, while impulsivity is a normal part of human personality that allows for quick responses to these changes; together, these factors are essential for adaptation. We hypothesized that impulsivity and novelty processing are mediated by a common network of frontal cortico-limbic-striatal brain regions that are sensitive to modulation by psychiatric illness and substance abuse. In BD, this system of detecting change and responding appropriately may be altered and may represent susceptibility factors for abusing drugs. Despite evidence that cannabis use may contribute to the progression and etiology of symptoms, its affects on impulsivity and novelty processing during associative learning remain poorly understood. Therefore, we wanted to expand our understanding of the neuropathology and co-morbidity of bipolar disorder and cannabis use by (1) determining the neural correlates of novelty processing during associative learning and its associations with impulsivity in healthy individuals using functional magnetic resonance imaging (fMRI), and (2) by comparing differences in how cannabis use affects impulsivity and behavioral responsiveness to novelty in healthy and BD adolescents. Healthy adults exhibited widespread activation in frontal cortico-limbic-striatal regions in response to novel compared to familiar, or learned, events. Overall, novel stimuli elicited a much greater fMRI response than different types of novel feedback. We also found that scores on the Barratt Impulsiveness Scale (BIS) were positively correlated with the behavioral response to novel negative feedback, but negatively correlated with fMRI brain activation in response to novel stimuli. Furthermore, we found that cannabis use increased BIS scores and behavioral responsiveness to novel and unexpected negative feedback in both healthy and BD adolescents. However, drug naïve BD adolescents, compared with the other groups, exhibited an attenuated behavioral response to novel and unexpected negative feedback. Future neuroimaging studies are necessary to investigate the neural basis for altered novelty processing during associative learning in BD.