fMRI Studies of Working Memory and Motivation
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DESCRIPTION (provided by applicant): This proposal focuses on the way reward and motivation are linked to executive function. Reward representation and working memory are key functions of the prefrontal cortex (RFC), but their interactions are not well understood at the neural systems level. This line of functional MRI experiments will test fundamental assumptions about the way motivation and performance are represented in the brain. All experiments use variations of a working memory task requiring the maintenance of faces or scenes that has been shown to recruit PFC and posterior visual areas (Parahippocampal Place Area and Fusiform Face Area). Further, the task allows for the separation of working memory component processes involved in encoding, maintenance, and response. Experiment 1 will test whether manipulations of reward value recruit separable, or additional PFC regions and whether modulations in posterior visual areas can be altered by higher motivation trials. A second experiment will investigate financial penalty trials to assess the differences that may exist in a non- rewarded motivation manipulation. There are several theoretical reasons that reward and penalty activation may differ in important ways and these have not been previously tested using cognitive working memory paradigms. Analyses will include whole-brain, ROI, and correlational approaches to assess the activation differences based on varying reward motivation in the task. We hypothesize that activation within encoding, maintenance, and response related regions will be modulated by varying degrees of task motivation based on reward and punishment respectively. We will also include a modified task that will allow for superior modeling of the task periods by using partial trial methodology. This will allow us to test for timing differences in activation between PFC and posterior visual regions at different task phases. Overall, this research will clarify the functional organization of working memory and motivation. The generation of knowledge about reward and cognition has great clinical relevance for understanding the motivational properties of addictive stimuli such as substances of abuse and may also provide insight into a wide range of neurological disorders such as closed head injury, stroke and dementia that cause PFC dysfunction.
