People in all walks of life routinely make choices between pairs of goods or alternatives. Such choices range from deciding between movies to whether to resign in the face of impeachment. Such choices may range from home financing to following and/or investing in the New York Stock Exchange. We plan to differentiate neuronal activity of the brain on stylized versions of the paired choice task. But why focus on the brain? Certainly there is the inherent feeling that simply making the exploration may tell us something in light of the immense ground that has been broken in neurology in recent years. Given the improved understanding of depression, Parkinson's syndrome and bulimia there is every reason to believe that the study of neuronal activity will give us an improved understanding of normal everyday choice, along dimensions where there still remain many unanswered questions. But more specifically we wish to focus on individual choices that are fundamentally economic. Why? We see a need to more completely specify the individual choice process so as to get arrive at an understanding of the price formation process. Recently it has become possible to delineate the price formation process of the double auction by revising models of individual choice. Similarly it has become possible to isolate systematic preconscious processing behavior in the performance of simple economies such as the English Auction. To come to the point that one can fully articulate what will happen across a large vista of economic phenomena using revised models of individual choice we need to begin to supply information on what is happening in the simplest of environments, the paired choice task. In the paired choice task, we will study 2 basic questions. First we ask, `Does the pattern of neuronal activity in response in a fixed choice paradigm change with the introduction of risk, and again of ambiguity?` Then we ask, `Is there a differential pattern of neuronal activity in response to gains and losses? Is the pattern of neuronal activity in response to a fixed choice paradigm more complex (as specified below) for losses than gains?` We anticipate much more parahippocampal involvement in the processing of risk and uncertainty than in the other tasks. Differential amygdala and orbital frontal activation is expected with losses versus gains. Furthermore, there is a strong likelihood that affective processes mediated by the limbic and paralimbic cortices will produce increasing levels of neuronal activity in the ventralmedial orbitalfrontal cortex as task conditions change from certainty to risk to ambiguity. It is expected that medial orbital frontal cortex will play a modulating role with respect to episodic memory's impact on the unconscious mechanisms active during choice under risk and ambiguity and participate with the amygdala in the effects of emotional arousal on memory. Our project uses PET to measure brain blood flow, an established marker of neuronal activity. Twenty right-handed normal subjects will participate in the task. Stimulus delivery and response acquisition will be generated using MEL v2.0. In addition, GSR and Heart Rate Monitors will be used to provide cross validation of PET inferences. The PET scanner is a Siemens ECAT 953B camera, while data are analyzed with SPM 96. The research will contribute fundamentally to our understanding of the neuronal processes that support the interplay of cognitive and affective information processing during the choice task. In particular, the coupling of PET methodology and the paired choice paradigm promises to distinguish differential neuronal activity that may be triggered by risk and ambiguity and by gains and losses.
