The Neural Competition Of Dual-system Process In Ratio-bias Effect

The "ratio-bias effect" refers to that same probability is experienced as larger if itcomes as a ratio of two larger numbers (eg.1/10and10/100). Previous studiescontributed this phenomenon to the existence of analytical-rational andintuitive-experiential processing systems within models of human choice that is thedual-process theory, but its neural basis is still unclear. Using functional magneticresonance imaging (fMRI) based task we found the subjects with stronger ratio-biaseffect showed more activated in brain areas related both intuitive(the right insula),analytical processing (the right dsolateral prefrontal cortex (rDLPFC)), suggesting thekey role of the two different system in ratio-bias. Moreover, the varied activity of MCCboth across subjects and task demonstrated the conflict between two systems fromneural perspective.This paper mainly focused on the study of dual-system process in ratio bias effectbased on functional magnetic resonance imaging (fMRI). Using functional magneticresonance imaging (fMRI) based task, we analyzed the brain activation of subjects withstrong and low ratio-bias effect, when performing conflict and non-conflict task. Inaddition, Psychophysiological interaction (PPI) was applied to explore the functionalconnectivity of dual-system in ratio-bias effect. Some aspects of this dissertation havebeen put forward:1. Study of the brain activation. The subjects with stronger ratio-bias effect showedmore activated in brain areas related both intuitive (the right insula), analyticalprocessing (the right dsolateral prefrontal cortex (rDLPFC)), suggesting the key role ofthe two different system in ratio-bias. Moreover, the varied activity of MCC both acrosssubjects and task demonstrated the conflict between two systems from neuralperspective.2. Study of the connectivity of brain. The right insula and the rDLPFC were foundpositively interacted during the ratio-bias task, which was consist with the brainactivation results. Besides, PPI analysis with the ACC as the seed area showedconnectivity between the ACC and the frontal and this connectivity was related to competition. This result might reveal that the functional connectivity between the ACCand the frontal played a key role in dual-system competition. Thus, the interaction andcompetition mechanism of the two systems were further demonstrated by functionalconnectivity analysis.