Value Representations by Rank Order in a Distributed Network of Varying Context Dependency

We report the results of a human fMRI experiment investigating the influence of context upon value judgement. Trials were separated into high and low value blocks such that it is possible to investigate the effect of a change in surrounding trials upon the encoding of financial value. The ventral striatum was dependent upon "local context", with its activity representing the current stimulus' relative value compared only to items in the current block. Conversely the ventral medial Pre-Frontal Cortex and Anterior Cingulate Cortex respond independently of block but also do not represent the absolute values of stimuli. Our use of stimuli values with a non-linear distribution allow us to identify the pattern as representing rank order. This has wide reaching implications for research on neuroeconomics, decision making and reward representation, showing that financial value is not explicitly represented within the brain. (Contains 6 tables and 4 figures.)