To survive in a dynamic
environment, an organism must be able to effectively learn, store, and
recall the expected benefits and costs of potential actions. The nature
of the valuation and decision processes is thus of fundamental interest
to researchers at the intersection of psychology, neuroscience, and
economics. Although normative theories of choice have outlined the
theoretical structure of these valuations, recent experiments have
begun to reveal how value is instantiated in the activity of neurons
and neural circuits. Here, we review the various forms of value coding
that have been observed in different brain systems and examine the
implications of these value representations for both neural circuits
and behavior. In particular, we focus on emerging evidence that value
coding in a number of brain areas is context dependent, varying as a
function of both the current choice set and previously experienced
values. Similar contextual modulation occurs widely in the sensory
system, and efficient coding principles derived in the sensory domain
suggest a new framework for understanding the neural coding of value.
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