http://www.jneurosci.org/content/33/4/1706.abstract
Abstract
Rewards in real life are rarely
received without incurring costs and successful reward harvesting often
involves weighing
and minimizing different types of costs. In the
natural environment, such costs often include the physical effort
required
to obtain rewards and potential risks attached
to them. Costs may also include potential risks. In this study, we
applied
fMRI to explore the neural coding of physical
effort costs as opposed to costs associated with risky rewards. Using an
incentive-compatible
valuation mechanism, we separately measured the
subjective costs associated with effortful and risky options. As
expected,
subjective costs of options increased with both
increasing effort and increasing risk. Despite the similar nature of
behavioral
discounting of effort and risk, distinct regions
of the brain coded these two cost types separately, with anterior
insula
primarily processing risk costs and midcingulate
and supplementary motor area (SMA) processing effort costs. To
investigate
integration of the two cost types, we also
presented participants with options that combined effortful and risky
elements.
We found that the frontal pole integrates effort
and risk costs through functional coupling with the SMA and insula. The
degree
to which the latter two regions influenced
frontal pole activity correlated with participant-specific behavioral
sensitivity
to effort and risk costs. These data support the
notion that, although physical effort costs may appear to be
behaviorally
similar to other types of costs, such as risk,
they are treated separately at the neural level and are integrated only
if
there is a need to do so.
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