Free choice shapes
normalized value signals in medial orbitofrontal cortex
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Yamada H, Louie K, Tymula A,
Glimcher PW
Nat Commun, 9 (2018) |
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Normalization
is a common cortical computation widely observed in sensory perception,
but its importance in perception of reward value and decision making
remains largely unknown. We examined (1) whether normalized value
signals occur in the orbitofrontal cortex (OFC) and (2) whether changes
in behavioral task context influence the normalized representation of
value. We record medial OFC (mOFC) single neuron activity in
awake-behaving monkeys during a reward-guided lottery task. mOFC
neurons signal the relative values of options via a divisive
normalization function when animals freely choose between alternatives.
The normalization model, however, performed poorly in a variant of the
task where only one of the two possible choice options yields a reward
and the other was certain not to yield a reward (so called: “forced
choice”). The existence of such context-specific value normalization
may suggest that the mOFC contributes valuation signals critical for
economic decision making when meaningful alternative options are
available.
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