Encoding of time-discounted rewards in orbitofrontal cortex is independent of value representation

Neuron. 2006 Aug 17;51(4):509-20. doi: 10.1016/j.neuron.2006.06.027.


We monitored single-neuron activity in the orbitofrontal cortex of rats performing a time-discounting task in which the spatial location of the reward predicted whether the delay preceding reward delivery would be short or long. We found that rewards delivered after a short delay elicited a stronger neuronal response than those delivered after a long delay in most neurons. Activity in these neurons was not influenced by reward size when delays were held constant. This was also true for a minority of neurons that exhibited sustained increases in firing in anticipation of delayed reward. Thus, encoding of time-discounted rewards in orbitofrontal cortex is independent of the encoding of absolute reward value. These results are contrary to the proposal that orbitofrontal neurons signal the value of delayed rewards in a common currency and instead suggest alternative proposals for the role this region plays in guiding responses for delayed versus immediate rewards.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Action Potentials / physiology
  • Animals
  • Behavior, Animal
  • Brain Mapping
  • Choice Behavior
  • Discrimination Learning / physiology
  • Frontal Lobe / cytology
  • Frontal Lobe / physiology*
  • Male
  • Neurons / classification
  • Neurons / physiology*
  • Probability
  • Rats
  • Rats, Long-Evans
  • Reaction Time / physiology
  • Regression Analysis
  • Reward*
  • Space Perception / physiology*
  • Time Factors