Figure 1.

Signaling of outcome expectancies in the orbitofrontal cortex. Black bars show the response on trials involving the preferred outcome of the neurons in the post-criterion phase. White bars show the response to the non-preferred outcome. Activity is synchronized to odor onset and displayed in 100 ms bins; red boxes indicate the average duration of odor sampling and of the delay between responding and reinforcement when a response was made at the fluid well. (a) The average response of neurons that responded selectively during a delay period early in learning, after the rat went to the fluid well but before delivery of one of the outcomes (Pre). This activity signals the expected outcome after responding. (b) Later (Post), these neurons became activated by the odor cue that predicted the preferred outcomes of the neurons after learning, thereby signaling the expected outcome at the time the decision to respond is made. (c) This pattern switched after reversal of the odor–outcome associations (Rev). Average firing rate is shown on the y-axis in spikes per second. Adapted, with permission, from [13].