The neural basis of predicting the outcomes of imagined actions

Abstract

A key feature of human intelligence is the ability to predict the outcomes of one's own actions prior to executing them. Action values are thought to be represented in part in the dorsal and ventral medial prefrontal cortex (mPFC), yet current studies have focused on the value of executed actions rather than the anticipated value of a planned action. Thus, little is known about the neural basis of how individuals think (or fail to think) about their actions and the potential consequences before they act. We scanned individuals with fMRI while they thought about performing actions that they knew would likely be rewarded or unrewarded. Here we show that merely imagining an unrewarded action, as opposed to imagining a rewarded action, increases activity in the dorsal anterior cingulate cortex, independently of subsequent actions. This activity overlaps with regions that respond to actual unrewarded actions. The findings show a distinct network that signals the prospective outcomes of one's possible actions. A number of clinical disorders such as schizophrenia and drug abuse involve a failure to take the potential consequences of an action into account prior to acting. Our results thus suggest how dysfunctions of the mPFC may contribute to such failures.

Keywords: action values; anterior cingulate cortex; cognitive control; prospection.

Figure 1

Imagine condition. In the Imagine condition, participants saw a sequence of two arrows, one facing left and the other facing right (order randomized across trials). As each arrow appeared, participants were instructed to imagine performing the corresponding button press response (left or right) and the outcome associated with it. An exclamation mark (“!”) cued the subjects to make a response of their choice. One of the two options was rewarded action, and the other would be unrewarded action. The rewarded action response in the preceding trial was more likely to be rewarded action in the current trial. Participants received either rewarded (“$”) or non-rewarded (“0”) feedback as a result of their choice. The response cue and outcome cues were identical to the Imagine condition.

Figure 2

Red: regions showing increased activation in response to imagining a non-rewarded action contrasted with imagining a rewarded action response, depicted at p < 0.01, uncorrected. Green: areas showing greater activation for non-rewarding feedback contrasted with rewarding feedback, depicted at p < 0.001, uncorrected. Yellow: regions common to both contrasts.

Figure 3

Parameter estimates extracted from left and right motor cortex for Imagining Rewarded and Imagining Non-Rewarded outcomes associated with left and right button presses. ImagineL, ImagineLeft; ImagineR, ImagineRight.