The decision to engage cognitive control is driven by expected reward-value: neural and behavioral evidence

Abstract

Cognitive control is a fundamental skill reflecting the active use of task-rules to guide behavior and suppress inappropriate automatic responses. Prior work has traditionally used paradigms in which subjects are told when to engage cognitive control. Thus, surprisingly little is known about the factors that influence individuals' initial decision of whether or not to act in a reflective, rule-based manner. To examine this, we took three classic cognitive control tasks (Stroop, Wisconsin Card Sorting Task, Go/No-Go task) and created novel 'free-choice' versions in which human subjects were free to select an automatic, pre-potent action, or an action requiring rule-based cognitive control, and earned varying amounts of money based on their choices. Our findings demonstrated that subjects' decision to engage cognitive control was driven by an explicit representation of monetary rewards expected to be obtained from rule-use. Subjects rarely engaged cognitive control when the expected outcome was of equal or lesser value as compared to the value of the automatic response, but frequently engaged cognitive control when it was expected to yield a larger monetary outcome. Additionally, we exploited fMRI-adaptation to show that the lateral prefrontal cortex (LPFC) represents associations between rules and expected reward outcomes. Together, these findings suggest that individuals are more likely to act in a reflective, rule-based manner when they expect that it will result in a desired outcome. Thus, choosing to exert cognitive control is not simply a matter of reason and willpower, but rather, conforms to standard mechanisms of value-based decision making. Finally, in contrast to current models of LPFC function, our results suggest that the LPFC plays a direct role in representing motivational incentives.

Figure 1. Behavioral Results.

Percentage (%) of choices in which cognitive control was selected during the free-choice period as a function of expected monetary rewards. Error bars represent one (within-subject) standard error of the mean based on Loftus and Masson .

Figure 2. Trial Structure for the fMRI Experiment.

After a variable duration fixation cross, an instruction cue signaled the currently relevant rules (profile of faces = male/female rule; book = abstract/concrete rule) and whether or not to expect a monetary reward (blue vase = no money; bills = 25¢). This was followed by a variable duration delay period and then a word or face stimulus, during which subjects made a button response. Finally, a screen revealed whether money had been earned on that trial and cumulative winnings. On key trials, a second instruction cue appeared before the stimulus. Across the two instruction cues, we varied whether there was repetition of the rules, expected reward, both, or neither.

Figure 3. Regions Showing Repetition Enhancement for Repetition of a Specific Rule-Outcome Pairing (Z>2.57, p<.05 FWE cluster corrected for the whole-brain).

A. Right lateral view showing regions of the LPFC exhibiting this effect. B. Activation time-course for the IFS, IFJ, and posterior DLPFC time-locked to the onset of the second instruction. The color scale denotes t-values. Nov = novel, rep = repeated. Error bars represent one (within-subject) standard error of the mean based on Loftus and Masson .

Figure 4. Regions Exhibiting Functional Connectivity with the IFS Across the Entire Time-Course (Z>2.57, p<.05 FWE cluster corrected for the whole-brain).

Rule areas (blue arrows) include bilateral lateral prefrontal cortex (LPFC), anterior mid-cingulate cortex/dorsomedial prefrontal cortex (aMCC/DMPFC), posterior middle temporal gyrus (pMTG), and intraparietal sulcus (IPS). Reward areas (red arrows) include rostral anterior and posterior cingulate cortices (rACC, PCC), orbitofrontal cortex (OFC), caudate/nucleus accumbens (NAcc), and insula. The color scale denotes t-values, and the numerical values above the images correspond to MNI coordinates. For axial and coronal slices, the right hemisphere is on the right side of the image. LH = left hemisphere, RH = right hemisphere.