Neuroanatomical correlates of approach-avoidance conflict (fMRI)

Description: Neuroanatomical correlates of approach-avoidance conflict (fMRI)

Please cite the following reference if you use these data:

Zorowitz S, Rockhill AP, Ellard KK, Link K, Herrington T, Pizzagalli DA, Widge AS, Deckersbach T, Dougherty DD (2019) The Neural Basis of Decision Conflict: A Model Based Analysis. eNeuro, Submitted.

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We employed a modified version of the Aversion-Reward Conflict (ARC) task (Sierra-Mercado et al., 2014). During this task, participants make a series of choices between two options: a safe option or a risky option. Selecting the safe option returns a monetary reward of $0.01 and never electrical stimulation. In contrast, selecting the risky option returns a monetary reward between $0.05 and $0.95, and electrical stimulation with probability 10%, 50% or 90%, as indicated by a bar in the center of the screen. This required participants to evaluate their preference for more reward and risk of shock relative to smaller reward and no risk of shock. Participants were instructed to choose as fast as possible without choosing randomly, and were informed that their choices would be reflected in their final study payment. Prior to starting the task, participants were asked to report back the instructions so that their comprehension could be verified. After, they completed ten practice trials to become accustomed to the timing of the task.

The ARC task has three levels of risk: 10%, 50%, and 90% likelihood of shock. Rewards ranged continuously between $0.05 and $0.95. Trials were counterbalanced such that there were an equal number of trials at each risk level, and such that monetary rewards were uniformly and equally sampled within each risk level. Each participant completed 108 total trials and the order of trials was kept constant for all the participants. Long inter-trial intervals of 10.5 ± 0.875 seconds separated sequential trials in the task (yielding a slow event-related design). The duration of the full task was 28.5 minutes.

Electrical stimulation was administered to the ankle through a Coulbourn Aversive Finger Stimulator (Harvard Apparatus, E13-22; maximum level of stimulation = 4.0 mA). The amperage of electrical stimulation was calibrated individually for each participant prior to performing the ARC task. Participants experienced increasing levels of stimulation until they reported reaching a subjective threshold qualified as “highly annoying but not painful”. For five participants this threshold could not be established because the highest stimulation setting of 4.0 mA was too painful, but penultimate 2.3 mA setting was not experienced as annoying. These participants did not exhibit behavioral variation (i.e., they always accepted the risky choice).