Neural Mechanisms of Cost and Benefit Integration During Decision-Making, Aim 2: Acute & Lifetime Stress

Neural Mechanisms of Cost and Benefit Integration During Decision-Making, Aim 2: Acute & Lifetime Stress

The central aim of this study is to characterize how the costs of acute and lifetime stress affect the neural architecture for decision-making in healthy humans. Investigators will use behavioral choice paradigms to measure how the costs of stress influence decisions about rewards (e.g., foods, money) as well as decisions about the use of self-control strategies. They will further examine associations between these stress measures and other decision variables commonly studied in our lab which have well-understood mechanisms, such as risk preferences. This behavioral work lays the foundation for an fMRI experiment that combines our measures of the behavioral costs of stress with neural measures of brain changes. Acute stress will be measured using a physiological stressor (cold-pressor task) coupled with saliva sample collection for cortisol analysis. Lifetime stress will be measured using a computerized life stress survey. We will study three cohorts: One purely behavioral cohort will be examined on-site (n=60). In a smaller subset of participants (n=40), investigators will measure neural activity changes in relevant brain areas as measured with MRI during decisions to use self-control in the presence of rewards. In a larger sample (n=500) the correlation between participants' risk preferences and lifetime stress exposure at scale using Amazon Mechanical Turk subjects will be measured.

Inclusion Criteria:

• English as a native language
• Corrected-to-normal vision
• Individuals on diets to maintain or lose weight, or those not on a diet
• All races, ethnicities, and cultures

Exclusion Criteria:

• For all fMRI studies we will exclude participants who meet one of the standard CBI MRI exclusion criteria (see attached exclusion questionnaire) prior to participation. This screening questionnaire will be administered prior to scheduling the study, and once again before the scanner session during the second consenting procedure.
• History of and/or medication for neurological or psychiatric disorders
• High blood pressure, heart condition or related medical conditions
• Diabetes, metabolic disorders, history of eating disorders, or food allergies
• Pregnancy
• Handedness (this has been shown be indicative of variations in brain circuitry)
• Since we will measure stress hormones, subjects currently taking corticosteroids or beta-blockers will be ineligible to participate, as these medications have been found to dramatically alter stress hormone levels.
• Furthermore, evidence suggests that fluctuations in bodily hormones (such as that induced through hormonal contraceptives or different stages of menstrual cycle phase) can affect stress hormone levels (Tersman, Collins, & Eneroth, 1991; Kirschbaum et al, 1999; Andreano, Arjomanid, Cahill, 2008). In order to account for hormonal differences, we will ask female participants if they are taking oral contraceptives. Likewise, we propose to use a simple, non-invasive questionnaire to determine cycle phase, as in McCormick & Teillon, 2001. We may need to exclude on the basis of whether or not female participants use hormone-based contraceptives, which, for the reason stated above, could be a potential confound.
• In some cases, we will pre-screen subjects to ensure they are on a diet to maintain or lose weight in order to examine how dietary and health goals influence decisions about self-control and rewards.