Specificity of Flavor-Nutrient Learning: An fMRI Experiment

The primary objective of the behavioral impulsivity task was to examine motor disinhibition as represented by response time to the beverage logos and control logos. Participants were instructed to respond as quickly and accurately as possible with a keyboard press when shown the target logo, but withhold their responses during presentation of other logos. Participants performed the task twice, each time depicting one of the beverage logos as the 'target' logo at both the pre- and post-intervention assessments. The order of which logo was the 'target' logo was in a counterbalanced. Each task consisted of 48 trials. Stimuli were presented and reaction times, commission and omission errors were recorded using the Presentation software package (Version 9, Neurobehavioral Systems, Davis, CA). Change in response time is calculated as a difference between baseline and post-intervention assessment average response time across 48 trials.

The secondary objective of the behavioral impulsivity task was to examine error rate in response to the beverage logos and control logos. Participants were instructed to respond as quickly and accurately as possible with a keyboard press when shown the target logo, but withhold their responses during presentation of other logos. Participants performed the task twice, each time depicting one of the beverage logos as the 'target' logo at both the pre- and post-intervention assessments. The order of which logo was the 'target' logo was in a counterbalanced. Each task consisted of 48 trials. Stimuli were presented and reaction times, commission and omission errors were recorded using the Presentation software package (Version 9, Neurobehavioral Systems, Davis, CA). Change in error rate is calculated as a difference between baseline and post-intervention assessment total number of commission and omission error across 48 trials.

All visual analog scales were presented on a computer screen and completed one at a time. If the scale was assessing response to taste, the participant consumed a small amount of the beverage and completed the associated scales. Perceived pleasantness of, and desire to consume the two juices was measured using adapted labeled hedonic scales at pre-/post-intervention. Pleasantness was phrased 'How pleasant is this taste' and anchored by (-100) 'most unpleasant imaginable' to (100) 'most pleasant imaginable', and 'neutral' (0) in the middle. Desire followed a similar pattern using 'desire to consume' as the phrasing. Pleasantness and desire of the assigned juice was also evaluated at the 9 intervention assessments. Perceived hunger was assessed via cross-modal visual analog scales, anchored by (-100) 'I am not hungry at all' to (100) 'I have never been more hungry'. The change score was calculated from the slope of ratings plotted by time.

The Dutch Eating Behavior Questionnaire is a 33-item self-report measure designed to assess the type of eating behavior and is organized into 3 subscales (emotional eating, externally-induced eating, and restrained eating). Subjects rated the frequency of their eating behaviors using a 5-point scale, where 1=never, 2=seldom, 3=sometimes, 4=often, and 5=very often. The Restrained Eating subscale consisted of 10 items and the scores ranged from 10 (worse outcome) to 50 (better outcome). The change was calculated as the difference between scores at Baseline and Post-Intervention Assessment.

The Food Frequency Questionnaire (FFQ) is a self-reported checklist of 76 foods and beverages with a frequency response section. Subjects report generally how often each item was consumed over a two-week period of time. The six possible responses are 1= never in the last two weeks, 2= 1-3 times in the last 2 weeks, 3= 4-6 times in the last 2 weeks, 4= 7-9 times in the last two weeks, 5= 10-13 times in the last 2 weeks, 6= daily or more in the last two weeks. Responses information is used to estimate daily caloric intake (number of kcal) and macronutrient content (percent calories from carbohydrate/fat/protein). Food pattern is assessed as an aggregate of these measures. Changes in food pattern will be assessed as a difference from baseline to post-intervention assessment.

The Food Craving Inventory is a 28-item instrument measuring the frequency over the past month of general cravings and cravings for specific types of foods, namely: high fats, sweets, carbohydrates/starches, and fast-food fats. Subjects rate how often they have experienced a craving for each food on a 5-point frequency scale, where 1=never, 2=rarely (once or twice), 3=sometimes, 4= often, 5= always/almost every day. Food craving score is calculated as a total sum, and the change score is calculated from the difference between baseline to post-intervention assessment.

The Power of Food scale assesses reported appetitive drive, food reward responsivity, sensitivity to food cues in the environment, and the frequency of food-related thoughts. The 21-item scale prompts subjects to rate how much they agree with statements about hedonic hunger on a 5-point scale, where 1=do not agree at all, 2=agree a little, 3=agree somewhat, 4=agree, and 5=strongly agree. The change in total PFS score will be calculated from the difference between baseline to post-intervention assessment.

The Yale Food Addiction Scale (YFAS) was designed to identify participants who exhibit signs of possible food addiction to specific foods. The 9-item questionnaire is based on substance dependence criteria in the DSM-IV-TR, as well as on scales that have been used to assess behavioral addictions. Subjects rate how often they have experienced a possible food addictive behavior on a 5-point frequency scale, where 0=never, 1=once a month, 2=2-4 times per month, 3= 2-3 times per week, 4= 4+ times per week. The change in total score is calculated from the difference between baseline to post-intervention assessment.