openneurodatasets / ds000229 Goto Github PK

Data acquisition methods have been described in detail in Veldhuizen et al. (under revision) xxx and de Araujo, I. E., Lin, T., Veldhuizen, M. G. & Small, D. M. Metabolic regulation of brain response to food cues. Current biology : CB 23, 878-883, doi:10.1016/j.cub.2013.04.001 (2013).

Subjects
Fifteen healthy weight right-handed subjects (seven female, mean age 23.9 ± standard deviation (sd) of 3.5 years, mean body mass index (BMI) 22.4 ± 1.4 kg/m2, range 19.2-24.4 kg/m2) consented to our study that was approved by Yale University School of Medicine Human Investigation Committee. All subjects reported having no known taste, smell, neurological, or psychiatric disorders. 

Pre-Conditioning Session
Stimuli
Stimuli were ten differently flavored non-caloric beverages, contained 0.1% (w/v) citric and 0.0078% sucralose (Sigma-Aldrich Inc. MO, USA) dissolved in demineralized water. The beverages also each had a flavor and a color that were assigned in a counterbalanced manner prior to the pretest, such that there was no consistent flavor-color pairing across subjects (flavor-color pairing was kept constant for each subject across sessions). The flavors used were 0.002% acerola, 0.5% bilberry, 0.1% horchata, 0.1% lulo, 0.2% yuzu. 0.1% papaya, 0.1% chamomile, 0.1% aloe vera, 0.1% mamey, and 0.2% maqui berry (Bell Labs Flavors and Fragrances Inc., IL, USA, product numbers: 33.81940, 15.80182, 132.81478, 141.14606. 101.29478, 102.82506, 141.31243, 141.31480, 46.29969 and 13.32059). The flavors are relatively novel and absent of gustatory or trigeminal components. Food coloring (McCormick & Co, Inc., MD, USA) was used to make the beverages pink, yellow, green, blue, purple, red, orange, teal, yellow-green or indigo. Pilot testing with the in-lab formulated beverages showed that they were near neutral and similarly liked (data not shown). For the maltodextrin triangle test we randomly selected a SoBe lifewater (“mango melon”, “black and blueberry”, “yumberry pomegranate”, “acai fruit punch” or “Fuji apple pear” from PepsiCo, NY, USA) that contained <5 calories. The lifewater was mixed with maltodextrin (Spectrum, CA, USA) at 34% (w/v), equivalent to 150 calories in 355 ml. Since water activates taste cortex  (Frey and Petrides 1999, Zald and Pardo 2000) and has a taste (Bartoshuk, McBurney et al. 1964), we used “artificial saliva” as a flavorless control stimulus and rinse for the fMRI scan (Veldhuizen, Bender et al. 2007). Stimuli in the pretest phase were all presented as 10 ml aliquots in 30 ml medicine cups. Demineralized water was available for rinsing between stimuli.
Procedure
Subjects were instructed not to eat or drink anything except water for four hours prior to each session since conditioning has been shown to be stronger when hungry (Mobini, Chambers et al. 2007).  Upon arrival we used a Q-tip to swab the subject’s cheek and told them that this would allow us to detect whether she/he had fasted as instructed. These samples were not actually assayed, but were intended to encourage compliance. Each subject was asked to indicate her/his internal state by rating how hungry, full, and thirsty she/he was, on VAS scales that recorded responses from 0 (e.g. “Not Hungry At all”) to 100 (e.g. “Very Hungry”), a recurring set of ratings that we will refer to as “internal state ratings” from here on. The control solution was then selected by presenting the dilution series of artificial saliva pairwise in a two alternative-forced-choice procedure in which the subject indicated “which of these two solutions tastes most like nothing?” The subject was next trained to make ratings using the general labeled magnitude scale (gLMS) for intensity ratings (Green, Dalton et al. 1996, Bartoshuk, Duffy et al. 2004) and the labeled hedonic scale (LHS) for liking ratings (Lim, Wood et al. 2009).
In order to familiarize the subject with the stimuli, the ten different beverages were first presented (once each) without requiring the subject to make any ratings. The subject was instructed to take the solution entirely into her/his mouth, swish it around, and expectorate into a sink. The subject then rinsed and paused for 30 seconds before continuing to the next sample. Next, utilizing the same sip-and-spit procedure the ten different beverages were each presented three times (counterbalanced pseudo-random orders), but before rinsing the subject was instructed to rate the stimulus for overall intensity, sweetness intensity, liking and wanting. Wanting was measured with a VAS with the labels “I would never want to drink this” at the left anchor, “neutral” in the middle and “I would want to drink this more than anything” on the right anchor). The presentation order of the scales was counterbalanced across subjects. Averages were obtained for each flavor rating. The averaged liking ratings were evaluated to determine if a subset of five flavors was rated above “neutral” (0) but below “like moderately” (17.82) on the LHS. The five flavors were also required to be similarly liked, for which there needed to be overlap between standard deviations of the averaged liking ratings. If such a subset of flavors could be determined, the subject continued in the pre-conditioning session (and the subset of five eligible flavors became that subject’s “conditioning” flavors for the exposure phase). If not, the subject was excluded from further participation. Approximately 40% of subjects were excluded for this reason, but we felt that it was justified so that we could rule out baseline liking ratings as contributing to the predicted increases in liking resulting from conditioning. 
To verify that study participants could not detect the presence of maltodextrin (purportedly a tasteless and odorless carbohydrate) in the exposure phase of the experiment, they participated in a triangle test in which they indicated which of three cups was different. All cups contained the same flavor, but for each trial, either one or two cups also contained maltodextrin. Eight trials were conducted. We used the binomial distribution to set our criteria for maltodextrin detection; specifically, the minimum number of correct judgments to establish significance for the triangle test (one-tailed, a = 0.05, z = 1.64, probability of guessing p = 1/3) was calculated according to the formula
  
where n = number of trials, X = minimum number of correct judgments, and z = 1.64 if a is set to 5% (Lawless and Heymann 1999). Therefore, for n = 8 tests, the minimum number of correct judgments X=6. 
Following this the subject participated in a training session in the fMRI simulator, in order to familiarize the individual with the task and to confirm they were comfortable with all aspects of the fMRI experimental procedure (no subject reported experiencing discomfort with the procedure). For the training, the subject underwent one full 13-minute run in the fMRI simulator. Briefly, while lying supine in an fMRI simulator, we presented 1ml aliquots Sobe Lifewaters (mango melon and black and blueberry), and a photo of a PET-bottle containing the Sobe Lifewater. 

Exposure phase
Stimuli 
Based on the subject’s liking of the ten flavors, a subset of five were selected to be paired with the five caloric doses, and consumed by the subjects during the exposure sessions. Each of these flavors was paired with a specific nutrient dose by adding maltodextrin at five different increments (0, 37.5, 75, 112.5, or 150 calories), with the highest dose equivalent to a standard 12 fl oz (355 ml) can of soda. We created a total of six 355 ml beverages for each flavor-nutrient load combination, in PET-bottles. Beverage flavor, color, caloric load, and presentation order were all counterbalanced and mixed by one of the authors (MGV) who was not in contact with the subject during the exposure sessions. The beverages were not labeled for their caloric content at any time. Thus the conditioning phase of this study was double-blind.
Procedure 
There were a total of ten exposure days, divided into five sets of two consecutive days. During each set of two exposure days one of the five selected in-lab beverages (with its specific caloric load) was consumed on six different occasions following the 36 hours after the first in-lab exposures to that beverage. Subjects were encouraged to consume the same breakfast at the same time during all exposure days. During the first exposure day, the subject came to the lab for a lunch session, which was scheduled to take place 30 minutes before the subject’s normal lunch time and at least four hours after their normal breakfast time. The session began with a cheek swab, completion of a food diary on the content and time of their breakfast that morning, and rating their internal state (see above). Following their ratings, the subject consumed the beverage at their own pace. Immediately after the drink the subject made another set of internal state ratings, relaxed for 30 minutes, and then again rated their internal state. Subsequently, they were provided with a lunch (of their choice, but fixed across lunch sessions) that they consumed in the lab before rating their internal state one final time. The subject returned to the lab four hours later for their dinner session having not consumed anything (but water) between sessions. The dinner session followed the same procedure as the lunch session, except that the dinner session ended with the ratings made after the 30 minute wait, at which time the subject was instructed to eat dinner autonomously outside the lab. Previous work (Appleton, Gentry et al. 2006) has shown that FNL also occurs for stimuli consumed outside a lab setting, so in order to maximize the number of exposures subjects were given another four bottles (of the same beverage). Subjects were instructed to consume their four beverages at four different time points between that evening and the following evening: 1) one hour after dinner, 2) one hour before lunch the next day, 3) one hour before dinner the next day, and 4) one hour after dinner the next day. To encourage compliance subjects signed a sheet stating that they adhered to the instructions to the best of their ability, and returned the empty bottles to the lab. All subjects complied with these instructions. The five sets of exposure days were all completed within a two week period.

Post-conditioning session
The same stimuli and procedures from pretest were used to collect ratings for the ten beverages (without calories added) at a post-conditioning session that occurred before the fMRI scan. 

fMRI scan 
Stimuli and stimulus delivery
The subjects’ five exposure beverages (without calories added) were used during the fMRI session, and the flavorless solution was used as both the rinse and a control stimulus. The subject’s exposure flavors and selected tasteless solution were delivered as 1mL of solution over 4 s from syringe pumps with a gustometer system that has previously been described in detail (Veldhuizen, Bender et al. 2007). In brief, this system consists of computer-controlled syringe pumps which infuse liquids from syringes filled with flavor solutions into an fMRI-compatible custom designed gustatory manifold via 25-foot lengths of Tygon beverage tubing (Saint-Gobain Performance Plastics, Akron, OH, USA). The gustatory manifold is mounted on the MRI headcoil and the tubes anchor into separate channels that converge over a stylus, which rests just inside the subject’s mouth. When a pump is triggered liquid drops from the channel onto the stylus and comes in contact with the tongue. 
Experimental Design
During the fMRI scanning session, the subject performed one anatomical run and a total of three functional runs, each 13 minutes long. A long event-related design was used (for details of events within each trial see Fig. 1). During each of the runs, each flavor that was selected for the exposure sessions as well as the flavorless control was presented six times in a pseudo-random order, resulting in a total of eighteen repeats for each stimulus.  
fMRI Data Acquisition
We measure the blood oxygenation-level dependent (BOLD) signal as an indication of cerebral brain activation with echo planar imaging, acquired on a Siemens 3T TIM Trio scanner. Echo planar imaging was used to measure the blood oxygenation-level dependent (BOLD) signal as an indication of cerebral brain activation. A susceptibility-weighted single-shot echo planar method was used to image the regional distribution of the BOLD signal with parameters of: TR: 2000ms; TE: 20 ms; flip angle: 90°; FOV: 220 mm; matrix: 64 x 64; slice thickness: 3 mm, and number of slices: 40. Slices were acquired in an interleaved mode to reduce the crosstalk of the slice selection pulse. At the beginning of each functional run, the MR signal was allowed to equilibrate over six scans for a total of 12 s, which were then excluded from analysis. The anatomical scan used a T1-weighted 3D FLASH sequence (TR/TE: 2530/3.66 ms; flip angle: 20°; FOV: 256; matrix: 256 x 256; slice thickness: 1 mm; number of slices: 176).

Debriefing
Immediately after the fMRI scan the subject was debriefed about the goal of the study, the manipulation with the caloric dose of the beverages, and saliva collection. None of the subjects professed any awareness of the manipulation.