Brain Representation of Food Reward as a Function of Smoking Status
Final Report Abstract
Project # 1: Greater Perceived Ability to Form Vivid Mental Images in Individuals with High Compared to Low BMl The phenomenon of food craving has been defined as "an irresistible urge to consume a specific food". According to Kavanagh's Elaborated Intrusion Theory of Desire, mental imagery is an important factor in eliciting cravings. We reasoned that the ability to form mental images, like craving intensity, should vary according to body mass index (BMl). In this study we tested whether perceived imagery ability and the reported hedonic impact of imaging food vary with BMl. 25 healthy subjects with a range in BMl (17.7 kg/m2 - 34.2 kg/m2) were investigated: 14 subjects in the low (mean ± SE: 21.1±0.5 kg/m2), 11 in the high BMl group (mean ± SE: 28.3±0.8 kg/m2). A follow-up study with 57 subjects (BMl range: 19.1 kg/m2 - 38.7 kg/m2) was performed. Three different measures of perceived mental imagery ability (The Vividness of Visual Imagery Questionnaire, The Vividness of Olfactory Imagery Questionnaire (VOIQ), The Vividness of Food Imagery Questionnaire), and one measure of craving (Food-Craving Inventory) were assessed. Affective ratings of food aromas and flavors were evaluated. Participants with high BMl perceived themselves as better imagers than participants with low BMl. A regression analysis with scores on the imagery and craving questionnaires showed that the VOIQ accounted for the greatest amount of variance in BMl. The hedonic impact of imaging was positively correlated with the vividness of food and olfactory imagery as well as craving frequency and tended to be greater in high BMl subjects. In summary, perceived ability to form vivid mental images is related to craving frequency and hedonic impact of imaging and is a significant predictor of BMl. These are fundamental new findings that contribute important information to the understanding of the development of food cravings. Project #2: Greater Response in the Insula and Midbrain to Unexpected versus Expected Sweet Taste The results of earlier studies suggest that neural responses to taste in the primary taste cortex are modulated by expectations and not solely by the objective qualities of taste. Nitschke and colleagues showed that mislabeling an aversive bitter taste as mildly aversive results in a decrease in rated perceived unpleasantness and a decrease in insular fMRl response. We used fMRl to test whether whole brain response to a sweet taste varies as a function of whether it is expected or unexpected. A 2x2 factorial design was employed with expectation (valid or invalid cues consisting of the spoken word "sweet" or "tasteless") and stimulus (tasteless or 0.56M sucrose solution) as within-subject factors. This gave rise to a measure of brain response during four different conditions: 1) hearing "sweet" followed by receipt of sucrose (expected sweet); 2) hearing "sweet" followed by receipt of tasteless (unexpected tasteless); 3) hearing "tasteless" followed by receipt of sucrose (unexpected sweet); and 4) hearing "tasteless" followed by receipt of tasteless (expected tasteless). 70% ofthe trials were valid (conditions 1 and 4). As predicted, we found a main effect of expectation such that sensory, attentional and reward regions responded significantly more to tasteless and to sweet solutions when unexpected. We also observed a stimulus by expectation interaction with greater response in the midbrain and the bilateral anterior insula during receipt of sweet when it was not expected. These findings are consistent with prior work showing that midbrain dopamine neurons and their target regions respond preferentially to unexpected food reward. Our results extend prior knowledge by showing that the encoding of sweet taste in primary sensory cortex is influenced by expectation. These findings highlight the impact of reward context effects on early encoding of gustatory stimuli in the human brain. Project #3: Brain Representation of Food Reward as a Function of Smoking Status The goal of this project was to use functional magnetic resonance imaging (fMRl) to test the hypothesis that brain representation of food reward changes as a function of smoking status. The specific aims of the study were: 1) To test the prediction that smoking status (smoker, non-smoker, acutely deprived smoker) influences perceptual and behavioural responses to food reward. 2) To use fMRl to test the prediction that an appetitive food odour induces greater activity in regions encoding incentive salience in acutely abstinent smokers compared to non-smokers and non-smokers compared to smokers. Due to severe difficulties with subject recruitment up to date only 7 smokers and 2 abstinent smokers finished all four longitudinal steps of the study including one fFMRI scan. As for nonsmoking participants we collected complete data from 33 subjects. Data collection and analyzes are still ongoing.
Publications
- Human Brain Response to an Unexpected Sweet Taste Stimulus. John B. Pierce Laboratory Seminar Series. New Haven, CT, USA, 2007
Aschenbrenner K
- Dieting and disordered eating in German high school athletes and non-athletes. Scandinavian Journal of Medicine & Science in Sports (epub ahead of print, June 17,2008)
Rosendahl J, Bormann B, Aschenbrenner K, Aschenbrenner F, Strauss B
- Einfluss eines Riechverlustes auf die Ernährung (The influence of smell loss on dietary patterns. 79. Jahresversammlung der Deutschen Gesellschaft fiir Hals-Nasen-Ohren-Heilkunde, Kopf- und Hals-Chirurgie e. V., Bonn, Germany, 2008
Hummel T, Seo HS, Teszmer K, Krone F, Hummel C, Ishimaru T, Aschenbrenner K
- Gustatory and Olfactory Sensitivity in Patients with Anorexia and Bulimia in the Course of Treatment. Journal of Psychiatric Research 2008; 43(2): 129-37
Aschenbrenner K, Scholze N, Joraschky P, Hummel T
- Olfaktorische und gustatorische Sensitivität bei Patientinnen mit Anorexie und Bulimie. Medizinische Doktorarbeit an der Technischen Universität. Dresden, 2008
Scholze N
- Preferential response to food compared to nonfood odors in the insula and operculum. International Symposium on Olfaction and Taste/ AChemS Meeting. San Francisco, USA, 2008
Bender G, Negoias S, Hummel T, Gerber, J, Aschenbrenner K, Gitelman DR, Small DM
- Sweet expectations: Greater response in the anterior insula and midbrain to unexpected compared to expected sweet taste. International Symposium on Olfaction and Taste/ AChemS Meeting. San Francisco, USA, 2008
Small DM, Aschenbrenner K, Veldhuizen M, Felsted J
- The Influence of Olfactory Loss on Dietary Behaviors. Laryngoscope 2008; 118(1): 135-144
Aschenbrenner K, Hummel C, Teszmer K, Krone F, Ishimaru, T, Seo HS, Hummel, T
