AFFECT MODULATES APPETITE-RELATED BRAIN ACTIVITY TO IMAGES OF FOOD KILLGORE, W. & YURGELUN-TODD, D. (2006) VIVIEN CHIU Are you a Carbohydrate Craver?

Introduction Thorough studies done in labs on animals, but what about us? Higher order regions of cerebral cortex involved in humans What is Affect?  Conscious subjective feeling/emotion, interaction with stimuli OBJECTIVE: To determine if cerebral activity would covary with affect ratings and if covariance pattern would differ as a function of food’s nutritional content

Brain Regions Insular cortex  Ongoing status of internal state  Responds directly to specific taste stimuli changes (salty/sweet)  Increased activation during hunger/smell of food Orbitofrontal cortices  Gathers info to converge them and evaluate overall reward potential  Medial/caudal: Heightened activity with motivation to eat  Lateral: inhibitory function related to satiety

Methods Participants  13 healthy (mean BMI = 22.1 kg/m 2 ) women, ranging from years old Imaging Methods  Over 20 contiguous coronal slices were used to collect images from blood oxygen level dependent (BOLD) fMRI  Each scan lasted 150s, with 50 images collected each time

Methods Stimulation  Three separate scanning runs:  lasted 150s each  5 alternating 30s periods with control and stimulus  10 pictures per period Low-fat/calorie-lean foods High-fat/calorie-dense foods Non-edible food related objects

Methods PANAS (Positive and Negative Effect Schedule)  PA  Pleasant enthusiasm  Active positive engagement  NA  Subjective distress  Unpleasant emotional activation

Results

Results Summary High Calorie Foods  PA with greater BOLD activity in right lateral orbitofrontal cortex  Higher NA ratings were associated with greater BOLD activity within medial regions of orbitofrontal cortex/ posterior insula Low Calorie Foods  Greater PA seen in with increase of BOLD activity from orbitofrontal cortex  Higher NA associated with increased BOLD activity in right lateral and anterior insula (might be difference between anterior and posterior)

Discussion Responsiveness/feeding related regions of brain were significantly related to PANAS ratings  Medial orbitofrontal  rewarding stimuli  Lateral orbitofrontal  punishing stimuli/inhibition of stimuli response Proposed mechanism  Relation between mood and appetite involve changes in activity of orbitofrontal cortices  Negative mood/stress  increased cravings  “Self-medicate”  high carbs = increasing serotonin

Conclusions Opinion on paper  Strengths:  Implications for people with seasonal affective disorder or bipolar depression  Underlying message about food choice  Limitations:  fMRI in-plane distortion  Small sample of only females in a limited age range working at the same hospital in Massachusetts  Correlation does not mean causation  Next steps?  Specifically correlating individual food cravings

Summary Affective state influences brain activity in response to food of varying calorie density/fat content  Negative mood  Unhealthy food choice association  shun low-calorie, low-fat  Positive mood  Fewer cravings for foods high in calorie/fat content Neurobiological mechanism may be involved between mood and food choice  Right lateral medial cortex: Reduced motivation to eat  Medial orbitofrontal/insular cortices: Increased desire to eat

Questions? Don’t be an emotional eater, be AWESOME instead