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“Is Butter a Carb?” Neural mechanisms of nutrient-sensing and food reward in the human brain



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Khorisantono, Putu 


Sensing the nutrient composition of a food and the processing of this information by the brain’s reward system to regulate food consumption are crucial biological needs. However, dysfunction in neural reward pathways may also lead to overconsumption of certain nutrients, contributing to obesity and comorbid diseases. In the context of fat, the oral sensory mechanism of its detection is disputed, although there is substantial evidence for fat detection through oral textural properties. In this thesis, I investigate the neural correlates related to the specific textural properties of oral food stimuli with defined nutrient contents, as well as their formally measured economic reward values and psychophysical ratings during functional Magnetic Resonance Imaging (fMRI) in healthy human volunteers. These results are then correlated with an ad-libitum naturalistic eating test. The thesis contains the following chapters: Chapter I discusses the key background literature; Chapter II focuses on the optimisation of the design and stimuli; Chapter III provides a detailed analysis of behavioural data, through basic psychophysical ratings of food stimuli and modelling of subjective value data; Chapter IV describes the results of the neuroimaging component of the experiment, and Chapter V discusses the results of the project in the context of current literature. This project investigates the textural contributions to sensory fat detection and reward valuation. Crucially, it is the first time a formal fMRI investigation is done on the oral-lubricative nature of fat, demonstrating encoding of sliding friction in the midposterior insula and the oral somatosensory cortex, which supports the concept that fat detection occurs through texture. Furthermore, our results highlight the unique role of the orbitofrontal cortex in processing food texture parameters, their subjective perception, and integration to subjective value, before subsequent evaluation in the ventromedial prefrontal cortex.





Grabenhorst, Fabian


nutrition, neuroscience, fMRI, reward, orbitofrontal cortex, ventromedial prefrontal cortex, coefficient of sliding friction, macronutrient, oral fat


Doctor of Philosophy (PhD)

Awarding Institution

University of Cambridge
Wellcome Trust Henry Dale Fellowship (Fabian Grabenhorst)