A complete scientific understanding of human nature requires delineation of the neurobiological characteristics underlying the unique features of the human mind. This effort can be facilitated by comparing the human brain with the brains of other living primate species. Humans are more susceptible to neurodegenerative diseases than other primate species, including our closest living primate relatives, the chimpanzees. Comparing age-related changes in brain structure between humans and non-human primates could, therefore, potentially shed light on the neurological basis of this human vulnerability. Further, human brains are lateralized with specialized cognitive and behavioral functions. Comparing the magnitude of hemispheric asymmetries in brain structure between humans and non-human primates can probe insights into this human specific capability and learn more about human evolution. Diffusion weighted MRI protocols were developed for different species, taking into account their neuroanatomical differences. For Chimpanzees, a multi-shot DWI sequence was developed and compared with a single-shot DWI sequence to determine which provided a better quality diffusion data free of acquisition related artifacts. Different simulation techniques were used to evaluate the effect of segmentation-related motion artifact (ghosting) on the multi-shot DTI data. Although both protocols generated high-resolution diffusion MRI data with correctable susceptibility-induced distortions, the single-shot protocol enables the acquisition of the high-resolution diffusion MRI data freed of ghosting and with twice the signal-to-noise ratio (SNR), for the same scan duration. The acquired chimpanzee and macaque diffusion data were used to compare the magnitude of microstructural asymmetries and age-related decline of brain white matter with those in humans. Hemispheric asymmetry results show a pattern of strong leftward asymmetry in human DTI indices that differs markedly from the chimpanzee (multi-shot data) and the rhesus macaque patterns involving both rightward and leftward asymmetries. The magnitude of leftward asymmetry increased for chimpanzees scanned with single-shot DTI sequence. Region of interest analyses within the corpus callosum revealed a significant age-related increase in fractional anisotropy (FA) in the genu for chimpanzees (multi-shot data) and no significant change in any region for macaques. Additionally, voxel-wise analysis using Tract Based Spatial Statistics (TBSS) revealed widespread age-related FA increases for chimpanzees (multi-shot data) and weak age-related decreases in FA for macaques across most white matter tracts. Overall, results from these multi-shot data analyses suggest that rhesus monkeys show age-related decreases in white matter integrity that parallel changes found in humans, whereas chimpanzees show age-related increases in white matter integrity. On the contrary, the single-shot data results for chimpanzees revealed no significant relationship between age and the different DTI indices. These noteworthy species differences may help to explain the unique features of the human mind and why humans are more susceptible to neurodegenerative diseases. Furthermore, these studies demonstrate the need for complementary histological studies of white matter microstructure in humans, chimpanzees and macaques to clarify the cellular and molecular basis of these findings.

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Motivated by the rising prevalence of obesity worldwide and the global need for greater sustainability, I dedicated this dissertation to exploring new perspectives on food decision-making and to advancing neuroimaging and food-related research methods. Despite the awareness that unfavourable food choices can have serious long-term consequences on individual health and on the environment, people often struggle to break out of their dietary habits. Vicious cycles seem to inhibit individuals from shifting to healthier, more sustainable diets. Successful therapies and policies are required to prevent the pandemic development of obesity. Hence, there is an acute need to understand the complex mosaic of food choices, including cognitive, physiological and neuroanatomical factors. Using a randomized controlled trial (RCT) and diffusion-weighted magnetic resonance imaging (DWI), I was able to uncover a so far undetected potentially vicious cycle of reward-enhanced and calorie-biased food recognition memory. Consequently, the reward- and calorie-bias combined with the over-representation of high-caloric food in our environment might be inhibiting healthier food choices. On the neural level, I assessed the microstructural coherence of the uncinate fasciculus (UF) which connects reward with memory brain areas. The UF's coherence did not influence the enhancement of memory by 'desire-to-eat' in our healthy, overweight study participants. Weight-loss interventions could profit from reward-enhanced memorability by promoting the desire to eat healthier food options. In obese individuals, though, white matter coherence is often decreased and could counteract the success of such interventions. To facilitate and encourage further research on eating behaviour and interventions, I co-developed methodological advancements such as food-related tasks for MRI use, an open-access stimulus database, a tool to evaluate nutrient intake, and the extension of a food picture database by important characteristics. As DWI revealed to be noise- and artefact-sensitive, I also aimed to optimize DWI processing pipelines, namely artefact reduction and white matter skeleton reconstruction. Replicability and sustainability efforts in this dissertation are reflected in the choice of statistical tools and application of Open Science practices.:1 Introduction 1.1 The scope of food decisions 1.1.1 Individuals and their well-being and health 1.1.2 Societal well-being and functioning 1.1.3 Environment and climate change 1.2 The cognition of food decisions 1.2.1 Neural mechanisms of food choices 1.2.2 Food decision-making in obesity 1.3 The research on food decision-making—Methods and Tools 1.3.1 Assessing dietary habits and food intake 1.3.2 Functional neuroimaging 1.3.3 Experimental stimuli 1.3.4 Diffusion-weighted imaging of brain microstructure 1.3.5 Statistical Analysis 1.4 Interim Summary 2 Publications 2.1 art.pics Database: An Open Access Database for Art Stimuli for Experimental Research. 2.2 Same Brain, Different Look?—The Impact of Scanner, Sequence and Preprocessing on Diffusion Imaging Outcome Parameters. 2.3 Nutrient scoring for the DEGS1-FFQ—from food intake to nutrient intake. 2.4 Neurocognitive predictors of food memory in healthy adults—a preregistered analysis. 3 Conclusions Summary Neurocognitive determinants of food memory Implications for the obesity pandemic DWI in Neuroimaging Stimuli in Neuroimaging Food and nutrient intake assessment Open Science and Sustainability References Darstellung des eigenen Beitrags Erklärung über die eigenständige Abfassung der Arbeit Curriculum vitae Verzeichnis der wissenschaftlichen Veröffentlichungen und Vorträge Danksagung / Motiviert durch die steigende Prävalenz von Adipositas weltweit und den globalen Bedarf an mehr Nachhaltigkeit widmete ich diese Dissertation der Erforschung neuer Perspektiven auf Essentscheidungen und der Weiterentwicklung von Methoden zur Hirnbildgebung und Erforschung von Ernährung. Obwohl bekannt ist, dass ungünstige Nahrungswahl langfristig gravierende Folgen für die individuelle Gesundheit und die Umwelt haben kann, fällt es Menschen oft schwer, ihre Ernährungsgewohnheiten zu ändern. Teufelskreise scheinen Individuen daran zu hindern, zu gesünderen, nachhaltigeren Ernährungsweisen zu wechseln. Erfolgreiche Therapien und politische Maßnahmen sind erforderlich, um den globalen Anstieg von Adipositas zu verhindern. Daher besteht ein akuter Bedarf, das komplexe Mosaik der Essentscheidungen zu verstehen, einschließlich kognitiver, physiologischer und neuroanatomischer Faktoren. Durch eine randomisierte kontrollierte Studie und diffusionsgewichtete Magnetresonanztomographie (dwMRT) konnte ich einen bislang unentdeckten potenziellen Kreislauf des belohnungsverstärkten und kalorienverzerrten Lebensmittelgedächtnis aufdecken. Diese Kombination aus Belohnungs- und Kalorienbias, zusammen mit der Überrepräsentation hochkalorischer Lebensmittel in unserer Umgebung, könnte gesündere Essentscheidungen behindern. Auf neuronaler Ebene evaluierte ich die mikrostrukturelle Kohärenz des Fasciculus uncinatus (FU), der Belohnungs- mit Gedächtnisarealen des Gehirns verbindet. Die Kohärenz des FU hatte keinen Einfluss auf die Verstärkung des Gedächtnisses durch das „Verlangen zu essen“ bei unseren übergewichtigen Studienteilnehmenden, da deren Nervenfasern noch gesund waren. Gewichtsreduktionstherapien könnten daher von der belohnungsverbesserten Einprägsamkeit profitieren, indem sie das Verlangen nach gesünderen Nahrungsmitteln fördern. Bei Personen mit Adipositas ist die Kohärenz der weißen Substanz jedoch oftmals verringert, was den Erfolg solcher Interventionen schon beeinträchtigen könnte. Um weitere Forschung zu Essverhalten und Interventionen zu erleichtern und zu fördern, entwickelte ich Methoden wie Aufgaben zu Essentscheidungen und Essensgedächtnis für die Verwendung im MRT, eine öffentlich zugängliche Stimulusdatenbank, ein Tool zur Auswertung der Nährstoffaufnahme und die Erweiterung einer Lebensmitteldatenbank um wichtige Merkmale. Da sich dwMRT als anfällig für Rauschen und Artefakte erwies, hatte ich auch das Ziel, die dwMRT-Verarbeitungs-Pipelines zu optimieren, insbesondere die Artefaktreduzierung und die Rekonstruktion der Nervenbahnen der weißen Substanz. Die Reproduzierbarkeits- und Nachhaltigkeitsbemühungen dieser Dissertation spiegeln sich in der Wahl der statistischen Methoden und der Anwendung von Open-Science-Praktiken wider.:1 Introduction 1.1 The scope of food decisions 1.1.1 Individuals and their well-being and health 1.1.2 Societal well-being and functioning 1.1.3 Environment and climate change 1.2 The cognition of food decisions 1.2.1 Neural mechanisms of food choices 1.2.2 Food decision-making in obesity 1.3 The research on food decision-making—Methods and Tools 1.3.1 Assessing dietary habits and food intake 1.3.2 Functional neuroimaging 1.3.3 Experimental stimuli 1.3.4 Diffusion-weighted imaging of brain microstructure 1.3.5 Statistical Analysis 1.4 Interim Summary 2 Publications 2.1 art.pics Database: An Open Access Database for Art Stimuli for Experimental Research. 2.2 Same Brain, Different Look?—The Impact of Scanner, Sequence and Preprocessing on Diffusion Imaging Outcome Parameters. 2.3 Nutrient scoring for the DEGS1-FFQ—from food intake to nutrient intake. 2.4 Neurocognitive predictors of food memory in healthy adults—a preregistered analysis. 3 Conclusions Summary Neurocognitive determinants of food memory Implications for the obesity pandemic DWI in Neuroimaging Stimuli in Neuroimaging Food and nutrient intake assessment Open Science and Sustainability References Darstellung des eigenen Beitrags Erklärung über die eigenständige Abfassung der Arbeit Curriculum vitae Verzeichnis der wissenschaftlichen Veröffentlichungen und Vorträge Danksagung

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