Dietary fiber and WHO food categories extension for the food-pics_extended database

Well characterized databases used for experimental purposes with extensive meta-data are essential for conducting meaningful and comparable studies. The Food-pics_extended database (Blechert et al., 2019) is one example for a widely used food stimulus database (original publication Blechert et al., 2014: 285 citations, and 2019: 32 citations). Indeed, meta-data on low level and high level image characteristics is broad, yet fiber ratings are not included, limiting its use in diet-related studies. Therefore, we developed fiber ratings per item (n = 562 stimuli), based on mean values of four non-expert raters. Ratings show good reliability (ICC = 0.77) and meaningful ranges per food type (mean fiber per 100 g by food type minbeverages = 0.04 ± 0.04 g and max Ready-to-eat savories = 4.49 ± 1.58). The newly provided fiber ratings enrich the already valuable database and extend it by an important nutrient value for human and planetary health

art.pics Database: An open access database for art stimuli for experimental research

While art is omnipresent in human history, the neural mechanisms of how we perceive, value and differentiate art has only begun to be explored. Functional magnetic resonance imaging (fMRI) studies suggested that art acts as secondary reward, involving brain activity in the ventral striatum and prefrontal cortices similar to primary rewards such as food. However, potential similarities or unique characteristics of art-related neuroscience (or neuroesthetics) remain elusive, also because of a lack of adequate experimental tools: the available collections of art stimuli often lack standard image definitions and normative ratings. Therefore, we here provide a large set of well-characterized, novel art images for use as visual stimuli in psychological and neuroimaging research. The stimuli were created using a deep learning algorithm that applied different styles of popular paintings (based on artists such as Klimt or Hundertwasser) on ordinary animal, plant and object images which were drawn from established visual stimuli databases. The novel stimuli represent mundane items with artistic properties with proposed reduced dimensionality and complexity compared to paintings. In total, 2,332 novel stimuli are available open access as “art.pics” database at https://osf.io/BTWNQ/ with standard image characteristics that are comparable to other common visual stimuli material in terms of size, variable color distribution, complexity, intensity and valence, measured by image software analysis and by ratings derived from a human experimental validation study [n = 1,296 (684f), age 30.2 ± 8.8 y.o.]. The experimental validation study further showed that the art.pics elicit a broad and significantly different variation in subjective value ratings (i.e., liking and wanting) as well as in recognizability, arousal and valence across different art styles and categories. Researchers are encouraged to study the perception, processing and valuation of art images based on the art.pics database which also enables real reward remuneration of the rated stimuli (as art prints) and a direct comparison to other rewards from e.g., food or money

Do wanting, hunger and brain microstructure predict recognition performance and lure discrimination of food items? A pre-registered analysis

Individual food wanting predicted food memory in this sample of young, overweight adults. This might help to improve weight-loss interventions. To better understand reward-related determinants of food memory, we currently investigate reward-related brain activity during encoding and recognition

How do memory and attention influence food decisions and what are the underlying neuronal mechanisms?

Escalating world-wide obesity prevalence urges the need to understand unhealthy eating behaviour and potential modifiers. Human behavioural studies suggest that besides the internal state (hungry or satiated) and external interaction (attention to food cues) also learning and memory play an important role in food preferences and decisions (Booth et al., 1982; Laney et al., 2007). Namely, being hungry increases arousal and the susceptibility for food cues (Montagrin et al., 2019). This increased attention to food cues might explain that hunger leads to better memory performance for food versus non-food items (Morris & Dolan, 2001). However, little is known about the underlying neurobiological mechanisms, whether food memory is influenced by the individual's preferences or if the process is biased by attention deficits. We thus aim to determine the interplay of memory, attention and food desires and related underlying mechanisms in the context of food cue evaluation. Therefore, we are conducting a neuroimaging study on food wanting, memory and attention with overweight participants (n=60, BMI: 25-30kg/m²) featuring rather naive eating behaviour. Measures of interest are hippocampus and amygdala activity during memory encoding and retrieval in two subsequent fMRI tasks (Thieleking et al., in prep), (food) wanting ratings, performance during retrieval, hunger ratings, brain microstructure (from diffusion-weighted imaging) and attention efficiency assessed by the Attention Network Test (Fan et al., 2002). Lastly, we study longitudinal changes in memory performance and attention efficiency after a two-week dietary intervention. Findings of this dietary intervention could pave the way for new approaches to reduce unhealthy eating behaviour and eventually overweight and obesity

The Effect of Polyphenols on Working and Episodic Memory in Non-pathological and Pathological Aging: A Systematic Review and Meta-Analysis

Life expectancy steadily increases, and so do age-associated diseases, leading to a growing population suffering from cognitive decline and dementia. Impairments in working memory (WM) and episodic memory (EM) are associated with an increased risk of developing dementia. While there are no effective pharmacological therapies to preserve or enhance cognition and to slow down the progression from mild memory complaints to dementia so far, plant-based nutrients including polyphenols have been suggested to exert beneficial effects on brain aging. This review studies whether supplementary polyphenols are effective in preserving or enhancing memory in both non-pathological and pathological aging, and whether there are polyphenol efficiency differences between WM and EM. A systematic literature search was conducted and 66 out of 294 randomized clinical trials with 20 participants or more per group, aged 40 years or older were included. These covered a daily intake of 35–1,600 mg polyphenols, e.g., flavonols, flavonoids, isoflovones, anthocyanins, and/or stilbenes, over the course of 2 weeks to 6.5 years duration. In total, around half of the studies reported a significantly improved performance after polyphenol administration compared to control, while three studies reported a worsening of performance, and the remainder did not observe any effects. According to pooled WM and EM meta-analysis of all memory outcomes reported in 49 studies, overall effect size for WM and EM indicated a significant small positive effect on EM and WM with similar estimates (b ~ 0.24, p < 0.001), with large study heterogeneity and significant Funnel asymmetry tests suggesting a positivity bias. These results remained similar when excluding studies reporting extremely large positive effect sizes from the meta-analyses. While Ginkgo biloba and isoflavones did not show benefits in subgroup meta-analyses, those suggested some effects in extracts containing anthocyanins, other flavonoids and resveratrol, again potentially resulting from publication bias. To conclude, a systematic review and meta-analysis indicate that short- to moderate-term polyphenol interventions might improve WM and EM in middle-to older aged adults, however, publication bias in favor of positive results seems likely, rendering definite conclusions difficult. Future studies with larger, more diverse samples and sensitive monitoring of cardiovascular, metabolic and beginning brain pathologies as well as longer follow-up are needed to better understand the impact of age, (beginning) pathologies, gender, and long-term use on polyphenol action.Peer Reviewe

Dietary and serum tyrosine, white matter microstructure and inter-individual variability in executive functions in overweight adults: Relation to sex/gender and age

Tyrosine (tyr), the precursor of the neurotransmitter dopamine, is known to modulate cognitive functions including executive attention. Tyr supplementation is suggested to influence dopamine-modulated cognitive performance. However, results are inconclusive regarding the presence or strength and also the direction of the association between tyr and cognitive function. This pre-registered cross-sectional analysis investigates whether diet-associated serum tyr relates to executive attention performance, and whether this relationship is moderated by differences in white matter microstructure. 59 healthy, overweight, young to middle-aged adults (20 female, 28.3 ± 6.6 years, BMI: 27.3 ± 1.5 kg/m2) drawn from a longitudinal study reported dietary habits, donated blood and completed diffusion-weighted brain magnetic resonance imaging and the attention network test. Main analyses were performed using linear regressions and non-parametric voxel-wise inference testing. Confirmatory analyses did neither support an association between dietary and serum tyr nor a relationship between relative serum tyr/large neutral amino acids (LNAA) levels or white matter microstructure and executive attention performance. However, exploratory analyses revealed higher tyr intake, higher serum tyr and better executive attention performance in the male sex/gender group. In addition, older age was associated with higher dietary tyr intake and lower fractional anisotropy in a widespread cluster across the brain. Finally, a positive association between relative serum tyr/LNAA and executive attention performance was found in the male sex/gender group when accounting for age effects. Our analysis advances the field of dopamine-modulated cognitive functions by revealing sex/gender and age differences which might be diet-related. Longitudinal or intervention studies and larger sample sizes are needed to provide more reliable evidence for links between tyr and executive attention

The GUT-BRAIN study: Short-term effect of a high-fiber diet on gut-brain communication

Background. Based on recent experimental neuroscientific studies, it has been suggested that high-fiber diets, rich in naturally occurring prebiotics such as soluble fibers, might affect brain structure and functions through changes in the gut microbiome. However, due to a lack of evidence from randomized controlled trials in humans, it remains to be shown whether fibers affect brain structure and cognitive function through “bottom-up” metabolic mechanisms via the gut-brain axis. Aim. We therefore aim to elucidate whether there is a causal link between diet, gut microbial signalling and the brain. To do so, we are conducting a double-blind within-subject cross-over dietary intervention study with inulin as high-fiber supplement versus placebo. This study includes the analysis of blood-based biomarkers and stool-derived microbiota composition, as well as the assessment of task-based brain activation in food decision making and memory performance. Hypotheses. We hypothesize that supplementary high-fiber compared to placebo intake modulates food wanting and memory performance and its neuronal correlates. We further presume that changes in the gut microbial composition (e.g. higher α- and β-diversity) and in carbohydrate-specific metabolic pathways (e.g. short-chain fatty acid synthesis) may mediate potential effects of the high-fiber diet. Methods. Each participant (ntotal = 60, 18-45 years old) takes part in five experiment days out of which four include MRI sessions (Siemens Magnetom Prisma 3T) directly before and after the dietary intervention/placebo period. As dietary intervention, participants take 30g of inulin supplement (extracted from the chicory plant) daily for two weeks or a calorie-matched placebo supplement (maltodextrin) while maintaining their usual omnivorous diet. Food wanting and memory performance and related brain activity are assessed using functional magnetic resonance imaging (fMRI, 3T, TR 2000ms, 2mm³ isotropic). Briefly, participants have to indicate wanting of different food and, as contrast condition, art stimuli on an 8-point Likert scale. Memory performance is assessed after a delay of 20 minutes (fMRI) and after 12 weeks (behaviour). We further collect structural and diffusion-weighted images. Besides brain imaging, participants perform the Attentional Network Test. In addition, we monitor anthropometry, metabolic and emotional health makers with blood samples and questionnaires (e.g. WHO 5, BDI-II, GQLI, PANAS) as well as fecal samples to characterize microbial diversity (16S rRNA gene sequencing) and metabolic activity. Conclusions. This randomized controlled trial comprehensively determines the effects of a high-fiber dietary intervention on food wanting and neuronal correlates and whether these effects are mediated by changes in gut microbial composition and metabolism. Advantages of the study design are the within-subject contrasts which account for the large inter-individual differences in gut microbial composition and in the evaluation of food items. Further, we thoroughly control for hunger state, personal characteristics and other confounders. Art pictures as non-food control stimuli showed consistent activation of brain-areas related to wanting evaluation. Therefore, we propose our fMRI task as a robust and reliable tool to evaluate specific aspects of food wanting against other reward dimensions. This study will help to elucidate whether high-fiber diets affect body and brain and which underlying mechanisms mediate these effects

Estimating the effect of a scanner upgrade on measures of grey matter structure for longitudinal designs

Longitudinal imaging studies are crucial for advancing the understanding of brain development over the lifespan. Thus, more and more studies acquire imaging data at multiple time points or with long follow-up intervals. In these studies changes to magnetic resonance imaging (MRI) scanners often become inevitable which may decrease the reliability of the MRI assessments and introduce biases. We therefore investigated the difference between MRI scanners with subsequent versions (3 Tesla Siemens Verio vs. Skyra) on the cortical and subcortical measures of grey matter in 116 healthy, young adults using the well-established longitudinal FreeSurfer stream for T1-weighted brain images. We found excellent between-scanner reliability for cortical and subcortical measures of grey matter structure (intra-class correlation coefficient > 0.8). Yet, paired t-tests revealed statistically significant differences in at least 67% of the regions, with percent differences around 2 to 4%, depending on the outcome measure. Offline correction for gradient distortions only slightly reduced these biases. Further, T1-imaging based quality measures reflecting gray-white matter contrast systematically differed between scanners. We conclude that scanner upgrades during a longitudinal study introduce bias in measures of cortical and subcortical grey matter structure. Therefore, before upgrading a MRI scanner during an ongoing study, researchers should prepare to implement an appropriate correction method for these effects

The new biology of ageing

Human life expectancy in developed countries has increased steadily for over 150 years, through improvements in public health and lifestyle. More people are hence living long enough to suffer age-related loss of function and disease, and there is a need to improve the health of older people. Ageing is a complex process of damage accumulation, and has been viewed as experimentally and medically intractable. This view has been reinforced by the realization that ageing is a disadvantageous trait that evolves as a side effect of mutation accumulation or a benefit to the young, because of the decline in the force of natural selection at later ages. However, important recent discoveries are that mutations in single genes can extend lifespan of laboratory model organisms and that the mechanisms involved are conserved across large evolutionary distances, including to mammals. These mutations keep the animals functional and pathology-free to later ages, and they can protect against specific ageing-related diseases, including neurodegenerative disease and cancer. Preliminary indications suggest that these new findings from the laboratory may well also apply to humans. Translating these discoveries into medical treatments poses new challenges, including changing clinical thinking towards broad-spectrum, preventative medicine and finding novel routes to drug development