The Mediterranean diet (MedDiet) has been associated with cognitive performance. Yet, controlled trials have yielded contradictory results. To tackle this controversy, a comprehensive multimodal analysis of the association of the MedDiet with cognitive performance and brain structure in normative aging is still necessary. Here, community dwellers ≥50 years from a cohort study on normative aging (n = 76) underwent a (i) magnetic resonance imaging session with two acquisitions: structural and diffusion-weighted imaging (DWI); (ii) neuropsychological battery of tests focusing on memory and executive functioning; and (iii) dietary assessment through the Mediterranean Diet Assessment Screener (MEDAS, score range: 0–14, scores ≥10 indicate high adherence to the Mediterranean diet) 18 months prior to the brain imaging and neuropsychological assessment. We found that high adherence to the MedDiet (MEDAS ≥10) was associated with higher values of fractional anisotropy and lower diffusivity values in the brain white matter. Similarly, high adherence to the MedDiet was associated with higher structural connectivity between left hemisphere brain regions. Specifically, the amygdala, lingual, olfactory, middle occipital gyrus, and calcarine areas. No association was found between high adherence to the MedDiet and total brain volumes or hypointensities. Higher adherence to the MedDiet was positively associated with executive functioning scores. These results suggest that high adherence to the MedDiet positively associates with brain health, specifically with executive function scores and white matter integrity of bundles related to the processing and integration of taste, reward, and decision making. These findings seem to support the view that the MedDiet should be part of recommendations to promote a healthy brain.

Despite the reported benefits of diet on cognition in older adults, randomized controlled trials (RCT) testing the impact of dietary interventions on cognitive scores have yielded less promising results when cognition was assessed via neuropsychological tests. More recently, neuroimaging has been used to identify more subtle brain-related changes associated to cognition. Hence, employing a combination of neuroimaging techniques with neuropsychological tests could clarify this controversy. To determine the effect of diet on cognitive performance, we conducted a systematic review of PubMed and Scopus databases for all studies, on middle-aged and older adults, combining neuroimaging, neuropsychological tests, and data on dietary patterns. The inclusion criteria were met by 14 observational studies and no RCTs. The range of brain measures assessed varied from volumes to white matter integrity, functional connectivity, brain glucose metabolism and beta-amyloid deposition. Given the variability of methods used in assessing cognitive performance, diet and brain correlates, conducting a meta-analysis was not possible. Here the evidence suggests that, in observational studies, dietary patterns may be associated with brain correlates that have been shown to precede cognitive decline. As such, neuroimaging should be included in future RCTs to identify any benefits of diet on brain measures linked with cognitive health.

Suggestions about hunger can generate placebo effects on hunger experiences. But, the underlying neurocognitive mechanisms are unknown. Here, we show in 255 women that hunger expectancies, induced by suggestion-based placebo interventions, determine hunger sensations and economic food choices. Functional magnetic resonance imaging in a subgroup (n = 57/255) provides evidence that the strength of expecting the placebo to decrease hunger moderates medial prefrontal cortex activation at the time of food choice and attenuates ventromedial prefrontal cortex (vmPFC) responses to food value. Dorsolateral prefrontal cortex activation linked to interference resolution formally mediates the suggestion-based placebo effects on hunger. A drift-diffusion model characterizes this effect by showing that the hunger suggestions bias participants’ food choices and how much they weigh tastiness against the healthiness of food, which further moderates vmPFC–dlPFC psychophysiological interactions when participants expect decreased hunger. Thus, suggestion-induced beliefs about hunger shape hunger addressing economic choices through cognitive regulation of value computation within the prefrontal cortex.

Background Resolving the ambivalence between immediate cravings and long-term consequences is a key target of communication-based interventions toward behavioral change, such as motivational interviewing. Here, we aimed at understanding how this ambivalence between changing and sustaining unhealthy eating habits influences food valuation and its neural mechanism. Methods Eighty-five participants with varying body mass indices and food addiction-like symptoms underwent a motivational interviewing session during which they formulated personal reasons for (i.e., change talk) and against (i.e., sustain talk) changing their current eating habits. One week later, they listened to their statements when rating how much they wanted to eat various food items for real at the end of the experiment while their brain activation was measured with functional magnetic resonance imaging. Results Food choices were healthier when participants had listened to their change talk statements, and more based on taste following sustain talk statements. This effect was stronger in participants with a BMI ≥ 25 kg/m², particularly among those with more food addiction-like symptoms displayed in their everyday life eating habits. On the neural level, participants with a BMI ≥ 25 kg/m² also showed stronger functional connectivity between the ventromedial and dorsolateral prefrontal cortex at the time of food choice following a change compared to a sustain talk statement. On the contrary, participants with a BMI < 30 kg/m² displayed stronger neural craving responses when making their food choices following sustain talk. Moreover, after change talk, among participants with a BMI < 30 kg/m², those with higher BMI displayed stronger neural craving responses during healthy food wanting, and lower responses during tasty food wanting. Conclusion These findings indicate that shifting between changing and sustaining unhealthy eating habits biases food valuation and its encoding in neural pathways linked to valuation, cognitive control, and craving as a function of weight status. Study-pre-registration This study was pre-registered (https:/clinicaltrials.gov/study/NCT05101863).

Dietary self-control is associated with inter-individual differences in neuroanatomy. Yet, whether such inter-individual differences are also associated with healthier dietary patterns is yet to be determined. In this cross-sectional study, a total of 100 northern Portuguese older community-dwellers were assessed with regards to i) the adherence to a healthy dietary eating pattern - the Mediterranean diet (MedDiet), and ii) grey matter density (GMD) of brain regions associated with valuation and dietary self-regulation, the ventromedial (vmPFC) and dorsolateral prefrontal cortex (dlPFC), through voxel-based morphometry. Healthy food choices were ascertained through the Mediterranean Diet Adherence Screener (MEDAS) where higher scores indicated greater adherence to the MedDiet. Voxel-based morphometry showed that greater grey matter density in the dlPFC and vmPFC associated with a higher adherence to the MedDiet. These results replicate previous links between dietary decision-making measured under laboratory conditions and the neuroanatomy of the brain's valuation and self-control system. Importantly, they shed new light on the potential relevance of inter-individual differences in the neuroanatomy of these two brain regions for adhering to healthier dietary patterns in everyday life.

Placebo effects, in which a patient’s symptoms and subjective well-being improve in response to an inactive treatment, medication, or intervention (a placebo), are well known in clinical research. Basic research in human cognition and neuroscience has shown that these effects are linked to prognostic expectations of effectiveness and to recruitment of prefrontal cortex regions, including the medial (mPFC), ventromedial (vmPFC), and dorsolateral prefrontal cortex (dlPFC). However, how these expectations influence intrinsic resting-state brain connectivity remains unclear. Here, we conducted seed-based resting-state functional connectivity analyses in 60 healthy, fasting female participants undergoing a placebo intervention that induced hunger expectations. In line with previously published results, the intervention induced hunger expectations and biased hunger sensations. We found that decreased hunger expectations attenuated mPFC-angular gyrus connectivity within the default mode network, while increased hunger expectations reduced vmPFC-dlPFC connectivity and enhanced dlPFC-thalamus coupling within frontoparietal and interoceptive networks. These results suggest that placebo-induced hunger expectations modulate prefrontal cortex connections with regions involved in valuation, cognitive control, and interoception. This modulation may reflect neural mechanisms by which beliefs shape bodily sensations under placebo conditions, advancing understanding of the neural substrates of expectation-driven sensory experiences. Highlights: ◻ Decreased-hunger expectations attenuate mPFC–angular gyrus connectivity. ◻ Increased-hunger expectations attenuate vmPFC–dlPFC connectivity. ◻ Increased-hunger expectations strengthen dlPFC–thalamus connectivity.