Mediterranean diet and brain functional connectivity in a population without dementia

Abstract

Introduction: Adjustable lifestyle factors, such as diet, are associated with cognitive functions, structural and functional brain measures, but the association between the functional connectivity (FC) and the Mediterranean Diet (Medicine) in population without dementia is yet to be explored.

Methods: The association between MeDi and brain FC in 105 individuals without dementia aged 63 (SD ± 8.72) years old who underwent brain MRI including resting-state (rs) functional MRI (fMRI) was examined. Dietary intake was evaluated through four 24-h recalls using the multiple-pass method and adherence to the MeDi was estimated using the MedDietScore, with higher values indicating greater adherence to MeDi. Multivariable linear regression models were used to investigate the associations between FC (both positive and negative associations) and MedDietScore.

Results: Rs-fMRI analysis revealed significant associations between FC and MedDietScore. The FC between the medial prefrontal cortex and a cluster located in left postcentral gyrus and in the left supramarginal gyrus was positively associated with MedDietScore. On the other hand, the FC between medial visual and right posterior division of both middle and superior temporal gyrus was negatively associated with MedDietScore. Of note, a temporal negative correlation was detected between above-mentioned FC networks. The FC between superior temporal gyrus and occipital regions was associated with participants' attention, executive functions, and memory scores. Furthermore, the associations for attention and executive functions were pronounced in participants with high adherence to MeDi compared to those with low adherence to MeDi.

Discussion: In conclusion, our study documented an association between higher adherence to MeDi and rs-FC in fronto-parietal and temporo-occipital regions, particularly in areas that are involved in cognitive processes altered across normal and pathological aging. From a clinical point of view, our findings support a favorable role of MeDi on FC which may have significant clinical implications in the rapidly aging population. Rs-fMRI is also proposed as a useful tool in the emerging field of nutritional neuroscience and a candidate non-invasive biomarker of brain aging.

Keywords: aging; biomarkers; functional connectivity; mediterranean diet; rs-fMRI.

Figure 1

Anatomical regions (left postcentral gyrus, left anterior division of supramarginal gyrus) whose negative functional connectivity to the medial prefrontal cortex (A) positively correlates with MedDietScore (B). Connectivity index indicates the correlation between the BOLD signal of seed region (medial prefrontal cortex) and the BOLD signal of the left postcentral gyrus, left anterior division of supramarginal gyrus. R² indicates the proportion of variance in FC explained by the MedDietScore. ROI, region of interest; FC, functional connectivity; L, left; pCG, posterior cingulate gyrus; aSMG, anterior division of supramarginal gyrus; MedDietScore, Mediterranean Diet Score; MeDi, Mediterranean Diet.

Figure 2

Anatomical regions (right posterior middle temporal gyrus, right posterior superior temporal gyrus) whose negative functional connectivity to the medial visual cortex (A) negatively correlates with MedDietScore (B). Connectivity index indicates the correlation between the BOLD signal of seed region (medial visual cortex) and the BOLD signal of the right postserior middle temporal gyrus, right posterior superior temporal gyrus. R² indicates the proportion of variance in FC explained by the MedDietScore. ROI, region of interest; FC, functional connectivity; R, right; pMTG, posterior middle temporal gyrus; pSTG, posterior superior temporal gyrus; MedDietScore, Mediterranean Diet Score; MeDi, Mediterranean Diet.

Figure 3

Anatomical regions (right occipital pole) whose negative FC to the right posterior superior temporal gyrus (A) negatively correlates with MedDietScore (B). Connectivity index indicates the correlation between the BOLD signal of seed region (right posterior superior temporal gyrus) and the BOLD signal of the right occipital pole. R² indicates the proportion of variance in FC explained by the MedDietScore. ROI, region of interest; FC, functional connectivity; R, right; OP, occipital pole; MedDietScore, Mediterranean Diet Score; MeDi, Mediterranean Diet.

Figure 4

Interaction between the effect of MeDi group and rs-FC of right posterior segment of superior temporal gyrus and right occipital pole on (A) attention and (B) executive functions. MeDi groups were defined based on the median MedDietScore of the group and all participants were considered as participants with low and high adherence to MeDi. MeDi, Mediterranean diet; rs-FC, resting-state functional connectivity; RpSTG, right posterior segment of the superior temporal gyrus; ROP, right occipital pole.