Effects of Smoking on Regional Homogeneity in Mild Cognitive Impairment: A Resting-State Functional MRI Study

Different stimulation targets of rTMS modulate specific triple-network and hippocampal-cortex functional connectivity

BACKGROUND

Repetitive transcranial magnetic stimulation (rTMS) is widely applied to treat Alzheimer's disease (AD). Various treatment targets are currently being explored in clinical research. However, target diversity can result in considerable heterogeneity.

OBJECTIVE

This study aimed to investigate whether different rTMS targets can enhance cognitive domains by modulating functional connectivity (FC) of the hippocampus (HIP) and triple network, which comprises the salience network (SN), central executive network (CEN), and default mode network (DMN).

METHODS

We enrolled 63 patients with AD, of whom 48 and 15 underwent rTMS targeting the left dorsolateral prefrontal cortex (dlPFC) and the bilateral angular gyrus (ANG), respectively. We examined the network-level FC differences within the triple-network before and after treatment. Additionally, we utilized HIP as a seed for voxel-level analysis. We compared the similarities and differences in the effects of dlPFC and ANG rTMS.

RESULTS

rTMS targeting the dlPFC primarily influenced the FC of the CEN, whereas rTMS targeting the ANG primarily influenced the SN and DMN. Moreover, the right temporal lobe within the DMN exhibited reduced FC with the left HIP following both therapies. The results of least absolute shrinkage and selection operator (LASSO) analysis indicated that hippocampal-cortex FC played a dominant role in the therapeutic effect. The observed FC changes significantly correlated with improvements in multiple cognitive scales.

CONCLUSION

rTMS targeting different regions affected the FC of specific networks. Both stimulation targets modulate the FC of hippocampal-cortex to influence therapeutic outcomes. Classification of patients based on damaged networks can further inform subsequent treatment strategies.

Urinary nicotine metabolites are associated with cognitive impairment among the elderly in southern China

INTRODUCTION

This study comprehensively assessed the association between eight metabolites of urinary nicotine and cognitive impairment.

METHODS

This cross-sectional study was based on the data of Shenzhen Aging Related Disorder Cohort (SADC), including 51 elderly community data variables such as demographic characteristics, neuropsychological assessment and environmental factors, from July 2017 to November 2018. Participant's cognitive function was assessed by Mini-Mental State Examination (MMSE) scale and urinary nicotine metabolite [including cotinine N-β-D-glucuronide (CotGluc), rac 4-hydroxy-4-(3-pyridyl) butanoic acid dicyclohexylamine salt (HyPyBut), trans-3'-hydroxy cotinine O-β-D-glucuronide (OHCotGluc), and cotinine (Cot), etc.] concentrations were measured by high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). Generalized linear models and restricted cubic spline models were used to explore the relationships between the urinary levels of nicotine metabolite and cognitive function.

RESULTS

A total of 296 individuals aged >60 years were included. Individuals in the third quartile of CotGluc had a 0.786 point (95% CI: -1.244 - -0.329) decrease or in the highest quartile of OHCotGluc had a 0.804 point (95% CI: -1.330 - -0.278) decreased in attention and calculation compared to those in the lowest quartile (all p for trend <0.05). Compared with those in the lowest quartile, individuals in the highest quartile of CotGluc, HyPyBut, OHCotGluc and Cot, respectively, corresponded to a 1.043 point (95% CI: -2.269-0.182), 1.101 points (95% CI: -2.391-0.188), 2.318 points (95% CI: -3.615 - -1.020), and 1.460 points (95% CI: -2.726 - -0.194) decreased in MMSE total score (all p for trend <0.05). A non-linear dose-response relationship between urinary levels of CotGluc, HyPyBut, OHCotGluc or Cot and cognitive function (all overall p<0.05, non-linear p<0.05). Subgroup analysis showed that urinary levels of CotGluc, OHCotGluc or Cot were significantly negatively associated with cognitive function (all p for trend <0.05) among females and non-smokers.

CONCLUSIONS

The findings highlight the public health implications of environmental tobacco smoke exposure, and effective interventions need to be performed for vulnerable populations.

Functional MRI-specific alterations in frontoparietal network in mild cognitive impairment: an ALE meta-analysis

Background

Mild cognitive impairment (MCI) depicts a transitory phase between healthy elderly and the onset of Alzheimer's disease (AD) with worsening cognitive impairment. Some functional MRI (fMRI) research indicated that the frontoparietal network (FPN) could be an essential part of the pathophysiological mechanism of MCI. However, damaged FPN regions were not consistently reported, especially their interactions with other brain networks. We assessed the fMRI-specific anomalies of the FPN in MCI by analyzing brain regions with functional alterations.

Methods

PubMed, Embase, and Web of Science were searched to screen neuroimaging studies exploring brain function alterations in the FPN in MCI using fMRI-related indexes, including the amplitude of low-frequency fluctuation, regional homogeneity, and functional connectivity. We integrated distinctive coordinates by activating likelihood estimation, visualizing abnormal functional regions, and concluding functional alterations of the FPN.

Results

We selected 29 studies and found specific changes in some brain regions of the FPN. These included the bilateral dorsolateral prefrontal cortex, insula, precuneus cortex, anterior cingulate cortex, inferior parietal lobule, middle temporal gyrus, superior frontal gyrus, and parahippocampal gyrus. Any abnormal alterations in these regions depicted interactions between the FPN and other networks.

Conclusion

The study demonstrates specific fMRI neuroimaging alterations in brain regions of the FPN in MCI patients. This could provide a new perspective on identifying early-stage patients with targeted treatment programs.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023432042, identifier: CRD42023432042.

Convergent and distinct neural structural and functional patterns of mild cognitive impairment: a multimodal meta-analysis

Mild cognitive impairment (MCI) is regarded as a transitional stage between normal aging and Alzheimer's disease. Numerous voxel-based morphometry (VBM) and resting-state fMRI (rs-fMRI) studies have provided strong evidence of abnormalities in the structure and intrinsic function of brain regions in MCI. Studies have recently begun to explore their association but have not employed systematic information in this pursuit. Herein, a multimodal meta-analysis was performed, which included 43 VBM datasets (1,247 patients and 1,352 controls) of gray matter volume (GMV) and 42 rs-fMRI datasets (1,468 patients and 1,605 controls) that combined 3 metrics: amplitude of low-frequency fluctuation, the fractional amplitude of low-frequency fluctuation, and regional homogeneity. Compared to controls, patients with MCI displayed convergent reduced regional GMV and altered intrinsic activity, mainly in the default mode network and salience network. Decreased GMV alone in ventral medial prefrontal cortex and altered intrinsic function alone in bilateral dorsal anterior cingulate/paracingulate gyri, right lingual gyrus, and cerebellum were identified, respectively. This meta-analysis investigated complex patterns of convergent and distinct brain alterations impacting different neural networks in MCI patients, which contributes to a further understanding of the pathophysiology of MCI.

Interactions between cigarette smoking and cognitive status on functional connectivity of the cortico-striatal circuits in individuals without dementia: A resting-state functional MRI study

Aims

Cigarette smoking is a modifiable risk factor for Alzheimer's disease (AD), and controlling risk factors may curb the progression of AD. However, the underlying neural mechanisms of the effects of smoking on cognition remain largely unclear. Therefore, we aimed to explore the interaction effects of smoking × cognitive status on cortico‐striatal circuits, which play a crucial role in addiction and cognition, in individuals without dementia.

Methods

We enrolled 304 cognitively normal (CN) non‐smokers, 44 CN smokers, 130 mild cognitive impairment (MCI) non‐smokers, and 33 MCI smokers. The mixed‐effect analysis was performed to explore the interaction effects between smoking and cognitive status (CN vs. MCI) based on functional connectivity (FC) of the striatal subregions (caudate, putamen, and nucleus accumbens [NAc]).

Results

The significant interaction effects of smoking × cognitive status on FC of the striatal subregions were detected in the left inferior parietal lobule (IPL), bilateral cuneus, and bilateral anterior cingulate cortex (ACC). Specifically, increased FC of right caudate to left IPL was found in CN smokers compared with non‐smokers. The MCI smokers showed decreased FC of right caudate to left IPL and of right putamen to bilateral cuneus and increased FC of bilateral NAc to bilateral ACC compared with CN smokers and MCI non‐smokers. Furthermore, a positive correlation between FC of the NAc to ACC with language and memory was detected in MCI smokers.

Conclusions

Cigarette smoking could affect the function of cortico‐striatal circuits in patients with MCI. Our findings suggest that quitting smoking in the prodromal stage of AD may have the potential to prevent disease progression.