Altered Global Signal Topography in Alcohol Use Disorders

Studying cognition impairment in patients with minimal hepatic encephalopathy through functional connectivity analysis: evidence from resting-state functional MRI

AIM

This study aimed to investigate functional connectivity (FC) alterations between the insula and other brain regions in minimal hepatic encephalopathy (MHE) patients and their association with cognitive deficits.

MATERIALS AND METHODS

The study included 23 MHE patients and 25 healthy control (HC) individuals. All participants underwent resting-state functional magnetic resonanceimaging (fMRI), neuropsychological testing, and cognitive scale assessments. FC analysis was performed to investigate the connectivity between the insula and the whole brain in the context of MHE. Pearson correlation analysis was conducted to assess the association between changes in FC and cognitive scale scores.

RESULTS

The HC and MHE groups showed significant differences in cognitive performance measures, such as the Number Connection Test-A (NCT-A), Digit symbol Test (DST), and Montreal Cognitive Assessment (MoCA) score (P < 0.01). The MHE group demonstrated elevated FC between the right insula and the right superior frontal gyrus, right middle frontal gyrus, and right precentral gyrus compared with the HC group. Furthermore, the left insula showed increased FC with the left middle frontal gyrus and the right middle frontal gyrus (P < 0.05, corrected). Notably, these changes in FC among MHE patients were significantly correlated with the MoCA score (P < 0.05, corrected).

CONCLUSION

This study emphasises the FC alterations between the insula and the prefrontal cortex in MHE patients, which have a close association with cognitive functions. FC could potentially serve as a biomarker for diagnosing and assessing the severity of cognitive impairments in MHE.

Systematic review on resting-state fMRI in people with AUD and people who binge drink

Resting-state functional magnetic resonance imaging (rsfMRI) has become ubiquitous in neuroimaging to study disorders, including alcohol use disorder (AUD), given its potential to serve as a biomarker of psychiatric symptoms. The number of techniques, sample heterogeneity, and findings demand the assessment of results to identify potential biomarkers for the development of treatment. This systematic review aimed to synthesize the alcohol rsfMRI literature by summarizing the results by analysis approach and groups to examine these findings in the context of the neurobiology of addiction model. Three databases were systematically searched, resulting in the inclusion of 17 studies with a total of 784 participants (387 were people with AUD, 38 engaged in binge drinking, and 359 were controls). Seed-based functional connectivity studies were the most prominent. Compared to controls, people who binge drink and people with AUD showed greater connectivity of the Middle Frontal Gyrus-a region associated with the preoccupation/anticipation stage of the theory. Regions of the prefrontal and limbic cortex were most consistently reported in studies. The different types of analyses, sample size, and variability in the sample may have contributed to differences reported across studies. This review synthesizes and examines the results of different studies using the neurobiology of addiction theory, which may inform future studies on potential regions of interest, recruitment approaches, and analysis methods. Standardizing the methods for such a heterogeneous population could lead to more rapid development of neurobiologically-informed treatments for AUD.

The altered functional connectivity density related to cognitive impairment in alcoholics

Alcohol use disorder (AUD) is one of the most common substance use disorders contributing to both behavioral and cognitive impairments in patients with AUD. Recent neuroimaging studies point out that AUD is a typical disorder featured by altered functional connectivity. However, the details about how voxel-wise functional coordination remain unknown. Here, we adopted a newly proposed method named functional connectivity density (FCD) to depict altered voxel-wise functional coordination in AUD. The novel functional imaging technique, FCD, provides a comprehensive analytical method for brain's “scale-free” networks. We applied resting-state functional MRI (rs-fMRI) toward subjects to obtain their FCD, including global FCD (gFCD), local FCD (lFCD), and long-range FCD (lrFCD). Sixty-one patients with AUD and 29 healthy controls (HC) were recruited, and patients with AUD were further divided into alcohol-related cognitive impairment group (ARCI, n = 11) and non-cognitive impairment group (AUD-NCI, n = 50). All subjects were asked to stay stationary during the scan in order to calculate the resting-state gFCD, lFCD, and lrFCD values, and further investigate the abnormal connectivity alterations among AUD-NCI, ARCI, and HC. Compared to HC, both AUD groups exhibited significantly altered gFCD in the left inferior occipital lobe, left calcarine, altered lFCD in right lingual, and altered lrFCD in ventromedial frontal gyrus (VMPFC). It is notable that gFCD of the ARCI group was found to be significantly deviated from AUD-NCI and HC in left medial frontal gyrus, which changes probably contributed by the impairment in cognition. In addition, no significant differences in gFCD were found between ARCI and HC in left parahippocampal, while ARCI and HC were profoundly deviated from AUD-NCI, possibly reflecting a compensation of cognition impairment. Further analysis showed that within patients with AUD, gFCD values in left medial frontal gyrus are negatively correlated with MMSE scores, while lFCD values in left inferior occipital lobe are positively related to ADS scores. In conclusion, patients with AUD exhibited significantly altered functional connectivity patterns mainly in several left hemisphere brain regions, while patients with AUD with or without cognitive impairment also demonstrated intergroup FCD differences which correlated with symptom severity, and patients with AUD cognitive impairment would suffer less severe alcohol dependence. This difference in symptom severity probably served as a compensation for cognitive impairment, suggesting a difference in pathological pathways. These findings assisted future AUD studies by providing insight into possible pathological mechanisms.