Increased subcortical neural activity among HIV+ individuals during a lexical retrieval task

Reversible large-scale network disruption correlates with neurocognitive improvement in HIV-associated minor neurocognitive disorder with combined anti-retroviral therapy intensification: a prospective longitudinal resting-state functional magnetic resonance imaging study

OBJECTIVE

HIV-associated neurocognitive disorder (HAND) affects multiple cognitive domains and currently, the neuropsychological testing is the gold standard to identify these deficits. The aim of this longitudinal 12-month pilot study is to determine the effect of intensified combination antiretroviral therapy (cART) on rs-fMRI in virally suppressed (both in CSF and blood) patients with active HAND (those who have progressive neurocognitive impairment) and correlated with neurocognitive function tests.

METHODS

In this pilot study, we have evaluated sixteen patients with active HAND with viral suppression in both blood and CSF to study the effect of cART on functional connectivity. Participants underwent rs-fMRI at the baseline (time point-1 (TP-1) and 12-month visits (time point-2 (TP-2)). Connectivity in the five major networks was measured at TP-1 and TP-2 using the seed-based approach. All the participants underwent a five-domain neuropsychological battery at TP-1 and TP-2. Neurocognitive scores (NC) as well as blood and CSF markers were correlated with functional connectivity (FC).

RESULTS

There was a significant increase in the FC between the two time points within the executive, salience, default mode, dorsal attention, and visual networks at voxel level threshold of p < 0.001 and cluster level threshold of p < 0.05 and corrected for false detection rate (FDR). The neurocognitive scores were positively correlated with all the networks at similar cluster and voxel level thresholds.

CONCLUSIONS

These results indicate that rs-fMRI can be potentially used as one of the biomarkers for treatment efficacy in HAND.

Brain Volumetric Alterations in Preclinical HIV-Associated Neurocognitive Disorder Using Automatic Brain Quantification and Segmentation Tool

Purpose

This study aimed to determine if people living with HIV (PLWH) in preclinical human immunodeficiency virus (HIV)-associated neurocognitive disorder (HAND), with no clinical symptoms and without decreased daily functioning, suffer from brain volumetric alterations and its patterns.

Method

Fifty-nine male PLWH at the HAND preclinical stage were evaluated, including 19 subjects with asymptomatic neurocognitive impairment (ANI), 17 subjects with cognitive abnormality that does not reach ANI (Not reach ANI), and 23 subjects with cognitive integrity. Moreover, 23 healthy volunteers were set as the seronegative normal controls (NCs). These individuals underwent sagittal three-dimensional T₁-weighted imaging (3D T₁WI). Quantified data and volumetric measures of brain structures were automatically segmented and extracted using AccuBrain^®. In addition, the multiple linear regression analysis was performed to analyze the relationship of volumes of brain structures and clinical variables in preclinical HAND, and the correlations of the brain volume parameters with different cognitive function states were assessed by Pearson's correlation analysis.

Results

The significant difference was shown in the relative volumes of the ventricular system, bilateral lateral ventricle, thalamus, caudate, and left parietal lobe gray matter between the preclinical HAND and NCs. Furthermore, the relative volumes of the bilateral thalamus in preclinical HAND were negatively correlated with attention/working memory (left: r = -0.271, p = 0.042; right: r = -0.273, p = 0.040). Higher age was associated with increased relative volumes of the bilateral lateral ventricle and ventricular system and reduced relative volumes of the left thalamus and parietal lobe gray matter. The lower CD4⁺/CD8⁺ ratio was associated with increased relative volumes of the left lateral ventricle and ventricular system. Longer disease course was associated with increased relative volumes of the bilateral thalamus. No significant difference was found among preclinical HAND subgroups in all indices, and the difference between the individual groups (Not reach ANI and Cognitive integrity groups) and NCs was also insignificant. However, there was a significant difference between ANI and NCs in the relative volumes of the bilateral caudate and lateral ventricle.

Conclusion

Male PLWH at the HAND preclinical stage suffer from brain volumetric alterations. AccuBrain^® provides potential value in evaluating HIV-related neurocognitive dysfunction.

Cognitive Trajectory Phenotypes in Human Immunodeficiency Virus-Infected Patients

OBJECTIVE

The presentation of cognitive impairments in HIV-infected individuals has transformed since the introduction of antiretroviral therapies. Although the overall prevalence of cognitive impairments has not changed considerably, frank dementia is now infrequent, and milder forms of cognitive impairments predominate. Mechanistic insights to the underlying causes of these residual cognitive impairments have been elusive, in part due to the heterogenous etiology of cognitive dysfunction in this population. Here, we sought to categorize longitudinal change in HIV-infected patients based on the performance in specific cognitive domains.

DESIGN

This study consisted of 193 participants from the CHARTER cohort with detailed demographic, clinical, and neuropsychological testing data obtained from 2 study visits interspersed by ∼6 months. Cognitive testing assessed executive function, learning and delayed recall, working memory, verbal fluency, speed of information processing, and motor skills. Change scores were calculated for each domain between the 2 study visits. Dimension reduction and clustering was accomplished by principal component analysis of change scores and k-means clustering to identify cognitive domains that group together and groups of subjects with similar patterns of change.

RESULTS

We identified 4 distinct cognitive change phenotypes that included declines in: (1) verbal fluency, (2) executive function (3) learning and recall, and (4) motor function, with approximately equal numbers of participants in each phenotype.

CONCLUSIONS

Each of the 4 cognitive change phenotypes identify deficits that imply perturbations in specific neural networks. Future studies will need to validate if cognitive change phenotypes are associated with alterations in associated neural pathways.

Effects of early HIV infection and combination antiretroviral therapy on intrinsic brain activity: a cross-sectional resting-state fMRI study

Objective: To investigate effects of early HIV infection and combination antiretroviral therapy (cART) on intrinsic brain activity by using amplitude of low-frequency fluctuation (ALFF) analysis. Patients and methods: Forty-nine HIV patients, including 26 with cART (HIV+/cART+) and 23 treatment-naïve (HIV+/cART-), and 25 matched healthy controls (HCs) underwent resting-state functional magnetic resonance imaging examination. ALFF values were compared by using one-way ANOVA tests with Analysis of Functional NeuroImages (AFNI)'s 3dClustSim correction (voxel p<0.005, α<0.05). In addition, the ALFF values of brain regions that showed significant differences among the three groups were correlated with clinical and neuropsychological variables in both groups of patients by using Spearman correlation analysis. Results: ANOVA analysis showed that statistic difference of ALFF values among three groups was located in the occipital cortex. Post hoc analysis showed a decrease in occipital ALFF value in HIV patients compared to HC, but showed no difference of occipital ALFF between HIV+/cART+ and HIV+/cART-. Additionally, compared with HC, HIV+/cART+ exhibited higher ALFF in the right caudate and frontoparietal cortex, and HIV+/cART- showed higher ALFF in the bilateral caudate. HIV+/cART+ demonstrated higher ALFF values in auditory cortex than HIV+/cART-. Moreover, ALFF values in the right occipital cortex were positively associated with CD4⁺/CD8⁺ ratio and executive function in HIV+/cART-. Conclusion: Early HIV-infected individuals presented reduced spontaneous brain activity in the occipital cortex. cART appeared to be ineffective in halting the HIV-induced neurodegeneration but might delay the progression of neural dysfunction to some extent. ALFF might be a potential biomarker in monitoring the effects of HIV and cART on brain function.

Increased posterior cingulate cortex efficiency may predict cognitive impairment in asymptomatic HIV patients

Purpose Despite antiretroviral therapy, approximately half of individuals with human immunodeficiency virus (HIV) will develop HIV-associated neurocognitive disorder (HAND). Efficiency of brain networks is of great importance for cognitive functioning, since functional networks may reorganize or compensate to preserve normal cognition. This study aims to compare efficiency of the posterior cingulate cortex (PCC) between patients with and without HAND and controls. We hypothesize HAND negative (HAND-) patients will show higher PCC efficiency than HAND positive (HAND+) patients. Methods A total of 10 HAND + patients were compared with 9 HAND- patients and 17 gender-, age-, and education-matched controls. Resting-state functional MRI was acquired with a 3 Tesla scanner. Local efficiency, a measure of network functioning, was investigated for PCC. Network differences among HAND + , HAND- patients and controls were tested as well as correlations between network parameters and cognitive test performance in different domains. Results HAND- patients showed significantly increased PCC efficiency compared with healthy controls ( p = 0.015). No differences were observed between HAND + patients and either controls ( p = 0.327) or HAND- patients ( p = 0.152). In HAND- patients, PCC efficiency was positively related with cognitive performance in the attention/working memory domain ( p = 0.003). Conversely, in HAND + patients, PCC efficiency was negatively correlated with performance in the abstraction/executive domain ( p = 0.002). Conclusion HAND- patients showed a higher level of PCC efficiency compared with healthy subjects, and PCC efficiency was positively related to cognitive performance. These results support the functional reorganization hypothesis, that increased PCC efficiency is a compensation technique to maintain cognitive functioning.

Resting-state subcortical functional connectivity in HIV-infected patients on long-term cART

Despite long-term successful treatment with cART, impairments in cognitive functioning are still being reported in HIV-infected patients. Since changes in cognitive function may be preceded by subtle changes in brain function, neuroimaging techniques, such as resting-state functional magnetic resonance imaging (rs-fMRI) have become useful tools in assessing HIV-associated abnormalities in the brain. The purpose of the current study was to examine the extent to which HIV infection in virologically suppressed patients is associated with disruptions in subcortical regions of the brain in comparison to a matched HIV-negative control group. The sample consisted of 72 patients and 39 controls included between January 2012 and January 2014. Resting state functional connectivity was determined between fourteen regions-of-interest (ROI): the left and right nucleus accumbens, amygdala, caudate nucleus, hippocampus, putamen, pallidum and thalamus. A Bayesian method was used to estimate resting-state functional connectivity, quantified in terms of partial correlations. Both groups showed the strongest partial correlations between the left and right caudate nucleus and the left and right thalamus. However, no differences between the HIV patients and controls were found between the posterior expected network densities (control network density = 0.26, SD = 0.05, patient network density = 0.26, SD = 0.04, p = 0.58). The results of the current study show that HIV does not affect subcortical connectivity in virologically controlled patients who are otherwise healthy.

Imaging studies of the HIV-infected brain

Human immunodeficiency virus (HIV) enters the brain early after infecting humans and may remain in the central nervous system despite successful antiretroviral treatment. Many neuroimaging techniques were used to study HIV+ patients with or without opportunistic infections. These techniques assessed abnormalities in brain structures (using computed tomography, structural magnetic resonance imaging (MRI), diffusion MRI) and function (using functional MRI at rest or during a task, and perfusion MRI with or without a contrast agent). In addition, single-photon emission computed tomography with various tracers (e.g., thallium-201, Tc99-HMPAO) and positron emission tomography with various agents (e.g., [18F]-dexoyglucose, [11C]-PiB, and [11C]-TSPO tracers), were applied to study opportunistic infections or HIV-associated neurocognitive disorders. Neuroimaging provides diagnoses and biomarkers to quantitate the severity of brain injury or to monitor treatment effects, and may yield insights into the pathophysiology of HIV infection. As the majority of antiretroviral-stable HIV+ patients are living longer, age-related comorbid disorders (e.g., additional neuroinflammation, cerebrovascular disorders, or other dementias) will need to be considered. Other highly prevalent conditions, such as substance use disorders, psychiatric illnesses, and the long-term effects of combined antiretroviral therapy, all may lead to additional brain injury. Neuroimaging studies could provide knowledge regarding how these comorbid conditions impact the HIV-infected brain. Lastly, specific molecular imaging agents may be needed to assess the central nervous system viral reservoir.