Neuropsychological deficits in tests of executive function in asymptomatic and symptomatic HIV-1 seropositive men

A Rationale and Approach to the Development of Specific Treatments for HIV Associated Neurocognitive Impairment

Neurocognitive impairment (NCI) associated with HIV infection of the brain impacts a large proportion of people with HIV (PWH) regardless of antiretroviral therapy (ART). While the number of PWH and severe NCI has dropped considerably with the introduction of ART, the sole use of ART is not sufficient to prevent or arrest NCI in many PWH. As the HIV field continues to investigate cure strategies, adjunctive therapies are greatly needed. HIV imaging, cerebrospinal fluid, and pathological studies point to the presence of continual inflammation, and the presence of HIV RNA, DNA, and proteins in the brain despite ART. Clinical trials exploring potential adjunctive therapeutics for the treatment of HIV NCI over the last few decades have had limited success. Ideally, future research and development of novel compounds need to address both the HIV replication and neuroinflammation associated with HIV infection in the brain. Brain mononuclear phagocytes (MPs) are the primary instigators of inflammation and HIV protein expression; therefore, adjunctive treatments that act on MPs, such as immunomodulating agents, look promising. In this review, we will highlight recent developments of innovative therapies and discuss future approaches for HIV NCI treatment.

HIV Transgenic Rats Demonstrate Impaired Sensorimotor Gating But Are Insensitive to Cannabinoid (Δ9-Tetrahydrocannabinol)-Induced Deficits

BACKGROUND

HIV-associated neurocognitive disorder (HAND) is commonly observed in persons living with HIV (PWH) and is characterized by cognitive deficits implicating disruptions of fronto-striatal neurocircuitry. Such circuitry is also susceptible to alteration by cannabis and other drugs of abuse. PWH use cannabis at much higher rates than the general population, thus prioritizing the characterization of any interactions between HIV and cannabinoids on cognitively relevant systems. Prepulse inhibition (PPI) of the startle response, the process by which the motor response to a startling stimulus is attenuated by perception of a preceding non-startling stimulus, is an operational assay of fronto-striatal circuit integrity that is translatable across species. PPI is reduced in PWH. The HIV transgenic (HIVtg) rat model of HIV infection mimics numerous aspects of HAND, although to date the PPI deficit observed in PWH has yet to be fully recreated in animals.

METHODS

PPI was measured in male and female HIVtg rats and wild-type controls following acute, nonconcurrent treatment with the primary constituents of cannabis: Δ 9-tetrahydrocannabinol (THC; 1 and 3 mg/kg, s.c.) and cannabidiol (1, 10, and 30 mg/kg, i.p.).

RESULTS

HIVtg rats exhibited a significant PPI deficit relative to wild-type controls. THC reduced PPI in controls but not HIVtg rats. Cannabidiol exerted only minor, genotype-independent effects on PPI.

CONCLUSIONS

HIVtg rats exhibit a relative insensitivity to the deleterious effects of THC on the fronto-striatal function reflected by PPI, which may partially explain the higher rates of cannabis use among PWH.

Review of functional MRI in HIV: effects of aging and medication

HIV-associated neurocognitive disorder (HAND) is a frequently occurring comorbidity of HIV infection. Evidence suggests this condition starts subclinical before a progression to a symptomatic stage. Blood oxygenated level dependent (BOLD) fMRI has shown to be a sensitive tool to detect abnormal brain function in an early stage and might therefore be useful to evaluate the effect of HIV infection on brain function. An extensive literature search was performed in June 2015. Eligibility criteria for included studies were as follows: (1) conducting with HIV-positive patients, (2) using BOLD fMRI, and (3) including a HIV-negative control group. A total of 19 studies were included in the review including 931 participants. Differences in activation between HIV-positive and -negative participants were found when testing multiple domains, i.e., attention, (working) memory, and especially executive functioning. Overall, HIV-positive patients showed hyperactivation in task-related brain regions despite equal performances as controls. Task performance was degraded only for the most complex tasks. A few studies investigated the effect of aging on fMRI, and most of them found no interaction with HIV infection. Only three studies evaluated the effect of combination antiretroviral therapy (cART) on functional data suggesting an increase in activation with the use of cART. fMRI is a sensitive instrument to detect subtle cognitive changes in HIV patients. Open questions remain regarding the effects of cART on fMRI and the effects of aging on fMRI.

Interdisciplinary Differential Diagnosis and Care of a Patient with Atypical Delusional Parasitosis due to early HIV-related Dementia

OBJECTIVE

To provide a differential diagnosis and recommendations for care for an individual with suspected delusional parasitosis secondary to human immunodeficiency virus (HIV).

METHOD

A 62-year-old male with sexually acquired, chronic, and well-managed HIV infection was referred for neuropsychological evaluation and treatment recommendations following extensive self-manipulation of a sternoclavicular cystic mass and superficial skin lesions over most of his body. The patient reported that he had pulled long calcified tendrils out of the mass over a period of several weeks and that "encapsulated fat" was flowing beneath his skin.

RESULTS

Numerous lab panels were negative for any acute medical pathology. Clinical neuroimaging was unremarkable. Neuropsychological evaluation revealed a profile consistent with mild neurocognitive disorder due to HIV. Medical and behavioral recommendations were made for the management of delusional thought processes consistent with atypical delusional parasitosis and other symptoms. The patient was responsive to carefully crafted provider feedback and his delusional and somatic symptoms decreased significantly with risperidone.

CONCLUSIONS

This case illustrates the utility of neuropsychological assessment and provider feedback in the diagnosis and care of HIV-related neurocognitive disorder, the context of a delusional disorder.

Quantitative MRI Measures in SIV-Infected Macaque Brains

Multiple MRI modalities including Diffusion Tensor Imaging (DTI), perfusion MRI, in vivo MR Spectroscopy (MRS), volumetric MRI, contrast-enhanced MRI, and functional MRI have demonstrated abnormalities of the structural and functional integrity as well as neurochemical alterations of the HIV-infected central nervous system (CNS). MRI has been proposed as a robust imaging approach for the characterization of the stage of progression in HIV infection. However, the interpretation of the MRI findings of HIV patients is complicated by the fact that these clinical studies cannot readily be controlled. Simian immunodeficiency virus (SIV) infected macaques exhibit neuropathological symptoms similar to those of HIV patients, and are an important model for studying the course of CNS infection, cognitive impairment, and neuropathology of HIV disease as well as treatment efficacy. MRI of non-human primates (NHPs) is of limited benefit on most clinical scanners operating at or below 1.5 Tesla because this low field strength does not produce high-quality images of the relatively small NHP brain. Contemporary high field MRI (3T or more) for clinical use provides impressive sensitivity for magnetic resonance signal detection and is now accessible in many imaging centers and hospitals, facilitating the use of various MRI techniques in NHP studies. In this article, several high field MRI techniques and applications in macaque models of neuroAIDS are reviewed and the relation between quantitative MRI measures and blood T-cell alterations is discussed.

Planning deficits in HIV-associated neurocognitive disorders: component processes, cognitive correlates, and implications for everyday functioning

Executive dysfunction remains among the most prevalent cognitive domains impaired in persons with HIV-associated neurocognitive disorders (HAND). However, little is known specifically about the cognitive architecture or everyday functioning implications of planning, which is an aspect of executive functions involving the identification, organization, and completion of sequential behaviours toward the accomplishment of a goal. The current study examined these issues using the Tower of London(DX) in 53 individuals with HAND, 109 HIV-infected persons without HAND, and 82 seronegative participants. The HAND+ group performed significantly more poorly than HIV-infected individuals without HAND on number of correct moves, total moves, execution time, time violations, and rule violations. Within the HIV+ group as a whole, greater total move scores and rule violations were most strongly associated with executive dysfunction. Of clinical relevance, elevated total moves and rule violations were significant, independent predictors of self-reported declines in instrumental activities of daily living and unemployment status in HIV. These results suggest that planning accuracy, efficiency, and rule-bound control are impaired in HAND and may meaningfully affect more cognitively complex aspects of everyday living.

Longitudinal diffusion tensor imaging and perfusion MRI investigation in a macaque model of neuro-AIDS: a preliminary study

The Simian immunodeficiency virus (SIV) infected macaque model exhibits neuropathological symptoms similar to those of HIV(+) patients, and is ideal for studying cognitive impairment and neuropathological sequelae of disease in repeated measurements. The aim of this study is to use Diffusion Tensor Imaging (DTI) and perfusion MRI to longitudinally access the disease development in SIV-infected monkeys under controlled conditions and to cross-validate our finding with MRI studies in HIV(+) patients. Three adult male pig-tailed macaques (Macaca nemestrina) were inoculated with the SIVsmmFGb virus. Blood was collected for enumeration of CD4+ and CD8+ T-cells. Serial time-sensitive high-resolution T(2)- weighted structural images, Cerebral Blood Flow (CBF) maps measured with the Continuous Arterial Spin Labeling (CASL) technique, and DTI images were obtained. Animals were sacrificed after 24 weeks. Cognitive behavioral tests were also carried out at each time point. Longitudinal changes in brain volume, CBF, and DTI in selected regions were analyzed statistically. In this study, CD4+ T-cell counts were found declined significantly after SIV infection in all macaques. No significant neurological behavior and brain volume changes were observed following virus inoculation. The CBF was found reduced in the caudate, inferior parietal cortex, and the prefrontal cortex. Fractional Anisotropy (FA) values in the whole brain and several Regions of Interest (ROIs) decreased significantly. These longitudinal changes in CBF and FA are correlated with CD4+ T-cell depletion and/or CD4:CD8 ratio. The MRI findings from this pilot study agree with previous results in HIV(+) patients.

Methamphetamine and lentivirus interactions: reciprocal enhancement of central nervous system disease

Use of methamphetamine is increasingly a significant factor for the spread of human immunodeficiency virus type 1, for in certain populations, there is a convergence of methamphetamine abuse with human immunodeficiency virus type 1 infection. Methamphetamine and human immunodeficiency virus type 1 are both individually neuropathogenic, and the neuropathology caused by these two agents occurs in overlapping brain regions. However, the biological interaction of methamphetamine with lentiviruses remains unknown. Here, we investigate the effects of simultaneous exposure of these two agents on disease progression using the feline immunodeficiency virus model. The study models the bingeing methamphetamine user with sequential and repeated episodes of use, which were interrupted by periods of abstinence. Methamphetamine exposure significantly accelerated and enhanced the severity of the feline immunodeficiency virus model-induced central nervous system functional pathology, as measured in delays in brainstem auditory evoked potentials. Reciprocally, feline immunodeficiency virus enhanced the severity of the methamphetamine-induced effects on brain monoamine neurotransmitter and dopamine transporter levels. The results of this study indicate that a dual potentiation occurred. That is, methamphetamine enhanced feline immunodeficiency virus model-induced central nervous system disease and feline immunodeficiency virus model enhanced the toxic effects of methamphetamine, heralding a significant concern for those individuals that are exposed to both agents.

Variable patterns of neuropsychological performance in HIV-1 infection

Based upon prior findings with group means, a "prototypical pattern" of neuropsychological results with HIV infection has emerged: impaired executive functioning, motor skills, speed of information processing, and learning, with intact memory retention, most language skills, and visuospatial functioning. We examined neuropsychological results from 553 HIV+ adults to determine the number of patterns seen among individuals with HIV infection. Factor analysis of a relatively comprehensive neuropsychological battery identified 6 component factors: verbal memory (VeM), visual memory (ViM), processing speed (PS), attention/working memory (A/WM), executive function (EF), and motor (M). These factor scores were submitted to hierarchical cluster analysis, to determine the appropriate number of clusters or patterns in the cohort. Final cluster membership was then determined by K-means analysis, based on the Lange, Iverson, Senior, and Chelune (2002) method. A 6-cluster solution was found to be most appropriate. The definitions of the clusters were based upon ipsative scoring of factor scores to indicate relative strengths and weaknesses (independent of overall level of performance): Cluster 1: strong EF; Cluster 2: strong M, weak VeM and EF; Cluster 3: strong PS, weak ViM and EF; Cluster 4: strong VeM, weak M; Cluster 5: strong A/WM; Cluster 6: strong VeM, weak EF. Neuropsychological-impairment rates differed across clusters, but all 6 clusters contained substantial numbers of impaired and unimpaired individuals. Cluster membership was not explained by demographic variables or psychiatric or neuromedical confounds. Thus, there does not appear to be a single, prototypical pattern of neuropsychological impairment associated with HIV infection for this battery of representative neuropsychological tests.

Callosal Compromise Differentially Affects Conflict Processing and Attentional Allocation in Alcoholism, HIV, and Their Comorbidity

Diffusion tensor imaging was used to study the combined effects of HIV-infection and alcoholism (ALC) on corpus callosum (CC) integrity in relation to processes of attentional allocation and conflict resolution assessed by a novel Stroop Match-to-Sample task. We tested 16 ALC, 19 HIV, 20 subjects with combined disorder and 17 controls. In ALC, low fractional anisotropy and high mean diffusivity throughout the CC correlated with poor Stroop-match performance, i.e., when the cue-color matched the color of the Stroop stimulus. By contrast, in the two HIV groups DTI relations were restricted to the genu and poor Stroop-nonmatch performance, i.e., when the cue-color was in conflict with the Stroop stimulus color. These results suggest that disruption of callosal integrity in HIV-infection and alcoholism differentially affects regionally-selective interhemispheric-dependent attentional processing. We speculate that callosal degradation in these diseases curtails the opportunity for collaboration between the two hemispheres that contributes to normal performance in HIV or alcoholic patients with higher callosal integrity.

Copolymer-1 induces adaptive immune anti-inflammatory glial and neuroprotective responses in a murine model of HIV-1 encephalitis

Copolymer-1 (COP-1) elicits neuroprotective activities in a wide range of neurodegenerative disorders. This occurs, in part, by adaptive immune-mediated suppression of microglial inflammatory responses. Because HIV infection and immune activation of perivascular macrophages and microglia drive a metabolic encephalopathy, we reasoned that COP-1 could be developed as an adjunctive therapy for disease. To test this, we developed a novel animal model system that reflects HIV-1 encephalitis in rodents with both innate and adaptive arms of the immune system. Bone marrow-derived macrophages were infected with HIV-1/vesicular stomatitis-pseudotyped virus and stereotactically injected into the basal ganglia of syngeneic mice. HIV-1 pseudotyped with vesicular stomatitis virus envelope-infected bone marrow-derived macrophages induced significant neuroinflammation, including astrogliosis and microglial activation with subsequent neuronal damage. Importantly, COP-1 immunization reduced astro- and microgliosis while diminishing neurodegeneration. Hippocampal neurogenesis was, in part, restored. This paralleled reductions in proinflammatory cytokines, including TNF-alpha and IL-1beta, and inducible NO synthase, and increases in brain-derived neurotrophic factor. Ingress of Foxp3- and IL-4-expressing lymphocytes into brains of COP-1-immunized animals was observed. We conclude that COP-1 may warrant therapeutic consideration for HIV-1-associated cognitive impairments.

Verbal fluency in HIV infection: a meta-analytic review

Given the largely prefrontostriatal neuropathogenesis of HIV-associated neurobehavioral deficits, it is often presumed that HIV infection leads to greater impairment on letter versus category fluency. A meta-analysis of the HIV verbal fluency literature was conducted (k = 37, n = 7110) to assess this hypothesis and revealed generally small effect sizes for both letter and category fluency, which increased in magnitude with advancing HIV disease severity. Across all studies, the mean effect size of category fluency was slightly larger than that of letter fluency. However, the discrepancy between category and letter fluency dissipated in a more conservative analysis of only those studies that included both tests. Thus, HIV-associated impairments in letter and category fluency are of similar magnitude, suggesting that mild word generation deficits are evident in HIV, regardless of whether traditional letter or semantic cues are used to guide the word search and retrieval process.

Impaired performance on the object retrieval-detour test of executive function in the SIV/macaque model of AIDS

NeuroAIDS, the neurological, motor, and cognitive impairments that occur in acquired immunodeficiency syndrome (AIDS) patients, is characterized by compromised function in frontal cortical and subcortical brain regions including impairments in motor control, reaction time, and executive functions. Executive function is a cognitive domain involving the regulation of behavior, including inhibitory control. The present study evaluated the effects of simian immunodeficiency virus (SIV) infection on the object retrieval detour (ORD) task to assess inhibitory control. The ORD task measures the ability to inhibit the prepotent response of reaching directly toward a food reinforcer placed in a transparent box. The box has one open side, and the animal must inhibit the initial reaching response and look to see which side is open. Subjects were 12 experimentally naive pigtailed macaques; six monkeys were infected with SIV. Baseline performance was compared to performance under "terminal" conditions (the week prior to the scheduled euthanasia) to determine if progression of SIV disease led to decreased ORD performance. SIV-infected monkeys acquired ORD performance at the same levels as uninfected control monkeys, and had similar latencies and error rates. However, in the terminal week there was a significant difference between the groups in the number of barrier reach errors (touching the side of the transparent box). Three individual SIV-infected monkeys were impaired on ORD performance both in terms of errors and speed of performance. Given the sensitivity of ORD performance to dopaminergic dysfunction, these results further implicate dopaminergic dysfunction as a mechanism of cognitive and motor impairments in NeuroAIDS.

Host response and dysfunction in the CNS during chronic simian immunodeficiency virus infection

CNS abnormalities can be detected during chronic human immunodeficiency virus (HIV) infection, before the development of opportunistic infections or other sequelae of immunodeficiency. However, although end-stage dementia caused by HIV has been linked to the presence of infected and activated macrophages and microglia in the brain, the nature of the changes resulting in the motor and cognitive disorders in the chronic stage is unknown. Using simian immunodeficiency virus-infected rhesus monkeys, we sought the molecular basis for CNS dysfunction. In the chronic stable stage, nearly 2 years after infection, all animals had verified CNS functional abnormalities. Both virus and infiltrating lymphocytes (CD8+ T-cells) were found in the brain. Molecular analysis revealed that the expression of several immune response genes was increased, including CCL5, which has pleiotropic effects on neurons as well as immune cells. CCL5 was significantly upregulated throughout the course of infection, and in the chronic phase was present in the infiltrating lymphocytes. We have identified an altered state of the CNS at an important stage of the viral-host interaction, likely arising to protect against the virus but in the long term leading to damaging processes.

Depression and neurocognitive performance in individuals with HIV/AIDS: 2-year follow-up

OBJECTIVES

The aims of this study were to follow a cohort of HIV-infected individuals for 2 years to assess changes in depression and neuropsychological performance over time, to explore the relationship between depression, HIV illness and neuropsychological performance, and to examine the natural history of the effect of highly active antiretroviral therapy (HAART) on depression and neurocognitive performance.

METHODS

HIV-seropositive out-patients were assessed at baseline and at 2-year follow-up. At each assessment, patients were assessed for depression [using the Beck Depression Inventory (BDI) and Structured Clinical Interview (SCID-CV)] and completed a battery of neuropsychological tests including the Cambridge Neuropsychological Test Automated Battery (CANTAB) and the Hopkins HIV Dementia Scale (HDS).

RESULTS

At baseline, 34.8% scored > or =14 on the BDI [> or =14 suggests depressive symptoms (DS)]. The SCID-CV revealed that 27% of participants met the criteria for current mood disorder. Seven per cent of the participants' scores on the HDS indicated HIV-associated cognitive changes. Eighty participants were re-tested at 2-year follow-up and were split into two groups based on BDI scores at baseline. CANTAB results revealed that the cohort were significantly impaired on nine of 10 measures compared with age-matched normative data. Neurocognitive performance significantly improved for participants with no DS at baseline, whereas participants with DS at baseline did not show as much improvement. Multivariate analysis revealed that 40% of the change in cognitive performance was attributable to the variables age, AIDS and HAART regimen.

CONCLUSION

These results suggest a significant decline in depression scores and an improvement in several neurocognitive domains over time, with a relationship between HIV illness, HAART, symptoms of depression and neurocognitive performance.

Prevalence, Course, and Risk Factors for Executive Impairment in Patients Hospitalized on a General Medicine Service

The purpose of this study was to determine the prevalence, course, and risk factors for executive impairment in patients hospitalized on a general medicine service. One hundred patients were administered the Executive Interview (EXIT25), the Executive Clock Drawing Task (CLOX), and the Mini-Mental State Examination at admission and discharge. Fifty-two percent of the patients at admission and 56% at discharge had scores indicating impairment on at least one measure of executive function. Median scores on every measure improved during hospitalization. Older patients and those with a cardiac or gastrointestinal disorder were more likely to have executive impairment. The prevalence of executive impairment on general medicine services is high. Although improvement in executive function occurs during hospitalization, many patients remained impaired.

Nature of depression in patients with HIV/AIDS

OBJECTIVE

Existing research suggests that the rate of depressive illness and depressive symptoms are high in people living with HIV/AIDS, but investigations on the causes of depression provide conflicting results. Social, psychological and biological factors have all been suggested as possible causes of depression in people living with HIV/AIDS. The suggestion that depression may be the result of the neurotropic effects of the virus on the central nervous system leading to an 'organic' or secondary depression has major implications in the treatment of HIV/AIDS. The aim of the current study was to further investigate the nature and underlying aetiology of depression in people living with HIV/AIDS.

METHOD

One hundred and twenty-nine people living with HIV/AIDS recruited for the study from outpatients clinics and primary care settings completed a range of self-report symptom measures including the Beck Depression Inventory (BDI), SF-36, SPHERE and a personality measure, the NEO Personality Inventory (NEO-PI). They also completed a battery of neuropsychological tests (CANTAB) and a structured clinical interview (SCID-DSM-IV). Medical and sociodemographic data were also recorded.

RESULTS

Approximately one-third scored > or = 14 on the BDI and 27% met criteria for a current 'mood disorder' on the SCID. Depressive symptoms were strongly related to personality style, having a past psychiatric history and current stressful psychosocial situation. There was no association between depression and HIV disease status. There was no evidence in this study cohort of a distinct subtype of 'organic' or secondary depression.

CONCLUSIONS

These results suggest that at least for 'well' people living with HIV/AIDS, there is no distinct subtype of depression and early treatment approaches can be modelled on those used for other non-HIV groups. Further longitudinal studies will be required to dissect out the multiple factors underlying depression in HIV/AIDS.

The stability of neurocognitive patterns in HIV infected men: classification considerations

For the neuropsychological impairment which takes place in HIV-1 infection, various classification systems, based on either neuropathological criteria, severity of the disorder or functional criteria, have been suggested in the literature. This study identifies the patterns of neurocognitive disorders in HIV-1 infection and investigates their stability at one-year follow-up. Two hundred and seventeen HIV-1-positive subjects in various stages of infection and 55 HIV-1-negative subjects were evaluated. Our results suggest that there is considerable diversity in the neuropsychological functioning of HIV patients but the patterns are relatively stable, functionally distinct, and differ with respect to the severity of the deficit. The overall pattern is consistent with existing neuropsychological knowledge on HIV infection. Comparison of the patterns identified in this study with other classification systems posed several problems, however, and these problems may have important implications for the theory and methodology of neuropsychological HIV research.

Differential effect of HIV infection and alcoholism on conflict processing, attentional allocation, and perceptual load: evidence from a Stroop Match-to-Sample task

BACKGROUND

Alcoholism and human immunodeficiency virus (HIV) infection each can impair components of selective attention, probably through disruption of the integrity of the frontoparietal neural systems that underlie conflict processing, attentional allocation, and perceptual load.

METHODS

We studied 18 patients with alcoholism (ALC) alone, 19 with HIV infection alone (HIV), 20 with both disorders (H+A), and 19 healthy control subjects (CTL). We used a novel paradigm (Stroop Match-to-Sample tasks), in which subjects saw either a valid or invalid color cue before a target word, printed in a color that was either congruent or incongruent with the word's meaning.

RESULTS

All groups showed a significant Stroop effect, cue-target color Match effect, and interaction between Match and Stroop, with an exaggerated Stroop effect for the Match condition. The HIV patients were comparable to CTL, whereas ALC showed mild delays, with further delays associated with comorbidity with HIV. Although H+A profited from a valid match to Stroop stimuli, they were compromised in disengaging attention from the invalidly cued color.

CONCLUSIONS

Impairment in conflict processing and attentional allocation in alcoholism suggests disruption of frontal-parietal attentional systems. Although HIV alone did not demonstrate detectable impairment in performance, HIV conferred liability on attentional processes when combined with alcohol abuse.

Impaired performance on a rhesus monkey neuropsychological testing battery following simian immunodeficiency virus infection

Infection with simian immunodeficiency virus (SIV) in macaques provides an excellent model of AIDS including HIV-induced central nervous system (CNS) pathology and cognitive/behavioral impairment. Recently a behavioral test battery has been developed for macaques based on the CANTAB human neuropsychological testing battery. As with human neuropsychological batteries, different tasks are thought to involve different neural substrates, and therefore performance profiles may assess function in particular brain regions. Ten rhesus monkeys were infected with SIV after being trained on two or more of the battery tasks addressing memory (delayed nonmatching to sample, DNMS), spatial working memory (using a self-ordered spatial search task, SOSS), motivation (progressive-ratio, PR), reaction time (RT), and/or fine motor skills (bimanual motor skill, BMS). Performance was compared to that of 9 uninfected monkeys. Overall, some aspect of performance was impaired in all 10 monkeys following infection. Consistent with results in human AIDS patients, individual performance was impaired most often on battery tasks thought to be sensitive to frontostriatal dopaminergic functioning such as SOSS, RT, and BMS. These results further demonstrate the similarity of behavioral impairment produced by SIV and HIV on homologous behavioral tests, and establish the utility of the testing battery for further investigations into the CNS mechanisms of the reported behavioral changes.

Cognitive complaints, depression, medical symptoms, and their association with neuropsychological functioning in HIV infection: a structural equation model analysis

The main objective of this study was to use structural equation modeling (SEM) to clarify the relationship between subjective cognitive complaints and neuropsychological functioning in 160 adults with HIV infection. Participants completed questionnaires assessing cognitive complaints, symptoms of depression, and HIV-related medical symptoms. Neuropsychological tests included measures of attention, verbal fluency, psychomotor skills, learning, memory, and executive skills. SEM was used to test models of the relationships among cognitive complaints, mood, and medical symptoms with neuropsychological functioning. The model indicated that although depressed mood (beta = 0.32, p < .01) and medical symptoms (beta = 0.31, p < .01) influenced cognitive complaints, cognitive complaints were independently associated with poorer neuropsychological performance (beta = 0.39, p < .01). Mood and medical symptoms were significantly correlated but were not significantly associated with neuropsychological skills.

Working memory performance predicts subjective cognitive complaints in HIV infection

The authors examined the contribution of working memory performance to subjective cognitive complaints in HIV infection beyond the influence of depressive symptoms. Thirty-six adults with HIV infection were administered neuropsychological (NP) tests of working memory, complex psychomotor efficiency, verbal learning, delayed recall, and questionnaires measuring depressive symptoms and cognitive complaints. Working memory performance, depression scores, and complex psychomotor efficiency were most strongly associated with self-reported cognitive complaints, whereas verbal learning scores and simple psychomotor efficiency showed more modest associations. Regression analyses revealed working memory performance to be the strongest NP predictor of self-reported cognitive complaints, comparable with depression scores in the amount of variance explained. These results suggest that working memory performance may be well suited to reflect how patients function in their everyday environment.

Executive control function in psychiatric and medical illness

Executive Control Function (ECF) is the ability to plan, sequence, and monitor one's behavior in order to accomplish a given goal while simultaneously exercising cognitive flexibility to adapt to changing task requirements. Multiple studies demonstrate that ECF predicts functional outcome, level of care required, and work potential for both well and ill populations. However, clinicians often do not routinely assess ECF during mental status evaluations because of the perceived lack of practical bedside tests. This review article discusses the major neuropsychological measures used to probe for impairment, with special emphasis on those that are easily administered at the patient's bedside. The current literature on executive dysfunction in psychiatric and medical illness is reviewed. The neuroanatomy and neurochemistry of ECF is also reviewed, with emphasis on structural dysfunction in specific illnesses. Finally, various treatment options, both pharmacological and psychotherapeutic, are discussed.

Methamphetamine and HIV-1: potential interactions and the use of the FIV/cat model

The interaction of methamphetamine with human immunodeficiency virus (HIV), the aetiologic agent of Acquired Immune Deficiency Syndrome (AIDS), has not been thoroughly investigated. However, increasingly, a larger proportion of HIV infected individuals acquire the virus through methamphetamine use or are exposed to this drug during their disease course. In certain populations, there is a convergence of methamphetamine use and HIV-1 infection; yet our understanding of the potential effects that simultaneous exposure to these two agents have on disease progression is extremely limited. Studying the interactions between methamphetamine and lentivirus in people is difficult. To thoroughly understand methamphetamine's effects on lentivirus disease progression, an animal model that is both clinically relevant and easily manipulated is essential. In this report, we identified potential problems with methamphetamine abuse in individuals with a concurrent HIV-1 infection, described the Feline Immunodeficiency Virus (FIV)/cat model for HIV-1, and reported our early findings using this modelling system to study the interaction of methamphetamine and lentivirus infections.

Preclinical psychopharmacology of AIDS-associated dementia: lessons to be learned from the cognitive psychopharmacology of other dementias

Following a brief discussion of the epidemiology, underlying neuropathological mechanisms, neuropsychological symptoms and present treatment strategies of AIDS-associated dementia (AAD), parallels are drawn between the longer standing research on drugs for the treatment of other cognitive disorders, particularly senile dementia, and ongoing efforts to develop psychopharmacological approaches for the treatment of the cognitive impairments in AAD. Important aspects of hypotheses designed to guide such a research are indicated with the help of a speculative, paradigmatic hypothesis concerning the role of cortical cholinergic inputs in AAD. Furthermore, aspects of validity of animal models, and cognition as a crucial intervening variable in the effects of potential treatments, are evaluated.

Performance norms for a rhesus monkey neuropsychological testing battery: acquisition and long-term performance

A computerized behavioral battery based upon human neuropsychological tests (CANTAB, CeNeS, Cambridge, UK) has been developed to assess cognitive behaviors of rhesus monkeys. Monkeys reliably performed multiple tasks, providing long-term assessment of changes in a number of behaviors for a given animal. The overall goal of the test battery is to characterize changes in cognitive behaviors following central nervous system (CNS) manipulations. The battery addresses memory (delayed non-matching to sample, DNMS; spatial working memory, using a self-ordered spatial search task, SOSS), attention (intra-/extra-dimensional shift, ID/ED), motivation (progressive-ratio, PR), reaction time (RT) and motor coordination (bimanual task). As with human neuropsychological batteries, different tasks are thought to involve different neural substrates, and therefore performance profiles should assess function in particular brain regions. Monkeys were tested in transport cages, and responding on a touch sensitive computer monitor was maintained by food reinforcement. Parametric manipulations of several tasks demonstrated the sensitivity of performance to increases in task difficulty. Furthermore, the factors influencing difficulty for rhesus monkeys were the same as those shown to affect human performance. Data from this study represent performance of a population of healthy normal monkeys that will be used for comparison in subsequent studies of performance following CNS manipulations such as infection with simian immunodeficiency virus (NeuroAIDS) or drug administration.

Glucocorticoids interact with gp120 in causing neurotoxicity in striatal cultures

A significant subset of HIV-positive patients suffer from AIDS-Related Dementia Complex (ADC), an array of neurologic and neuropsychologic impairments. The HIV coat protein gp120 has been implicated in the deleterious neurologic consequences of HIV infection, damaging neurons through a glutamatergic and calcium-dependent pathway. We have previously reported that glucocorticoids, the adrenal steroids secreted during stress, can exacerbate the neurotoxic and calcium-mobilizing effects of gp120 in hippocampal and cortical cultures. Because both the symptomatology of ADC, as well as the neuropathologic profile of post-mortem HIV brains suggests an involvement of the striatum, we examined whether glucocorticoids could also augment the damaging effects of gp120 in primary striatal cultures. We observe that neither gp120 nor the glucocorticoid corticosterone, when administered alone, cause neurotoxicity or mobilization of free cytosolic calcium; however, a combination of the two caused significant toxicity and neuron death. This, along with our prior findings of gp120-glucocorticoid interactions, is striking, given the heavy clinical use of synthetic glucocorticoids for management of pulmonary complications of HIV infection.

Longitudinal analysis of behavioral, neurophysiological, viral and immunological effects of SIV infection in rhesus monkeys

A model is proposed in which a neurovirulent, microglial-passaged, simian immunodeficiency virus (SIV) is used to produce central nervous system (CNS) pathology and behavioral deficits in rhesus monkeys reminiscent of those seen in humans infected with human immunodeficiency virus (HIV). The time course of disease progression was characterized by using functional measures of cognition and motor skill, as well as neurophysiologic monitoring. Concomitant assessment of immunological and virological parameters illustrated correspondence between impaired behavioral performance and viral pathogenesis. Convergent results were obtained from neuropathological findings indicative of significant CNS disease. In ongoing studies, this SIV model is being used to explore the behavioral sequelae of immunodeficiency virus infection, the viral and host factors leading to neurologic dysfunction, and to begin testing potential therapeutic agents.

Axonal sprouting in hippocampus of cats infected with feline immunodeficiency virus (FIV)

Neurologic dysfunction and neuropathology are common findings in patients infected with HIV and in cats infected with feline immunodeficiency virus (FIV). The pathogenesis of lentivirus-associated alterations in the central nervous system (CNS) is multifactorial. Because seizures, alterations in memory, and behavioral changes are clinical manifestations in adults and children infected with HIV, we explored the possibility that changes in neuronal structure may occur in the hippocampus. To do this, we examined the dentate gyrus of FIV-infected cats, an animal model of HIV infection. Neuropathologic findings included gliosis within the hilus of the dentate gyrus and granule cell axonal sprouting. Using the Timm's method, which labels axons of dentate gyrus granule cells, abnormally high amounts of staining were observed in the inner one third of the molecular layer in 45% of FIV-infected cats (n = 11) and in none of the controls (n = 19). Prominent axonal sprouting was seen in three FIV-infected cats that were infected as kittens, suggesting that younger cats may be more susceptible. Axon reorganization of the dentate granule cells has been hypothesized to underlie complex partial seizure activity in human temporal lobe epilepsy. These results suggest that FIV infection causes granule cell axon reorganization in the hippocampus of cats. A similar neuropathogenetic mechanism may contribute to neurologic dysfunction in HIV-infected patients.

Simian immunodeficiency virus: a model for neuroAIDS

In addition to its profound effects on the immune system, HIV also infects the CNS and can cause abnormalities in infected individuals ranging from mild cognitive and motor disorders to frank dementia. We have been actively investigating the molecular and cellular mechanisms underlying the CNS manifestations of lentivirus infection through the comparative evaluation of brain pathophysiology under a number of parallel interrelated strategies. Here we describe our ongoing studies with the SIV/rhesus macaque system. We have applied an interdisciplinary multistep approach, utilizing viral, immunological, pathological, behavioral, and electrophysiological techniques to assess disease and study CNS dysfunction induced by SIV. The profile of the infection and the host response, and the resulting cognitive, motor, and neurophysiological abnormalities in SIV-infected monkeys, recapitulates many aspects of the functional impairments associated with HIV-induced CNS disease in humans. Consequently, the SIV model is ideal for examining the mechanisms underlying these functional abnormalities and for testing potential therapeutic agents.

Microglia-passaged simian immunodeficiency virus induces neurophysiological abnormalities in monkeys

Four rhesus macaques were inoculated intravenously with a cryopreserved stock of microglia obtained from a simian immunodeficiency virus (SIV)-infected rhesus macaque. Before infection, three of the four monkeys were trained and tested daily on a computerized neuropsychological test battery. After SIV infection, behavioral testing continued to monitor deficits associated with disease progression. Five additional age-matched, behaviorally trained monkeys served as controls. Neurophysiological testing for visual and auditory evoked responses was accomplished 37-52 weeks after infection in all monkeys. Subsequently, all four SIV-infected monkeys and one control subject were sacrificed, and samples of brain tissue were taken for pathological analysis. SIV-infected monkeys demonstrated abnormal responses in both auditory and visual evoked responses. In addition, around the time of electrophysiological recording, all three SIV-infected, behaviorally trained monkeys exhibited significant decreases in progressive-ratio performance, reflecting a reduction in reinforcer efficacy. One subject also demonstrated impairments in shifting of attentional set and motor ability at that time. Neuropathological evaluation revealed that all four SIV-infected monkeys exhibited numerous perivascular and parenchymal infiltrating T cells. These findings document that SIV causes electrophysiological, behavioral, and neuropathological sequelae similar to what has been observed in the human neuroAIDS syndrome. Our observations further validate the simian model for the investigation of the pathogenesis of AIDS dementia and for the investigation of drugs with potential therapeutic benefits.

CANTAB battery: proposed utility in neurotoxicology

The CANTAB battery was developed for the assessment of cognitive deficits in humans with neurodegenerative diseases or brain damage. It consists of a series of interrelated computerized tests of memory, attention, and executive function, administered via a touch sensitive screen. It allows a decomposition of complex tasks commonly used in clinical assessment into their cognitive components and enables the extrapolation of findings from the animal literature. Tests include versions of the Wisconsin Card-Sorting Test and the Tower and London and also the Delayed Matching-to-Sample test, widely used in monkeys for visual recognition memory. The tests are constructed in such a way that they may be given to animals (monkeys) with minimal change. The nonverbal nature of the CANTAB tests makes them largely language independent and culture free. CANTAB has been standardized on a large, predominantly elderly, population and validated in neurosurgical patients as well as in patients with basal ganglia disorders, Alzheimer's disease, depression, and schizophrenia. In addition, CANTAB has been used to evaluate: a) the therapeutic effects of dopaminergic and cholinergic medication in neurodegenerative disease; b) cognition in 5-11-year-old normal, learning-disabled, and autistic children; c) deficits in patients with HIV infection; and d) early, asymptomatic Huntington's disease. The latter illustrate its usefulness in early identification of progressive disorders. It is suggested that the battery should have particular utility across a wide range of age and intelligence in longitudinal assessment after exposure to toxicants, and allow meaningful comparison with experimental studies of toxic effects in other species.