Cellular plasticity induced by anti-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor encephalitis antibodies

Objective

Autoimmune-mediated anti–α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) encephalitis is a severe but treatment-responsive disorder with prominent short-term memory loss and seizures. The mechanisms by which patient antibodies affect synapses and neurons leading to symptoms are poorly understood.

Methods

The effects of patient antibodies on cultures of live rat hippocampal neurons were determined with immunostaining, Western blot, and electrophysiological analyses.

Results

We show that patient antibodies cause a selective decrease in the total surface amount and synaptic localization of GluA1- and GluA2-containing AMPARs, regardless of receptor subunit binding specificity, through increased internalization and degradation of surface AMPAR clusters. In contrast, patient antibodies do not alter the density of excitatory synapses, N-methyl-D-aspartate receptor (NMDAR) clusters, or cell viability. Commercially available AMPAR antibodies directed against extracellular epitopes do not result in a loss of surface and synaptic receptor clusters, suggesting specific effects of patient antibodies. Whole-cell patch clamp recordings of spontaneous miniature postsynaptic currents show that patient antibodies decrease AMPAR-mediated currents, but not NMDAR-mediated currents. Interestingly, several functional properties of neurons are also altered: inhibitory synaptic currents and vesicular γ-aminobutyric acid transporter (vGAT) staining intensity decrease, whereas the intrinsic excitability of neurons and short-interval firing increase.

Interpretation

These results establish that antibodies from patients with anti-AMPAR encephalitis selectively eliminate surface and synaptic AMPARs, resulting in a homeostatic decrease in inhibitory synaptic transmission and increased intrinsic excitability, which may contribute to the memory deficits and epilepsy that are prominent in patients with this disorder.

Acute mechanisms underlying antibody effects in anti-N-methyl-D-aspartate receptor encephalitis

Objective

A severe but treatable form of immune-mediated encephalitis is associated with antibodies in serum and cerebrospinal fluid (CSF) against the GluN1 subunit of the N-methyl-D-aspartate receptor (NMDAR). Prolonged exposure of hippocampal neurons to antibodies from patients with anti-NMDAR encephalitis caused a reversible decrease in the synaptic localization and function of NMDARs. However, acute effects of the antibodies, fate of the internalized receptors, type of neurons affected, and whether neurons develop compensatory homeostatic mechanisms were unknown and are the focus of this study.

Methods

Dissociated hippocampal neuron cultures and rodent brain sections were used for immunocytochemical, physiological, and molecular studies.

Results

Patient antibodies bind to NMDARs throughout the rodent brain, and decrease NMDAR cluster density in both excitatory and inhibitory hippocampal neurons. They rapidly increase the internalization rate of surface NMDAR clusters, independent of receptor activity. This internalization likely accounts for the observed decrease in NMDAR-mediated currents, as no evidence of direct blockade was detected. Once internalized, antibody-bound NMDARs traffic through both recycling endosomes and lysosomes, similar to pharmacologically induced NMDAR endocytosis. The antibodies are responsible for receptor internalization, as their depletion from CSF abrogates these effects in hippocampal neurons. We find that although anti-NMDAR antibodies do not induce compensatory changes in glutamate receptor gene expression, they cause a decrease in inhibitory synapse density onto excitatory hippocampal neurons.

Interpretation

Our data support an antibody-mediated mechanism of disease pathogenesis driven by immunoglobulin-induced receptor internalization. Antibody-mediated downregulation of surface NMDARs engages homeostatic synaptic plasticity mechanisms, which may inadvertently contribute to disease progression. Ann Neurol 2014;76:108–119

Refractoriness enhances temporal coding by auditory nerve fibers

A universal property of spiking neurons is refractoriness, a transient decrease in discharge probability immediately following an action potential (spike). The refractory period lasts only one to a few milliseconds, but has the potential to affect temporal coding of acoustic stimuli by auditory neurons, which are capable of submillisecond spike-time precision. Here this possibility was investigated systematically by recording spike times from chicken auditory nerve fibers in vivo while stimulating with repeated pure tones at characteristic frequency. Refractory periods were tightly distributed, with a mean of 1.58 ms. A statistical model was developed to recapitulate each fiber's responses and then used to predict the effect of removing the refractory period on a cell-by-cell basis for two largely independent facets of temporal coding: faithful entrainment of interspike intervals to the stimulus frequency and precise synchronization of spike times to the stimulus phase. The ratio of the refractory period to the stimulus period predicted the impact of refractoriness on entrainment and synchronization. For ratios less than ∼0.9, refractoriness enhanced entrainment and this enhancement was often accompanied by an increase in spike-time precision. At higher ratios, little or no change in entrainment or synchronization was observed. Given the tight distribution of refractory periods, the ability of refractoriness to improve temporal coding is restricted to neurons responding to low-frequency stimuli. Enhanced encoding of low frequencies likely affects sound localization and pitch perception in the auditory system, as well as perception in nonauditory sensory modalities, because all spiking neurons exhibit refractoriness.

Collaborative filtering for brain-computer interaction using transfer learning and active class selection

Brain-computer interaction (BCI) and physiological computing are terms that refer to using processed neural or physiological signals to influence human interaction with computers, environment, and each other. A major challenge in developing these systems arises from the large individual differences typically seen in the neural/physiological responses. As a result, many researchers use individually-trained recognition algorithms to process this data. In order to minimize time, cost, and barriers to use, there is a need to minimize the amount of individual training data required, or equivalently, to increase the recognition accuracy without increasing the number of user-specific training samples. One promising method for achieving this is collaborative filtering, which combines training data from the individual subject with additional training data from other, similar subjects. This paper describes a successful application of a collaborative filtering approach intended for a BCI system. This approach is based on transfer learning (TL), active class selection (ACS), and a mean squared difference user-similarity heuristic. The resulting BCI system uses neural and physiological signals for automatic task difficulty recognition. TL improves the learning performance by combining a small number of user-specific training samples with a large number of auxiliary training samples from other similar subjects. ACS optimally selects the classes to generate user-specific training samples. Experimental results on 18 subjects, using both nearest neighbors and support vector machine classifiers, demonstrate that the proposed approach can significantly reduce the number of user-specific training data samples. This collaborative filtering approach will also be generalizable to handling individual differences in many other applications that involve human neural or physiological data, such as affective computing.

Validity of the Virtual Reality Stroop Task (VRST) in active duty military

Virtual environments provide the ability to systematically deliver test stimuli in simulated contexts relevant to real world behavior. The current study evaluated the validity of the Virtual Reality Stroop Task (VRST), which presents test stimuli during a virtual reality military convoy with simulated combat threats. Active duty Army personnel (N = 49) took the VRST, a customized version of the Automated Neuropsychological Assessment Metrics (ANAM)-Fourth Edition TBI Battery (2007) that included the addition of the ANAM Stroop and Tower tests, and traditional neuropsychological measures, including the Delis-Kaplan Executive Function System version of the Color-Word Interference Test. Preliminary convergent and discriminant validity was established, and performance on the VRST was significantly associated with computerized and traditional tests of attention and executive functioning. Valid virtual reality cognitive assessments open new lines of inquiry into the impact of environmental stimuli on performance and offer promise for the future of neuropsychological assessments used with military personnel.

Determinants of synaptic strength vary across an axon arbor

We used synaptophysin-pHluorin expressed in hippocampal neurons to address how functional properties of terminals, namely, evoked release, total vesicle pool size, and release fraction, vary spatially across individual axon arbors. Consistent with previous reports, over short arbor distances (≈ 100 μm), evoked release was spatially heterogeneous when terminals contacted different postsynaptic dendrites or neurons. Regardless of the postsynaptic configuration, the evoked release and total vesicle pool size spatially covaried, suggesting that the fraction of synaptic vesicles available for release (release fraction) was similar over short distances. Evoked release and total vesicle pool size were highly correlated with the amount of NMDA receptors and PSD-95 in postsynaptic specialization. However, when individual axons were followed over longer distances (several hundred micrometers), a significant increase in evoked release was observed distally that was associated with an increased release fraction in distal terminals. The increase in distal release fraction can be accounted for by changes in individual vesicle release probability as well as readily releasable pool size. Our results suggest that for a single axon arbor, presynaptic strength indicated by evoked release over short distances is correlated with heterogeneity in total vesicle pool size, whereas over longer distances presynaptic strength is correlated with the spatial modulation of release fraction. Thus the mechanisms that determine synaptic strength differ depending on spatial scale.

Virtual reality paced serial assessment test for neuropsychological assessment of a military cohort

The assessment and treatment of traumatic brain injury (TBI) has become a difficult challenge for the DoD medical health system. Clinical neuropsychologists are being asked to make statements regarding a soldier's functional skills, ability to return to active duty, and competence in tasks of community living. Given the increasing prevalence of blast injuries to the head, and the fact that many brain injuries may have no external marker of injury, there is need for researching innovative assessment methods in detecting blast-related brain injury. To address these issues, two virtual reality-based Paced Auditory/Visual Serial Addition Tests (PA/VSAT) were developed that involve the participant being immersed in a Virtual Middle Eastern City as serial addition stimuli are presented. This study is an initial validation of the VRPASAT and VRPVSAT as assessments of neurocognitive functioning. When compared to the paper-and-pencil version of the test, as well as the Automated Neuropsychological Assessment Metrics, the VRPASAT and VRPVSAT appear to have enhanced capacity for providing an indication of a participant's performance while immersed in a military relevant simulation.

Virtual Simulations and the Second Life Metaverse

In neuropsychology’s received paradigm, the “normal science” of assessment and treatment planning appears to be approaching a paradigm shift: first, there are the general developments in other neurosciences that inform the practice of neuropsychological assessment. Second, there is the shift in the purpose of neuropsychological assessment from differential diagnosis of brain pathology to predictions about activities of everyday functioning and treatment planning. Third, there is growing need that neuropsychologists update their outdated technology for ecologically valid assessments. The impending paradigm shift may be well served to include the utility of virtual worlds for ecologically valid neuropsychological assessments. Actualization of the potential of virtual worlds for assessment will require the following: comparisons with well-validated neuropsychological measures, data storage, improved documentation of specific computer hardware and software used in experimental methods, and enhanced methods and result reporting by the researchers publishing studies on virtual worlds.

Virtual Reality Stroop Task for neurocognitive assessment

Given the prevalence of traumatic brain injury (TBI), and the fact that many mild TBIs have no external marker of injury, there is a pressing need for innovative assessment technology. The demand for assessment that goes beyond traditional paper-and-pencil testing has resulted in the use of automated cognitive testing for increased precision and efficiency; and the use of virtual environment technology for enhanced ecological validity and increased function-based assessment. To address these issues, a Virtual Reality Stroop Task (VRST) that involves the subject being immersed in a virtual Humvee as Stroop stimuli appear on the windshield was developed. This study is an initial validation of the VRST as an assessment of neurocognitive functioning. When compared to the paper-and-pencil, as well as Automated Neuropsychological Assessment Metrics versions of the Stroop, the VRST appears to have enhanced capacity for providing an indication of a participant's reaction time and ability to inhibit a prepotent response while immersed in a military relevant simulation that presents psychophysiologically arousing high and low threat stimuli.

Neurocognitive and Psychophysiological Interfaces for Adaptive Virtual Environments

The use of neuropsychological and psychophysiological measures in studies of patients immersed in high-fidelity virtual environments offers the potential to develop current psychophysiological computing approaches into affective computing scenarios that can be used for assessment, diagnosis and treatment planning. Such scenarios offer the potential for simulated environments to proffer cogent and calculated response approaches to real-time changes in user emotion, neurocognition, and motivation. The value in using virtual environments to produce simulations targeting these areas has been acknowledged by an encouraging body of research. Herein the authors describe (1) literature on virtual environments for neurocognitive and psychophysiological profiles of users’ individual strengths and weaknesses; and (2) real-time adaptation of virtual environments that could be used for virtual reality exposure therapy and cognitive rehabilitation. Specifically, the authors discuss their approach to an adaptive environment that uses the principles of flow, presence, neuropsychology, psychophysiology to develop a novel application for rehabilitative applications.

Backpropagation and Regression: Comparative Utility for Neuropsychologists

The aim of this research was to compare the data analytic applicability of a backpropagated neural network with that of regression analysis. Thirty individuals between the ages of 64 and 86 (Mean age = 73.6; Mean years education = 15.4; % women = 50) participated in a study designed to validate a new test of spatial ability administered in virtual reality. As part of this project a standard neuropsychological battery was administered. Results from the multiple regression model R(2) = .21, p < .28; Standard Error = 18.01) were compared with those of a backpropagated ANN (R(2) = .39, p < .02; Standard Error = 13.07). This 18% increase in prediction of a common neuropsychological problem demonstrated that an ANN has the potential to outperform a regression.

Better than the real thing: eliciting fear with moving and static computer-generated stimuli

As the popularity of virtual reality as an exposure therapy increases, it is important to validate the use of computer-generated stimuli in comparison to standardized images of "real" phobic objects, such as those of the International Affective Picture System (IAPS). The present study examined physiological and subjective measures of negative affect when viewing static IAPS images, static computer-generated images and moving videos of computer-generated images of feared stimuli and other negative stimuli which were not specifically feared. For example, a picture of a spider would be a "feared" stimulus for a spider fearful participant, whereas a picture of a snake would be categorized as a "negative" stimulus for that participant. Eighteen participants scoring high (high fear (HF) cohort) on questionnaires assessing specific fears of spiders or snakes and 20 participants scoring low (low fear (LF) cohort) on the questionnaires viewed the stimuli. The computer-generated videos elicited greater physiological (skin conductance and startle eyeblink potentiation) and self-report arousal responses than the IAPS images and the computer-generated static images. Computer-generated stills and IAPS images did not differ in eliciting emotional responses. Additionally, HF participants showed greater heart rate acceleration and larger skin conductance responses to their feared stimulus than to the negative stimulus, especially when viewing computer-generated moving videos. The results demonstrate the importance of motion in eliciting fear and the usefulness of computer-generated stimuli in the study of emotion.

Virtual reality in paediatric rehabilitation: a review

OBJECTIVE

To provide a narrative review of studies regarding the outcomes of Virtual Reality (VR)-based treatment and rehabilitation programmes within the paediatric population.

METHODS

Studies related to the use of VR across a number of paediatric areas (e.g. cerebral palsy, autism, foetal alcohol syndrome and attention deficits) were identified and summarized.

RESULTS

Outcomes from the studies reviewed provide preliminary support for the use of VR.

CONCLUSION

VR may be an effective treatment method for specific disorders, although the generalizability of this literature is hindered by several methodological limitations, such as small samples and the absence of appropriate control participants.

MEMORY IMPROVEMENT WITH TREATMENT OF HYPOTHYROIDISM

The consequences of inadequate thyroid hormone availability to the brain and treatment effects of levothyroxine on cognitive function are still poorly understood. This study prospectively assessed the effects of thyroid replacement therapy on cognitive function in patients suffering from biochemical evidenced, untreated hypothyroidism. Significant effects between the untreated hypothyroid group and control group were limited to verbal memory retrieval. When assessing the effects of 3-month treatment, results revealed that the treated hypothyroid group had significant increased verbal memory retrieval. Results suggest that specific memory retrieval deficits associated with hypothyroidism can resolve after replacement therapy with levothyroxine.

PREGNANCY HISTORY AND COGNITION DURING AND AFTER PREGNANCY

An increasing body of literature confirms anecdotal reports that cognitive changes occur during pregnancy. This article assessed whether prior pregnancy, which alters a woman's subsequent hormonal environment, is associated with a specific cognitive profile during and after pregnancy. Seven primigravids and nine multigravids were compared, equivalent for age and education. No differences between groups were found during pregnancy. After delivery, multigravids performed better than primigravids on verbal memory tasks. After controlling for mood, a significant difference in verbal memory remained. A neuroadaptive mechanism may develop after first pregnancy that increases the ability to recover from some cognitive deficits after later pregnancies.

Application of reliable change indices to computerized neuropsychological measures of concussion

Serial assessments of neurocognitive functioning in athletes with concussion are commonly used for return to play decisions. This study provides reliable change indices (RCIs) for computerized tests from 40 NCAA Division I collegiate athletes that suffered a sports-related concussion. The normative data that resulted from the RCIs and subsequent analyses of differences between improved and not improved athletes may aid both clinicians and researchers to assess whether observed change on neuropsychological measures is reliable change or change due simply to practice effects. Hence, the RCIs presented herein provide information that may be used judiciously by a clinician for assessing meaningful change.

A virtual human agent for assessing bias in novice therapists

Monitoring the psychological and physiological activity of persons interacting with virtual humans poses exacting measurement challenges. Three experiments are reported in this paper. In these experiments we made use of Virtual Human Agent technology to assess persons' psychological and physiological responses to Virtual Standardized Patients. The first experiment provided support for the usability of the Virtual Standardized Patients through the use of a virtual character emulating an adolescent male with conduct disorder. In the second experiment we further developed the technology and aimed at assessing whether novice mental health clinicians could conduct an interview with a virtual character that emulates an adolescent female who has recently been physically traumatized. The third experiment looked at the usability of Virtual Standardized Patients for eliciting psychophysiological responses following exposure to virtual humans representing different ethnicities.

Optimizing Clinical Training for the Treatment of PTSD Using Virtual Patients

Adequate treatment of PTSD is a growing concern for the military. However, there is a shortage of qualified personnel available to apply this treatment. Virtual patient systems offer a novel technology to enhance the training needs of such health providers. This pilot project builds on previous work done with virtual patients and describes a novel scenario wherein a virtual patient is immersed within an exposure therapy simulation while a clinician interacts and guides the virtual patient through the recovery process using exposure therapy for PTSD. While this work is ongoing, preliminary results will be presented.

Neurocognitive and psychophysiological analysis of human performance within virtual reality environments

Monitoring the neurocognitive and psychophysiological activity of persons operating within a complex environment poses exacting measurement challenges. Three experiments are reported in this paper. In these experiments we made use of VRCPAT to assess persons' neurocognitive and psychophysiological responses to high-fidelity, immersive virtual environments. The first experiment provided continued support for the validity of the VRCPAT as a measure of learning and memory through the use of an increased sample size. In the second experiment we aimed at assessing whether an increase in stimulus complexity would result in a significant decrease in performance on attentional tasks. We also wanted to see whether an increase in stimulus intensity would result in a significant decrease in performance on attentional tasks. The third experiment looked at participants' psychophysiological responses in both low and high immersion virtual environments.

A Comparative Analysis between Experts and Novices Interacting with a Virtual Patient with PTSD

Virtual patients will provide a means to train the next generation of clinical residents. Interacting and engaging with virtual characters portraying standardized patients can have meaningful outcomes. As a cumulative set of data analysis, we investigate the comparison of how well novices, subjects without any clinical interviewing background, with experts, clinicians, or resident student clinicians with interviewing skills to assess if they could elicit the proper information from verbal interactions with a virtual character.

Affective outcomes of virtual reality exposure therapy for anxiety and specific phobias: a meta-analysis

Virtual reality exposure therapy (VRET) is an increasingly common treatment for anxiety and specific phobias. Lacking is a quantitative meta-analysis that enhances understanding of the variability and clinical significance of anxiety reduction outcomes after VRET. Searches of electronic databases yielded 52 studies, and of these, 21 studies (300 subjects) met inclusion criteria. Although meta-analysis revealed large declines in anxiety symptoms following VRET, moderator analyses were limited due to inconsistent reporting in the VRET literature. This highlights the need for future research studies that report uniform and detailed information regarding presence, immersion, anxiety and/or phobia duration, and demographics.

Synaptic ribbon enables temporal precision of hair cell afferent synapse by increasing the number of readily releasable vesicles: a modeling study

Synaptic ribbons are classically associated with mediating indefatigable neurotransmitter release by sensory neurons that encode persistent stimuli. Yet when hair cells lack anchored ribbons, the temporal precision of vesicle fusion and auditory nerve discharges are degraded. A rarified statistical model predicted increasing precision of first-exocytosis latency with the number of readily releasable vesicles. We developed an experimentally constrained biophysical model to test the hypothesis that ribbons enable temporally precise exocytosis by increasing the readily releasable pool size. Simulations of calcium influx, buffered calcium diffusion, and synaptic vesicle exocytosis were stochastic (Monte Carlo) and yielded spatiotemporal distributions of vesicle fusion consistent with experimental measurements of exocytosis magnitude and first-spike latency of nerve fibers. No single vesicle could drive the auditory nerve with requisite precision, indicating a requirement for multiple readily releasable vesicles. However, plasmalemma-docked vesicles alone did not account for the nerve's precision--the synaptic ribbon was required to retain a pool of readily releasable vesicles sufficiently large to statistically ensure first-exocytosis latency was both short and reproducible. The model predicted that at least 16 readily releasable vesicles were necessary to match the nerve's precision and provided insight into interspecies differences in synaptic anatomy and physiology. We confirmed that ribbon-associated vesicles were required in disparate calcium buffer conditions, irrespective of the number of vesicles required to trigger an action potential. We conclude that one of the simplest functions ascribable to the ribbon--the ability to hold docked vesicles at an active zone--accounts for the synapse's temporal precision.

Objective structured clinical interview training using a virtual human patient

Effective interview skills are a core competency for psychiatry residents and developing psychotherapists. Although schools commonly make use of standardized patients to teach interview skills, the diversity of the scenarios standardized patients can characterize is limited by availability of human actors. Further, there is the economic concern related to the time and money needed to train standardized patients. Perhaps most damaging is the "standardization" of standardized patients -- will they in fact consistently proffer psychometrically reliable and valid interactions with the training clinicians. Virtual Human Agent (VHA) technology has evolved to a point where researchers may begin developing mental health applications that make use of virtual reality patients. The work presented here is a preliminary attempt at what we believe to be a large application area. Herein we describe an ongoing study of our virtual patients (VP). We present an approach that allows novice mental health clinicians to conduct an interview with a virtual character that emulates an adolescent male with conduct disorder. This study illustrates the ways in which a variety of core research components developed at the University of Southern California facilitates the rapid development of mental health applications.

Virtual environment for assessment of neurocognitive functioning: virtual reality cognitive performance assessment test

While standard neuropsychological measures have been found to have adequate predictive value, their ecological validity may diminish predictions about real world functioning. Virtual environments (VEs) are increasingly recognized as ecologically valid tools for neuropsychological assessment. We aim to develop a VE-based neuropsychological battery delivered within the context of a virtual city: Virtual Reality Cognitive Performance Assessment Test (VRCPAT). The 15 minute VRCPAT battery and 1.5 hour in-person neuropsychological assessment were conducted with a sample of 40 healthy adults, between the ages of 21 and 36, that included equivalent distributions of men and women from ethnically diverse populations. No subjects had history of psychiatric or neurologic conditions. Results supported both convergent and discriminant validity. The VRCPAT was found to correlate significantly with traditional neuropsychological tests assessing similar target constructs. No significant correlations existed between VRCPAT measures and non-target constructs. Findings suggest that the VRCPAT measures a capacity consistent with that of traditional neurocognitive measures; and is inconsistent with potential confounds. We conclude that the VRCPAT provides a unique opportunity to reliably and efficiently study neurocognitive function within an ecologically valid environment.

Cognitive effects of short-term use of raloxifene: a randomized clinical trial

Two questions regarding findings from the Women's Health Initiative are (1) What is the effect of various hormonal regimens including selective estrogen receptor modulators? and (2) Is the negative effect on cognitive functioning related to the older age (65+ years) of the women? This study addresses these two questions in a short-term randomized trial of the effects of raloxifene versus alendronate on cognition. The study found only one significant interaction where the raloxifene and alendronate group changed differently across the two testing occasions. Hence, raloxifene does not have any impact, positive or negative, on short-term cognitive functioning when compared to alendronate.

A controlled clinical comparison of attention performance in children with ADHD in a virtual reality classroom compared to standard neuropsychological methods

In this initial pilot study, a controlled clinical comparison was made of attention perforance in children with attention deficit-hyperactivity disorder (ADHD) in a virtual reality (VR) classroom. Ten boys diagnosed with ADHD and ten normal control boys participated in the study. Groups did not significantly differ in mean age, grade level, ethnicity, or handedness. No participants reported simulator sickness following VR exposure. Children with ADHD exhibited more omission errors, commission errors, and overall body movement than normal control children in the VR classroom. Children with ADHD were more impacted by distraction in the VR classroom. VR classroom measures were correlated with traditional ADHD assessment tools and the flatscreen CPT. Of note, the small sample size incorporated in each group and higher WISC-III scores of normal controls might have some bearing on the overall interpretation of results. These data suggested that the Virtual Classroom had good potential for controlled performance assessment within an ecologically valid environment and appeared to parse out significant effects due to the presence of distraction stimuli.

Immersiveness and physiological arousal within panoramic video-based virtual reality

In this paper, we discuss findings from a study that used panoramic video-based virtual environments (PVVEs) to induce self-reported anger. The study assessed "immersiveness" and physiological correlates of anger arousal (i.e., heart rate, blood pressure, galvanic skin response [GSR], respiration, and skin temperature). Results indicate that over time, panoramic video-based virtual scenarios can be, at the very least, physiologically arousing. Further, it can be affirmed from the results that hypnotizability, as defined by the applied measures, interacts with group on physiological arousal measures. Hence, physiological arousal appeared to be moderated by participant hypnotizability and absorption levels.

The prevalence and incidence of neurocognitive impairment in the HAART era

OBJECTIVES

HAART suppresses HIV viral replication and restores immune function. The effects of HAART on neurological disease are less well understood. The aim of this study was to assess the prevalence and incidence of neurocognitive impairment in individuals who initiated HAART as part of an AIDS clinical trial.

DESIGN

A prospective cohort study of HIV-positive patients enrolled in randomized antiretroviral trials, the AIDS Clinical Trials Group (ACTG) Longitudinal Linked Randomized Trials (ALLRT) study.

METHODS

We examined the association between baseline and demographic characteristics and neurocognitive impairment among 1160 subjects enrolled in the ALLRT study.

RESULTS

A history of immunosuppression (nadir CD4 cell count < 200 cells/microl) was associated with an increase in prevalent neurocognitive impairment. There were no significant virological and immunological predictors of incident neurocognitive impairment. Current immune status (low CD4 cell count) was associated with sustained prevalent impairment.

CONCLUSION

The association of previous advanced immunosuppression with prevalent and sustained impairment suggests that there is a non-reversible component of neural injury that tracks with a history of disease progression. The association of sustained impairment with worse current immune status (low CD4 cell count) suggests that restoring immunocompetence increases the likelihood of neurocognitive recovery. Finally, the lack of association between incident neurocognitive impairment and virological and immunological indicators implies that neural injury continues in some patients regardless of the success of antiretroviral therapy on these laboratory measures.

The prevalence and incidence of neurocognitive impairment in the HAART era

OBJECTIVES

HAART suppresses HIV viral replication and restores immune function. The effects of HAART on neurological disease are less well understood. The aim of this study was to assess the prevalence and incidence of neurocognitive impairment in individuals who initiated HAART as part of an AIDS clinical trial.

DESIGN

A prospective cohort study of HIV-positive patients enrolled in randomized antiretroviral trials, the AIDS Clinical Trials Group (ACTG) Longitudinal Linked Randomized Trials (ALLRT) study.

METHODS

We examined the association between baseline and demographic characteristics and neurocognitive impairment among 1160 subjects enrolled in the ALLRT study.

RESULTS

A history of immunosuppression (nadir CD4 cell count < 200 cells/microl) was associated with an increase in prevalent neurocognitive impairment. There were no significant virological and immunological predictors of incident neurocognitive impairment. Current immune status (low CD4 cell count) was associated with sustained prevalent impairment.

CONCLUSION

The association of previous advanced immunosuppression with prevalent and sustained impairment suggests that there is a non-reversible component of neural injury that tracks with a history of disease progression. The association of sustained impairment with worse current immune status (low CD4 cell count) suggests that restoring immunocompetence increases the likelihood of neurocognitive recovery. Finally, the lack of association between incident neurocognitive impairment and virological and immunological indicators implies that neural injury continues in some patients regardless of the success of antiretroviral therapy on these laboratory measures.

Adaptation reduces spike-count reliability, but not spike-timing precision, of auditory nerve responses

Sensory systems use adaptive coding mechanisms to filter redundant information from the environment to efficiently represent the external world. One such mechanism found in most sensory neurons is rate adaptation, defined as a reduction in firing rate in response to a constant stimulus. In auditory nerve, this form of adaptation is likely mediated by exhaustion of release-ready synaptic vesicles in the cochlear hair cell. To better understand how specific synaptic mechanisms limit neural coding strategies, we examined the trial-to-trial variability of auditory nerve responses during short-term rate-adaptation by measuring spike-timing precision and spike-count reliability. After adaptation, precision remained unchanged, whereas for all but the lowest-frequency fibers, reliability decreased. Modeling statistical properties of the hair cell-afferent fiber synapse suggested that the ability of one or a few vesicles to elicit an action potential reduces the inherent response variability expected from quantal neurotransmitter release, and thereby confers the observed count reliability at sound onset. However, with adaptation, depletion of the readily releasable pool of vesicles diminishes quantal content and antagonizes the postsynaptic enhancement of reliability. These findings imply that during the course of short-term adaptation, coding strategies that employ a rate code are constrained by increased neural noise because of vesicle depletion, whereas those that employ a temporal code are not.

Verbal memory retrieval deficits associated with untreated hypothyroidism

The effects of inadequate thyroid hormone availability to the brain on adult cognitive function are poorly understood. This study assessed the effects of hypothyroidism on cognitive function using a standard neuropsychological battery in 14 patients suffering from untreated hypothyroidism and complaining of subjective cognitive difficulties in comparison with 10 age-matched healthy comparison subjects. Significant differences between groups were limited to verbal memory retrieval as measured by the California Verbal Learning Test (CVLT). On short delay free recall, long delay free recall, and long delay cued recall, significant differences remained between groups despite the limited statistical power of this study. There were no significant results found between groups on attentional or nonverbal tasks. Results suggest that hypothyroid-related memory deficits are not attributable to an attentional deficit but rather to specific retrieval deficits.

Validation of the Cognitive Assessment of Later Life Status (CALLS) instrument: a computerized telephonic measure

BACKGROUND

Brief screening tests have been developed to measure cognitive performance and dementia, yet they measure limited cognitive domains and often lack construct validity. Neuropsychological assessments, while comprehensive, are too costly and time-consuming for epidemiological studies. This study's aim was to develop a psychometrically valid telephone administered test of cognitive function in aging.

METHODS

Using a sequential hierarchical strategy, each stage of test development did not proceed until specified criteria were met. The 30 minute Cognitive Assessment of Later Life Status (CALLS) measure and a 2.5 hour in-person neuropsychological assessment were conducted with a randomly selected sample of 211 participants 65 years and older that included equivalent distributions of men and women from ethnically diverse populations.

RESULTS

Overall Cronbach's coefficient alpha for the CALLS test was 0.81. A principal component analysis of the CALLS tests yielded five components. The CALLS total score was significantly correlated with four neuropsychological assessment components. Older age and having a high school education or less was significantly correlated with lower CALLS total scores. Females scored better overall than males. There were no score differences based on race.

CONCLUSION

The CALLS test is a valid measure that provides a unique opportunity to reliably and efficiently study cognitive function in large populations.

Pattern of neuropsychological performance among HIV positive patients in Uganda

Background

Few studies have examined cognitive functioning of HIV positive patients in sub-Saharan Africa. It cannot be assumed that HIV positive patients in Africa exhibit the same declines as patients in high-resource settings, since there are differences that may influence cognitive functioning including nutrition, history of concomitant disease, and varying HIV strains, among other possibilities. Part of the difficulty of specifying abnormalities in neuropsychological functioning among African HIV positive patients is that there are no readily available African normative databases. The purpose of the current study was to evaluate the pattern of neuropsychological performance in a sample of HIV positive patients in comparison to HIV negative control subjects in Uganda.

Methods

The neuropsychological test scores of 110 HIV positive patients (WHO Stage 2, n = 21; WHO Stage 3, n = 69; WHO Stage 4, n = 20) were contrasted with those of 100 control subjects on measures of attention/concentration, mental flexibility, learning/memory, and motor functioning.

Results

Analysis of covariance (ANCOVA) revealed significant group differences on measures of verbal learning and memory, speed of processing, attention and executive functioning between HIV seropositive and seronegative subjects.

Conclusion

Ugandan patients with HIV demonstrated relative deficits on measures of verbal learning and memory, speed of processing, attention, and executive functioning compared to HIV negative controls. These results from a resource limited region where clades A and D are prevalent are consistent with previous findings in the developed world where clade B predominates.

Motor based assessment of neurocognitive functioning in resource-limited international settings

This study compared variance accounted for by neuropsychological tests in both a brief motor battery and in a comprehensive neuropsychological battery. 327 HIV+ subjects received a comprehensive cognitive battery and a shorter battery (Timed Gait, Grooved Pegboard, and Fingertapping). A significant correlation existed between the motor component tests and the more comprehensive battery (52% of variance). Adding Digit symbol and Trailmaking increased the amount of variance accounted for (73%). Motor battery sensitivity to impairment diagnosis was 0.79 and specificity was 0.76. A motor battery may have broader utility to diagnose and monitor HIV related neurocognitive disorders in international settings.

The MMPI-2 Fake Bad Scale: Concordance and Specificity of True and Estimated Scores

A number of recent studies have supported the use of the MMPI-2 Fake Bad Scale (FBS) as a measure of negative response bias, the scale at times demonstrating greater sensitivity to negative response bias than other MMPI-2 validity scales. However, clinicians may not always have access to True FBS (T-FBS) scores, such as when True-False answer sheets are unavailable or published research studies do not report FBS raw scores. Under these conditions, Larrabee (2003a) suggests a linear regression formula that provides estimated FBS (E-FBS) scores derived from weighted validity and clinical T-Scores. The present study intended to validate this regression formula of MMPI-2 E-FBS scores and demonstrate its specificity in a sample of non-litigating, clinically referred, medically intractable epilepsy patients. We predicted that the E-FBS scores would correlate highly (>.70) with the T-FBS scores, that the E-FBS would show comparable correlations with MMPI-2 validity and clinical scales relative to the T-FBS, and that the E-FBS would show an adequate ability to match T-FBS scores using a variety of previously suggested T-FBS raw score cutoffs. Overall, E-FBS scores correlated very highly with T-FBS scores (r = .78, p < .0001), though correlations were especially high for women (r = .85, p < .0001) compared to men (r = .62, p < .001). Thirty-one of 32 (96.9%) comparisons made between E-FBS/T-FBS correlates with other MMPI-2 scales were nonsignificant. When matching to T-FBS "high" and "low" scores, the E-FBS scores demonstrated the highest hit rate (92.5%) through use of Lees-Haley's (1992) revised cutoffs for men and women. These same cutoffs resulted in excellent overall specificity for both the T-FBS scores (92.5%) and E-FBS scores (90.6%). The authors conclude that the E-FBS represents an adequate estimate of T-FBS scores in the current epilepsy sample. Use of E-FBS scores may be especially useful when clinicians conduct the MMPI-2 short form, which does not include all of the 43 FBS items but does include enough items to compute each of the validity and clinical T-Scores. Future studies should examine E-FBS sensitivity in compensation-seekers with incomplete effort.

Assessing health-related quality of life in NeuroAIDS: some psychometric properties of the Neurological Quality of Life Questionnaire (NeuroQOL)

Several studies were undertaken to assess the psychometric properties (reliability and initial convergent and discriminant construct validity) of the Neurological Quality of Life Questionnaire (NeuroQOL). The NeuroQOL contains 114 items answered in self report Likert format, with higher scores reflecting better quality of life. Study one compared the questionnaire with existing quality of life measures (Symptom Distress Scale, Sickness Impact Profile) and a significant (p<0.05) correlation was found. Studies two through five evaluated the relationship between the NeuroQOL and disease stage, psychological, neuropsychological and neurological measures, and a significant correlation was also found with each domain. The internal consistency reliability (alpha=0.96), split half reliability (r(12)=0.97), and test-retest reliability (coefficients were 0.78 for 6 months and 0.67 for one year intervals between test and retest) were all found to be high and adequately stable. Overall, these results indicate acceptable reliability and initial construct validity for the NeuroQOL.

Neurocognitive differential diagnosis of dementing diseases: Alzheimer's Dementia, Vascular Dementia, Frontotemporal Dementia, and Major Depressive Disorder

Similarities in presentation of Dementia of Alzheimer's Type, Vascular Dementia, Frontotemporal Dementia, and Major Depressive Disorder, pose differential diagnosis challenges. The current study identifies specific neuropsychological patterns of scores for Dementia of Alzheimer's Type, Vascular Dementia, Frontotemporal Dementia, and Major Depressive Disorder. Neuropsychological domains directly assessed in the study included: immediate memory, delayed memory, confrontational naming, verbal fluency, attention, concentration, and executive functioning. The results reveal specific neuropsychological comparative profiles for Dementia of Alzheimer's Type, Vascular Dementia, Frontotemporal Dementia, and Major Depressive Disorder. The identification of these profiles will assist in the differential diagnosis of these disorders and aid in patient treatment.

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.