Earthquake and tsunami forecasts: relation of slow slip events to subsequent earthquake rupture.

The 5 September 2012 M(w) 7.6 earthquake on the Costa Rica subduction plate boundary followed a 62-y interseismic period. High-precision GPS recorded numerous slow slip events (SSEs) in the decade leading up to the earthquake, both up-dip and down-dip of seismic rupture. Deeper SSEs were larger than shallower ones and, if characteristic of the interseismic period, release most locking down-dip of the earthquake, limiting down-dip rupture and earthquake magnitude. Shallower SSEs were smaller, accounting for some but not all interseismic locking. One SSE occurred several months before the earthquake, but changes in Mohr-Coulomb failure stress were probably too small to trigger the earthquake. Because many SSEs have occurred without subsequent rupture, their individual predictive value is limited, but taken together they released a significant amount of accumulated interseismic strain before the earthquake, effectively defining the area of subsequent seismic rupture (rupture did not occur where slow slip was common). Because earthquake magnitude depends on rupture area, this has important implications for earthquake hazard assessment. Specifically, if this behavior is representative of future earthquake cycles and other subduction zones, it implies that monitoring SSEs, including shallow up-dip events that lie offshore, could lead to accurate forecasts of earthquake magnitude and tsunami potential.

Plate-boundary deformation associated with the great Sumatra-Andaman earthquake.

The Sumatra-Andaman earthquake of 26 December 2004 is the first giant earthquake (moment magnitude M(w) > 9.0) to have occurred since the advent of modern space-based geodesy and broadband seismology. It therefore provides an unprecedented opportunity to investigate the characteristics of one of these enormous and rare events. Here we report estimates of the ground displacement associated with this event, using near-field Global Positioning System (GPS) surveys in northwestern Sumatra combined with in situ and remote observations of the vertical motion of coral reefs. These data show that the earthquake was generated by rupture of the Sunda subduction megathrust over a distance of >1,500 kilometres and a width of <150 kilometres. Megathrust slip exceeded 20 metres offshore northern Sumatra, mostly at depths shallower than 30 kilometres. Comparison of the geodetically and seismically inferred slip distribution indicates that approximately 30 per cent additional fault slip accrued in the 1.5 months following the 500-second-long seismic rupture. Both seismic and aseismic slip before our re-occupation of GPS sites occurred on the shallow portion of the megathrust, where the large Aceh tsunami originated. Slip tapers off abruptly along strike beneath Simeulue Island at the southeastern edge of the rupture, where the earthquake nucleated and where an M(w) = 7.2 earthquake occurred in late 2002. This edge also abuts the northern limit of slip in the 28 March 2005 M(w) = 8.7 Nias-Simeulue earthquake.

Practice effects predict cognitive outcome in amnestic mild cognitive impairment.

OBJECTIVE: Practice effects on cognitive tests have been shown to further characterize patients with amnestic mild cognitive impairment (aMCI) and may provide predictive information about cognitive change across time. We tested the hypothesis that a loss of practice effects would portend a worse prognosis in aMCI. DESIGN: Longitudinal, observational design following participants across 1 year. SETTING: Community-based cohort. PARTICIPANTS: Three groups of older adults: 1) cognitively intact (n = 57), 2) aMCI with large practice effects across 1 week (MCI + PE, n = 25), and 3) aMCI with minimal practice effects across 1 week (MCI - PE, n = 26). MEASUREMENTS: Neuropsychological tests. RESULTS: After controlling for age and baseline cognitive differences, the MCI - PE group performed significantly worse than the other groups after 1 year on measures of immediate memory, delayed memory, language, and overall cognition. CONCLUSIONS: Although these results need to be replicated in larger samples, the loss of short-term practice effects portends a worse prognosis in patients with aMCI.

Comparison of computerized versus booklet versions of the TOMM™.

This study examined whether there is a significant difference in performance on two different versions of the Test of Memory Malingering (TOMM; Tombaugh, 1996). Differences in performance were compared between the examiner-administered booklet version versus the self-administered computerized version. No statistically significant differences were found between performance on the two versions. These data indicate that the two versions of the TOMM produce equivalent performance, at least among college students. Further studies employing other populations are warranted.

Occupational exposure to PCBs reduces striatal dopamine transporter densities only in women: a beta-CIT imaging study.

We hypothesize that occupational exposure to PCBs is associated with a reduction in central dopamine (DA) similar to changes previously seen in PCB exposed adult non-human primates. To test that hypothesis, we used [(123)I]beta-CIT SPECT imaging to estimate basal ganglia DA transporter density in former capacitor workers. Women, but not men, showed an inverse relationship between lipid-adjusted total serum PCB concentrations and DA transporter densities in the absence of differences in serum PCB concentrations. These sex differences may reflect age-related reductions in the levels of gonadal hormones since these hormones have been shown experimentally to alter response to DA neurotoxicants. These findings may aid in better understanding the roles that sex and age play in modifying central DA function following exposure, not only to PCBs, but also to other DA neurotoxicants as well as further elucidating the role of gonadal hormones in influencing the initiation and/or progression of neurodegenerative disorders.

Evidence of an age-related threshold effect of polychlorinated biphenyls (PCBs) on neuropsychological functioning in a Native American population.

Polychlorinated biphenyls (PCBs) have been suspected for some time of having adverse effects on neuropsychological functioning in humans. While there is evidence of slowing of cognitive function in children associated with exposure to PCBs, the evidence of comparable effects on adults is far less well understood. We report here on the neuropsychological evaluation of 277 Native American adults, ranging in age from 18 to 79, who were exposed to PCBs by way of environmental contamination in the St. Lawrence region of upstate New York. PCB body burden was estimated by 101 PCB congeners and neuropsychological functioning was assessed by a battery of 18 tests. Spline regression models were fitted to the latent variables of memory, motor function, and higher-order executive functioning. After adjusting for age, gender, and education the analyses revealed a threshold effect of PCBs at approximately 2 ppb. An age-by-PCB interaction effect was also observed for several variables which suggests that the threshold effect was largely confined to the age range of 40-79 and was not observable in the 18-40-year-old group. Implications of these results are discussed in comparison to previously published similar work with adults and in terms of its potential clinical meaningfulness.

Motor tests and cognition in healthy older adults.

UNLABELLED: The Finger Tapping Test (FTT) and Grooved Pegboard Test (GPT) are commonly used in neuropsychological assessments. The performance of healthy older adults on these tasks has not been well characterized in the existing literature. The present study examines FTT and GPT performance in a sample of 307 community-dwelling older individuals (ages 55-74) with no neurological or psychiatric history. RESULTS: FTT performance was influenced by age, gender, and education, while GPT performance was influenced by age and gender. Findings are presented for both hands, as well as dominant-to-non-dominant hand ratio score, on each test. Correlations with other neuropsychological measures demonstrated that the GPT is more strongly correlated with measures of most domains (memory, processing speed, executive functioning, and spatial organization) than the FTT. CONCLUSIONS: While the FTT can be used to measure upper extremity motor ability, the GPT may be more strongly associated with general cognitive functioning in healthy adults. The FTT and GPT results presented will improve the utility of these tasks in clinical assessments of older adults.

Polychlorinated biphenyl exposure and neuropsychological status among older residents of upper Hudson River communities.

BACKGROUND: Polychlorinated biphenyls (PCBs) may accelerate the cognitive and motor dysfunction found in normal aging, but few studies have examined these outcomes and PCB exposure among older adults. OBJECTIVE: We evaluated neuropsychological status and low-level PCB exposure among older adults living along contaminated portions of the upper Hudson River in New York. METHODS: A total of 253 persons between 55 and 74 years of age were recruited and interviewed, and provided blood samples for congener-specific PCB analysis. Participants also underwent a neuropsychological battery consisting of 34 tests capable of detecting subtle deficits in cognition, motor function, affective state, and olfactory function. RESULTS: After adjustment for potential confounders, the results indicated that an increase in serum total PCB concentration from 250 to 500 ppb (lipid basis) was associated with a 6.2% decrease in verbal learning, as measured by California Verbal Learning Test trial 1 score (p = 0.035), and with a 19.2% increase in depressive symptoms, as measured by the Beck Depression Inventory (p = 0.007). CONCLUSIONS: The results suggest that exposure to PCBs may be associated with some measures of memory and learning and depression among adults 55-74 years of age whose current body burdens are similar to those of the general population. Although the results are useful in delineating the neuropsychological effects of low-level exposure to PCBs, further studies of whether older men and women are a sensitive subpopulation are needed.

Clinical utility of Trial 1 of the Test of Memory Malingering (TOMM).

The clinical utility of Trial 1 of the Test of Memory Malingering (TOMM) has recently become a topic of investigation. The current study cross-validated previous research suggesting that those participants who score 45 or greater on Trial 1 of the TOMM will continue to do so on Trial 2 and the Retention Trial and extended these findings to broader clinical and nonclinical populations. Two archival samples were included for analyses: one sample of healthy community-dwelling elders and another sample drawn from an outpatient neuropsychology clinic. As demonstrated previously, 100% of those patients that scored 45 or greater on TOMM Trial 1 scored above cut-scores on Trial 2 and the Retention Trial, supporting the utility of a possible discontinuation rule on Trial 1. When combined with previous research, the current results provide further support for the clinical utility of Trial 1 in predicting overall performance on the TOMM; however, use of any nonstandard administration of the TOMM may not satisfy Daubert criteria in forensic settings and may not be appropriate.

Performance and Symptom Validity Testing in Pediatric Assessment: A Review of the Literature.

There has been an increased recognition that validity testing is an integral component of evaluations conducted with youth. The incorporation of validity testing provides an objective basis for placing confidence in the test data as an accurate assessment of the child's or adolescent's current ability level and/or an accurate indication of the child's or adolescent's current symptoms or behavioral functioning. The use of objective performance validity and symptom validity is consistent with the current emphasis of data-driven decision-making. This paper provides a review of the literature on performance and symptom validity tests for children and adolescents. The strengths and limitations of the available validity tests are discussed, and recommendations for use in pediatric assessments are provided.

A Generalizable, Data-Driven Approach to Predict Daily Risk of Clostridium difficile Infection at Two Large Academic Health Centers.

OBJECTIVE An estimated 293,300 healthcare-associated cases of Clostridium difficile infection (CDI) occur annually in the United States. To date, research has focused on developing risk prediction models for CDI that work well across institutions. However, this one-size-fits-all approach ignores important hospital-specific factors. We focus on a generalizable method for building facility-specific models. We demonstrate the applicability of the approach using electronic health records (EHR) from the University of Michigan Hospitals (UM) and the Massachusetts General Hospital (MGH). METHODS We utilized EHR data from 191,014 adult admissions to UM and 65,718 adult admissions to MGH. We extracted patient demographics, admission details, patient history, and daily hospitalization details, resulting in 4,836 features from patients at UM and 1,837 from patients at MGH. We used L2 regularized logistic regression to learn the models, and we measured the discriminative performance of the models on held-out data from each hospital. RESULTS Using the UM and MGH test data, the models achieved area under the receiver operating characteristic curve (AUROC) values of 0.82 (95% confidence interval [CI], 0.80-0.84) and 0.75 ( 95% CI, 0.73-0.78), respectively. Some predictive factors were shared between the 2 models, but many of the top predictive factors differed between facilities. CONCLUSION A data-driven approach to building models for estimating daily patient risk for CDI was used to build institution-specific models at 2 large hospitals with different patient populations and EHR systems. In contrast to traditional approaches that focus on developing models that apply across hospitals, our generalizable approach yields risk-stratification models tailored to an institution. These hospital-specific models allow for earlier and more accurate identification of high-risk patients and better targeting of infection prevention strategies. Infect Control Hosp Epidemiol 2018;39:425-433.

The influence of an adaptation period in reducing the third party observer effect during a neuropsychological evaluation.

Individuals have been shown to perform suboptimally on memory measures when a third party observer (TPO) is present. The current study attempted to use adaptation to reduce the inhibitory effect of a TPO on memory performance. Undergraduate participants (N=80) were randomly assigned to one of four groups in a 2 x 2 (+/-adaptation period, +/-observation) design in order to investigate the interaction between adaptation period and observation status. Results indicated that the adaptation period had a negligible inhibitory effect over the recall of observed participants (d= -0.11), but unexpectedly, when unobserved participants were not given an adaptation period, recall was inhibited by a sizeable degree (d= -1.11). These findings suggest that the presence of the TPO may have prevented participants from benefiting from adaptation to the general testing situation. To date, there are no known methods for eliminating the TPO effect.

Practice effects in the prediction of long-term cognitive outcome in three patient samples: a novel prognostic index.

Practice effects, defined as improvements in cognitive test performance due to repeated exposure to the test materials, have traditionally been viewed as sources of error. However, they might provide useful information for predicting cognitive outcome. The current study used three separate patient samples (older adults with mild cognitive impairments, individuals who were HIV+, individuals with Huntington's disease) to examine the relationship between practice effects and cognitive functioning at a later point. Across all three samples, practice effects accounted for as much as 31-83% of the variance in the follow-up cognitive scores, after controlling for baseline cognitive functioning. If these findings can be replicated in other patients with neurodegenerative disorders, clinicians and researchers may be able to develop predictive models to identify the individuals who are most likely to demonstrate continued cognitive decline across time. The ability to utilize practice effects data would add a simple, convenient, and non-invasive marker for monitoring an individual patient's cognitive status. Additionally, this prognostic index could be used to offer interventions to patients who are in the earliest stages of progressive neurodegenerative disorders.

Examining the Test Of Memory Malingering Trial 1 and Word Memory Test Immediate Recognition as screening tools for insufficient effort.

Assessing effort level during neuropsychological evaluations is critical to support the accuracy of cognitive test scores. Many instruments are designed to measure effort, yet they are not routinely administered in neuropsychological assessments. The Test of Memory Malingering (TOMM) and the Word Memory Test (WMT) are commonly administered symptom validity tests with sound psychometric properties. This study examines the use of the TOMM Trial 1 and the WMT Immediate Recognition (IR) trial scores as brief screening tools for insufficient effort through an archival analysis of a combined sample of mild head-injury litigants ( N = 105) who were assessed in forensic private practices. Results show that both demonstrate impressive diagnostic accuracy and calculations of positive and negative predictive power are presented for a range of base rates. These results support the utility of Trial 1 of the TOMM and the WMT IR trial as screening methods for the assessment of insufficient effort in neuropsychological assessments.

Not all performance validity tests are created equal: The role of recollection and familiarity in the Test of Memory Malingering and Word Memory Test.

INTRODUCTION: The Test of Memory Malingering (TOMM) and the Word Memory Test (WMT) are both performance validity tests (PVTs) that use a two-alternative forced-choice (2AFC) recognition memory format. Several studies have reported that these tests are susceptible to cognitive impairment and that the WMT is more susceptible than the TOMM. The current study explored components of recognition memory (i.e., conscious recollection and familiarity) underlying the TOMM and WMT to identify factors that make them susceptible and resilient to cognitive impairment. METHOD: Fifty-four nonclinical undergraduate research participants were administered the TOMM and WMT while providing introspective judgments about their recognition memory using the remember/know/guess procedure. In addition, half of participants were administered dual-task interference, a manipulation intended to reduce recollection, during these tests, while the other half completed these tests without interference. Standard cutoffs on the TOMM and WMT were explored, as well as alternative cutoffs based on TOMM Trial 1 scores. RESULTS: The WMT was more impacted by dual-task interference than standard TOMM cutoff trials, while alternative TOMM cutoff trials were equally impacted by dual-task interference relative to the WMT. Dual-task interference reduced recollection on these tests, but spared familiarity. Standard TOMM trials and the WMT were relatively comparable on levels of recollection, but familiarity contributed more to the TOMM than to the WMT. Alternative TOMM trials possessed lower familiarity and recollection than standard TOMM trials and lower recollection than the WMT. CONCLUSIONS: Reduced recollection places examinees at risk of failing the TOMM and WMT, while familiarity contributes to the relative resilience of the standard TOMM. Future development of 2AFC recognition memory PVTs should attempt to maximize the contribution of familiarity to their completion.

Perfluoroalkyl substances, thyroid hormones, and neuropsychological status in older adults.

Minimal data exist regarding the neurotoxicity of perfluoroalkyl substances (PFASs) in aging populations and the possible mediating effects of thyroid hormones (THs). Hence, the aims of this study were to: (i) assess associations between PFASs and neuropsychological function, and (ii) determine if such associations are mediated by changes in circulating THs in an aging population. We measured perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), total thyroxine (T4) and free thyroxine (fT4) in serum and performed neuropsychological tests in 126 men and women aged 55-74 years and living in upper Hudson River communities. Multivariable linear regressions were conducted to assess associations between PFASs and neuropsychological test scores. Mediation analyses were performed in a subset of 87 participants for whom information was available on both PFASs and THs. We calculated TH-mediated, non-TH mediated, and total effects of PFASs on neuropsychological test scores. Higher PFOA was associated with better performance in tasks of the California Verbal Learning Test and the Wisconsin Card Sorting Test. Higher PFOS was associated with improved performance in a Wechsler Memory Scale subtest and Block Design Subtest (BDT) total scores. There was no evidence of mediation by THs for PFOA-neuropsychological function associations. However, T4 and fT4 partially mediated the protective effect of PFOS on BDT total scores. Our findings do not suggest that PFASs are associated with poor neuropsychological function. There was some evidence of mediation for the association between PFASs and neuropsychological functions by THs, although some other modes of action also appear likely.

Coverage of the Test of Memory Malingering, Victoria Symptom Validity Test, and Word Memory Test on the Internet: is test security threatened?

In forensic neuropsychological settings, maintaining test security has become critically important, especially in regard to symptom validity tests (SVTs). Coaching, which can entail providing patients or litigants with information about the cognitive sequelae of head injury, or teaching them test-taking strategies to avoid detection of symptom dissimulation has been examined experimentally in many research studies. Emerging evidence supports that coaching strategies affect psychological and neuropsychological test performance to differing degrees depending on the coaching paradigm and the tests administered. The present study sought to examine Internet coverage of SVTs because it is potentially another source of coaching, or information that is readily available. Google searches were performed on the Test of Memory Malingering, the Victoria Symptom Validity Test, and the Word Memory Test. Results indicated that there is a variable amount of information available about each test that could threaten test security and validity should inappropriately interested parties find it. Steps that could be taken to improve this situation and limitations to this exploration are discussed.

Potential for interpretation disparities of Halstead-Reitan neuropsychological battery performances in a litigating sample.

The performances of 110 litigants on seven variables from the Halstead-Reitan neuropsychological battery (HRNB) were used to compare Heaton, Miller, Taylor, and Grant's (2004) Deficit Scale (DS) and Reitan and Wolfson's (1993) Neuropsychological Deficit Scale (NDS). Additional comparisons were made for people who passed or failed the Test of Memory Malingering (TOMM) to determine effects of effort on scores generated by either scoring system. Wilcoxon signed-rank tests revealed that all seven comparisons were significantly different for the full sample (p< or =0.001). The NDS indicated greater levels of impairment compared to DS across all variables. These findings were also obtained when considering effort, though TOMM failure was related to non-significant differences for two variables. These findings suggest that the two scoring systems are not equivalent, with Heaton et al.'s DS resulting in consistently higher identification rates of normal brain functioning compared to those generated from Reitan and Wolfson's NDS system.

Validation of Victoria Symptom Validity Test Cutoff Scores among Mild Traumatic Brain Injury Litigants Using a Known-Groups Design.

The Victoria Symptom Validity Test (VSVT) is one of the most accurate performance validity tests. Previous research has recommended several cutoffs for performance invalidity classification on the VSVT. However, only one of these studies used a known groups design and no study has investigated these cutoffs in an exclusively mild traumatic brain injury (mTBI) medico-legal sample. The current study used a known groups design to validate VSVT cutoffs among mild traumatic brain injury litigants and explored the best approach for using the multiple recommended cutoffs for this test. Cutoffs of <18 Hard items correct, <41 Total items correct, an Easy - Hard items correct difference >6, and <5 items correct on any block yielded the strongest classification accuracy. Using multiple cutoffs in conjunction reduced classification accuracy. Given convergence across studies, a cutoff of <18 Hard items correct is the most appropriate for use with mTBI litigants.

Thyroid function and neuropsychological status in older adults.

Overt thyroid dysfunction is recognized as a risk factor for neuropsychological deficits in aging populations, yet evidence for how changes in levels of circulatory thyroid hormones impact specific neuropsychological domains is limited. Here we report cross-sectional associations between serum thyroid hormone concentrations and several neuropsychological function domains among men and women aged 55-74years. We administered neuropsychological tests to assess memory, learning, executive function, measures of attention, visuospatial function, affective state, and motor function. Multivariable linear regression analyses were performed adjusting for age, sex, education, and cigarette smoking. Effects were reported as differences in test scores per one interquartile range (IQR) increase in hormone concentration. Higher total thyroxine (T4) and free thyroxine (fT4) were associated with improved visuospatial function, as measured by Block Design Subtest total scores; associated increments per IQR differences in T4 and fT4 were 15% and 19%, respectively (false discovery rate q-values <0.05). We also detected statistical interactions between age and fT4 for effects in tasks of memory and learning. Concurrent increases in age and fT4 were associated with deficits in memory and learning as measured by California Verbal Learning Test subtests (10% and 16% deficits in t-score and short delay free recall score, respectively). Our findings suggest that changes in thyroid hormones may have important implications for neuropsychological function in aging populations. Further large-scale studies with comprehensive thyroid function and neuropsychological outcome assessments are warranted to confirm these results.