Correction: Analysis of fetal DNA in maternal plasma with markers designed for forensic DNA mixture resolution.

In the original version of this Article, the data for Mother ID 8; 13; 25; 31; and 47 of Table 2 was merged. This has now been corrected in both the PDF and HTML versions of the Article.

Analysis of fetal DNA in maternal plasma with markers designed for forensic DNA mixture resolution.

PURPOSE: With the description of circulating fetal DNA in maternal blood, noninvasive prenatal diagnostics became theoretically possible. As the presence of background maternal DNA interferes with the detection of fetal DNA, analytical methods require genetic markers capable of distinguishing by quantitative or targeted approaches the minor population of DNA molecules of the fetus. Here we evaluate the feasibility of analyzing fetal DNA with novel DIP-STR genetic markers, designed for the investigation of forensic mixed biological evidence. METHODS: The DIP-STR molecular approach is based on sequence-specific analysis of paternally inherited fetal alleles. These sequences are biallelic deletion/insertion polymorphisms (DIPs) located very close to short tandem repeat (STR) markers, for combined analysis. In this study, 48 women were tested with 28 DIP-STRs during the first, second, and third trimester of pregnancy. RESULTS: Positive results were obtained across markers, including longer ones (386 base-pairs) and with blood samples collected during early pregnancy, such as 10 weeks of gestational age. CONCLUSION: These data show that DIP-STR markers can be used to amplify specific genomic regions of circulating fetal DNA to obtain targeted genetic information. This method may contribute to developments in noninvasive prenatal paternity testing and diagnosis of certain genetic diseases.

meaRtools: An R package for the analysis of neuronal networks recorded on microelectrode arrays.

Here we present an open-source R package 'meaRtools' that provides a platform for analyzing neuronal networks recorded on Microelectrode Arrays (MEAs). Cultured neuronal networks monitored with MEAs are now being widely used to characterize in vitro models of neurological disorders and to evaluate pharmaceutical compounds. meaRtools provides core algorithms for MEA spike train analysis, feature extraction, statistical analysis and plotting of multiple MEA recordings with multiple genotypes and treatments. meaRtools functionality covers novel solutions for spike train analysis, including algorithms to assess electrode cross-correlation using the spike train tiling coefficient (STTC), mutual information, synchronized bursts and entropy within cultured wells. Also integrated is a solution to account for bursts variability originating from mixed-cell neuronal cultures. The package provides a statistical platform built specifically for MEA data that can combine multiple MEA recordings and compare extracted features between different genetic models or treatments. We demonstrate the utilization of meaRtools to successfully identify epilepsy-like phenotypes in neuronal networks from Celf4 knockout mice. The package is freely available under the GPL license (GPL> = 3) and is updated frequently on the CRAN web-server repository. The package, along with full documentation can be downloaded from: https://cran.r-project.org/web/packages/meaRtools/.

DIP-STR: highly sensitive markers for the analysis of unbalanced genomic mixtures.

Samples containing highly unbalanced DNA mixtures from two individuals commonly occur both in forensic mixed stains and in peripheral blood DNA microchimerism induced by pregnancy or following organ transplant. Because of PCR amplification bias, the genetic identification of a DNA that contributes trace amounts to a mixed sample represents a tremendous challenge. This means that standard genetic markers, namely microsatellites, also referred as short tandem repeats (STR), and single-nucleotide polymorphism (SNP) have limited power in addressing common questions of forensic and medical genetics. To address this issue, we developed a molecular marker, named DIP-STR that relies on pairing deletion-insertion polymorphisms (DIP) with STR. This novel analytical approach allows for the unambiguous genotyping of a minor component in the presence of a major component, where DIP-STR genotypes of the minor were successfully procured at ratios up to 1:1,000. The compound nature of this marker generates a high level of polymorphism that is suitable for identity testing. Here, we demonstrate the power of the DIP-STR approach on an initial set of nine markers surveyed in a Swiss population. Finally, we discuss the limitations and potential applications of our new system including preliminary tests on clinical samples and estimates of their performance on simulated DNA mixtures.

Cost analysis of a patient navigation system to increase screening colonoscopy adherence among urban minorities.

BACKGROUND: Patient navigation (PN) is being used increasingly to help patients complete screening colonoscopy (SC) to prevent colorectal cancer. At their large, urban academic medical center with an open-access endoscopy system, the authors previously demonstrated that PN programs produced a colonoscopy completion rate of 78.5% in a cohort of 503 patients (predominantly African Americans and Latinos with public health insurance). Very little is known about the direct costs of implementing PN programs. The objective of the current study was to perform a detailed cost analysis of PN programs at the authors' institution from an institutional perspective. METHODS: In 2 randomized controlled trials, average-risk patients who were referred for SC by primary care providers were recruited for PN between May 2008 and May 2010. Patients were randomized to 1 of 4 PN groups. The cost of PN and net income to the institution were determined in a cost analysis. RESULTS: Among 395 patients who completed colonoscopy, 53.4% underwent SC alone, 30.1% underwent colonoscopy with biopsy, and 16.5% underwent snare polypectomy. Accounting for the average contribution margins of each procedure type, the total revenue was $95,266.00. The total cost of PN was $14,027.30. Net income was $81,238.70. In a model sample of 1000 patients, net incomes for the institutional completion rate (approximately 80%), the historic PN program (approximately 65%), and the national average (approximately 50%) were compared. The current PN program generated additional net incomes of $35,035.50 and $44,956.00, respectively. CONCLUSIONS: PN among minority patients with mostly public health insurance generated additional income to the institution, mainly because of increased colonoscopy completion rates.

Convergent evidence for impaired AKT1-GSK3beta signaling in schizophrenia.

AKT-GSK3beta signaling is a target of lithium and as such has been implicated in the pathogenesis of mood disorders. Here, we provide evidence that this signaling pathway also has a role in schizophrenia. Specifically, we present convergent evidence for a decrease in AKT1 protein levels and levels of phosphorylation of GSK3beta at Ser9 in the peripheral lymphocytes and brains of individuals with schizophrenia; a significant association between schizophrenia and an AKT1 haplotype associated with lower AKT1 protein levels; and a greater sensitivity to the sensorimotor gating-disruptive effect of amphetamine, conferred by AKT1 deficiency. Our findings support the proposal that alterations in AKT1-GSK3beta signaling contribute to schizophrenia pathogenesis and identify AKT1 as a potential schizophrenia susceptibility gene. Consistent with this proposal, we also show that haloperidol induces a stepwise increase in regulatory phosphorylation of AKT1 in the brains of treated mice that could compensate for an impaired function of this signaling pathway in schizophrenia.

Identification and characterization of novel DIP-STRs from whole-genome sequencing data.

In an attempt to enhance forensic DNA mixture deconvolution several alternative DNA typing approaches have been developed. Among these, DIP-STR compound markers can resolve extremely unbalanced two-source DNA mixtures of same-or-opposite sex donors, up to a 1:1000 minor:major DNA ratio. A forensic set of 10 markers was validated for casework and a larger set of 23 DIP-STRs has proven suitable to biogeographic ancestry inference and for prenatal paternity testing. Yet, to promote the widespread use of this original approach, more markers and multiplex panels need to be developed. To this end, here we describe an extended set of forensic DIP-STRs identified using currently available whole-genome sequencing datasets. Complete lists of Indels and STRs were obtained from reported frequencies of genetic variants of 76,156 genomes. About 3000 identified DIP-STRs candidates were shorter than 200 bp and 500 showed high haplotype variability estimated using the genotypes of individuals homozygous for the DIP or the STR. Here, we present 23 additional DIP-STRs validated for sensitivity, specificity and Swiss population variability. Finally, a set of 30 markers comprising seven previously validated ones is proposed for the prospective development of a forensic DIP-STR multiplex panel.

Early noninvasive prenatal paternity testing by targeted fetal DNA analysis.

Today the challenge in paternity testing is to provide an accurate noninvasive assay that can be performed early during pregnancy. This requires the use of novel analytical methods capable of detecting the low fraction of circulating fetal DNA in maternal blood. We previously showed that forensic compound markers such as deletion/insertion polymorphisms-short tandem repeats (DIP-STR) can efficiently resolve complex mixed biological evidence including the target analysis of paternally inherited fetal alleles. In this study, we describe for the first time the validation of this type of markers in the first trimester of pregnancies, in addition to defining the statistical framework to evaluate paternity. To do so, we studied 47 DIP-STRs in 87 cases, with blood samples collected throughout gestation starting from the seven weeks of amenorrhea. Fetal DNA detection in the first trimester shows a false negative rate as low as 6%. The combined paternity index (CPI) results indicate that seven markers with fully informative genotypes are sufficient to determine the paternity. This study demonstrates that DIP-STR markers can be used from early pregnancy and that a small set of markers (about 40) is sufficient to address the question of paternity. The novel method offers substantial improvements over similar approaches in terms of reduced number of markers, lower costs and increased accuracy.

An mHealth Text Messaging Program Providing Symptom Detection Training and Psychoeducation to Improve Hypoglycemia Self-Management: Intervention Development Study.

BACKGROUND: Hypoglycemia remains a challenge for roughly 25% of people with type 1 diabetes (T1D) despite using advanced technologies such as continuous glucose monitors (CGMs) or automated insulin delivery systems. Factors impacting hypoglycemia self-management behaviors (including reduced ability to detect hypoglycemia symptoms and unhelpful hypoglycemia beliefs) can lead to hypoglycemia development in people with T1D who use advanced diabetes technology. OBJECTIVE: This study aims to develop a scalable, personalized mobile health (mHealth) behavioral intervention program to improve hypoglycemia self-management and ultimately reduce hypoglycemia in people with T1D who use advanced diabetes technology. METHODS: We (a multidisciplinary team, including clinical and health psychologists, diabetes care and education specialists, endocrinologists, mHealth interventionists and computer engineers, qualitative researchers, and patient partners) jointly developed an mHealth text messaging hypoglycemia behavioral intervention program based on user-centered design principles. The following five iterative steps were taken: (1) conceptualization of hypoglycemia self-management processes and relevant interventions; (2) identification of text message themes and message content development; (3) message revision; (4) patient partner assessments for message readability, language acceptability, and trustworthiness; and (5) message finalization and integration with a CGM data-connected mHealth SMS text message delivery platform. An mHealth web-based SMS text message delivery platform that communicates with a CGM glucose information-sharing platform was also developed. RESULTS: The mHealth SMS text messaging hypoglycemia behavioral intervention program HypoPals, directed by patients' own CGM data, delivers personalized intervention messages to (1) improve hypoglycemia symptom detection and (2) elicit self-reflection, provide fact-based education, and suggest practical health behaviors to address unhelpful hypoglycemia beliefs and promote hypoglycemia self-management. The program is designed to message patients up to 4 times per day over a 10-week period. CONCLUSIONS: A rigorous conceptual framework, a multidisciplinary team (including patient partners), and behavior change techniques were incorporated to create a scalable, personalized mHealth SMS text messaging behavioral intervention. This program was systematically developed to improve hypoglycemia self-management in advanced diabetes technology users with T1D. A clinical trial is needed to evaluate the program's efficacy for future clinical implementation.

Challenges to replicating evidence-based research in real-world settings: training African-American peers as patient navigators for colon cancer screening.

Many cancer-prevention interventions have demonstrated effectiveness in diverse populations, but these evidenced-based findings slowly disseminate into practice. The current study describes the process of disseminating and replicating research (i.e., peer patient navigation for colonoscopy screening) in real-world settings. Two large metropolitan hospitals collaborated to replicate a peer patient navigation model within their existing navigation systems. Six African-American peer volunteers were recruited and trained to navigate patients through colonoscopy scheduling and completion. Major challenges included: (1) operating within multiple institutional settings; (2) operating within nonacademic/research infrastructures; (3) integrating into an established navigation system; (4) obtaining support of hospital staff without overburdening; and (5) competing priorities and time commitments. Bridging the gap between evidence-based research and practice is critical to eliminating many cancer health disparities; therefore, it is crucial that researchers and practitioners continue to work to achieve both diffusion and fusion of evidence-based findings. Recommendations for addressing these challenges are discussed.

Increasing the efficiency of randomized trial estimates via linear adjustment for a prognostic score.

Estimating causal effects from randomized experiments is central to clinical research. Reducing the statistical uncertainty in these analyses is an important objective for statisticians. Registries, prior trials, and health records constitute a growing compendium of historical data on patients under standard-of-care that may be exploitable to this end. However, most methods for historical borrowing achieve reductions in variance by sacrificing strict type-I error rate control. Here, we propose a use of historical data that exploits linear covariate adjustment to improve the efficiency of trial analyses without incurring bias. Specifically, we train a prognostic model on the historical data, then estimate the treatment effect using a linear regression while adjusting for the trial subjects' predicted outcomes (their prognostic scores). We prove that, under certain conditions, this prognostic covariate adjustment procedure attains the minimum variance possible among a large class of estimators. When those conditions are not met, prognostic covariate adjustment is still more efficient than raw covariate adjustment and the gain in efficiency is proportional to a measure of the predictive accuracy of the prognostic model above and beyond the linear relationship with the raw covariates. We demonstrate the approach using simulations and a reanalysis of an Alzheimer's disease clinical trial and observe meaningful reductions in mean-squared error and the estimated variance. Lastly, we provide a simplified formula for asymptotic variance that enables power calculations that account for these gains. Sample size reductions between 10% and 30% are attainable when using prognostic models that explain a clinically realistic percentage of the outcome variance.

Peroxisomal and microsomal lipid pathways associated with resistance to hepatic steatosis and reduced pro-inflammatory state.

Accumulation of fat in the liver increases the risk to develop fibrosis and cirrhosis and is associated with development of the metabolic syndrome. Here, to identify genes or gene pathways that may underlie the genetic susceptibility to fat accumulation in liver, we studied A/J and C57Bl/6 mice that are resistant and sensitive to diet-induced hepatosteatosis and obesity, respectively. We performed comparative transcriptomic and lipidomic analysis of the livers of both strains of mice fed a high fat diet for 2, 10, and 30 days. We found that resistance to steatosis in A/J mice was associated with the following: (i) a coordinated up-regulation of 10 genes controlling peroxisome biogenesis and ß-oxidation; (ii) an increased expression of the elongase Elovl5 and desaturases Fads1 and Fads2. In agreement with these observations, peroxisomal ß-oxidation was increased in livers of A/J mice, and lipidomic analysis showed increased concentrations of long chain fatty acid-containing triglycerides, arachidonic acid-containing lysophosphatidylcholine, and 2-arachidonylglycerol, a cannabinoid receptor agonist. We found that the anti-inflammatory CB2 receptor was the main hepatic cannabinoid receptor, which was highly expressed in Kupffer cells. We further found that A/J mice had a lower pro-inflammatory state as determined by lower plasma levels and IL-1ß and granulocyte-CSF and reduced hepatic expression of their mRNAs, which were found only in Kupffer cells. This suggests that increased 2-arachidonylglycerol production may limit Kupffer cell activity. Collectively, our data suggest that genetic variations in the expression of peroxisomal ß-oxidation genes and of genes controlling the production of an anti-inflammatory lipid may underlie the differential susceptibility to diet-induced hepatic steatosis and pro-inflammatory state.

Further insight into the global variability of the OCA2-HERC2 locus for human pigmentation from multiallelic markers.

The OCA2-HERC2 locus is responsible for the greatest proportion of eye color variation in humans. Numerous studies extensively described both functional SNPs and associated patterns of variation over this region. The goal of our study is to examine how these haplotype structures and allelic associations vary when highly variable markers such as microsatellites are used. Eleven microsatellites spanning 357 Kb of OCA2-HERC2 genes are analyzed in 3029 individuals from worldwide populations. We found that several markers display large differences in allele frequency (10% to 35% difference) among Europeans, East Asians and Africans. In Europe, the alleles showing increased frequency can also discriminate individuals with (IrisPlex) predicted blue and brown eyes. Distinct haplotypes are identified around the variants C and T of the functional SNP rs12913832 (associated to blue eyes), with linkage disequilibrium r2 values significant up to 237 Kb. The haplotype carrying the allele rs12913832 C has high frequency (76%) in blue eye predicted individuals (30% in brown eye predicted individuals), while the haplotype associated to the allele rs12913832 T is restricted to brown eye predicted individuals. Finally, homozygosity values reach levels of 91% near rs12913832. Odds ratios show values of 4.2, 7.4 and 10.4 for four markers around rs12913832 and 7.1 for their core haplotype. Hence, this study provides an example on the informativeness of multiallelic markers that, despite their current limited potential contribution to forensic eye color prediction, supports the use of microsatellites for identifying causing variants showing similar genetic features and history.

Inferring biogeographic ancestry with compound markers of slow and fast evolving polymorphisms.

Bio-geographic ancestry is an area of considerable interest in the medical genetics, anthropology and forensics. Although genome-wide panels are ideal as they provide dense genotyping data, small sets of ancestry informative marker provide a cost-effective way to investigate genetic ancestry and population structure. Here, we investigate the performance of a reduced marker set that combine different types of autosomal markers through haplotype analysis. In particular, recently described DIP-STR markers should offer the advantage of comprising both, low mutation rate Indels (DIPs), to study human history over longer time scale; and high mutation rate STRs, to trace relatively recent demographic events. In this study, we assessed the ability of an initial set of 23 DIP-STRs to distinguish major population groups using the HGDP-CEPH reference samples. The results obtained applying the STRUCTURE algorithm show that the discrimination capacity of the DIP-STRs is comparable to currently used small-scale ancestry informative markers by approaching seven major demographic groups. Yet, the DIP-STRs show an improved success rate in assigning individuals to populations of Europe and Middle East. These data show a remarkable ability of a preliminary set of 23 DIP-STR markers to infer major biogeographic origins. A novel set of DIP-STRs preselected to contain ancestry information should lead to further improvements.

Application of DIP-STRs to sexual/physical assault investigations: Eight case reports.

DIP-STRs are compound markers formed by a deletion/insertion polymorphism linked to a microsatellite. They enable the deconvolution of unbalanced DNA mixtures from two individuals, up to 1000 fold excess of one contributor. In practice, this novel tool allows to test for the presence of a DNA of interest in traces appearing not useful because of the masking effect of the major DNA contributor. Thus far two sets of DIP-STRs have been published: the first set was described as proof-of-principle, while the second set was specifically developed for forensic applications. Here, we report on the first use of these markers in casework to show advantages and limitations in real examples. Traces, suggestive of containing unbalanced DNA mixtures (beyond standard STR mixture resolution), were selected from eight cases submitted to the Forensic Genetics Unit of the University Center of Legal Medicine of Lausanne-Geneva. Using 18 validated DIP-STRs, two to ten markers were selected for each case. A minor DNA contributor - undetected using conventional STRs - was detected for the trace samples of six cases. DIP-STR results contributed to each case, either by complementing Y-STRs results or by producing novel investigative leads. This was especially true with same sex unbalanced DNA mixtures, female minor/male major unbalanced DNA mixtures or when the source of the DNA mixture was said to come either from the suspect and the female complainant or from his brother and the female complainant. Interestingly, these markers were found to be more sensitive and specific than previously known. Positive results were obtained at 16,000-fold excess of major DNA using few picograms of input DNA, as well as from traces collected several months after the alleged offence. Likelihood ratios assigned to measure the strength of DIP-STRs' DNA evidence were modest (10), when accounted by only two DIP-STRs, and high (106) when determined by six markers. In some cases the detection of extra alleles from additional minor DNA contributors or because of extremely unbalanced DNA ratios, limited the interpretation of the results. In conclusion, the DIP-STRs often provide additional value to the analysis of traces that cannot be exploited by the use of standard methods.

Sensitive DIP-STR markers for the analysis of unbalanced mixtures from "touch" DNA samples.

Casework samples collected for forensic DNA analysis can produce genomic mixtures in which the DNA of the alleged offender is masked by high quantities of DNA coming from the victim. DIP-STRs are novel genetic markers specifically developed to enable the target analysis of a DNA of interest in the presence of exceeding quantities of a second DNA (up to 1000-fold). The genotyping system, which is based on allele-specific amplifications of haplotypes formed by a deletion/insertion polymorphism (DIP) and a short tandem repeat (STR), combines the capacity of targeting the DNA of an individual with a strong identification power. Finally, DIP-STRs are autosomal markers therefore they can be applied to any combination of major and minor DNA. In this study we aimed to assess the ability of DIP-STRs to detect the minor contributor on challenging "touch" DNA samples simulated with representative crime-associated substrates and to compare their performance to commonly used male-specific markers (Y-STRs). As part of a comprehensive study on the relative DNA contribution of two persons handling the same object, we selected 71 unbalanced contact traces of which 14 comprised a male minor DNA contributor mixed to a female major DNA contributor. Using a set of six DIP-STRs, one to four markers were found to be informative for the minor DNA detection across traces. When compared to Y-STRs (14 traces), the DIP-STRs showed similar sensitivity in detecting the minor DNA across substrate materials with a similar occurrence of allele drop-out. Conversely, because of the sex combination of the two users of the object, 57 remaining traces could only be investigated by DIP-STRs. Of these, 30 minor DNA contributors could be detected by all informative markers while 12 traces showed events of allele drop-out. Finally, 15 traces showed no amplification of the minor DNA. These last 15 samples were mostly characterized by a combination of short handling time of the object, low DNA recovery and/or one single informative DIP-STR. In conclusion, the DIP-STRs represent alternative markers to help solving unbalanced two-source DNA mixtures, and also those produced from contact stains. These markers, in addition to a novel set of 10 DIP-STRs specifically developed according to forensic technical standards, will offer a valuable tool complementary to Y-STR markers.

Characterization of Early Cortical Neural Network Development in Multiwell Microelectrode Array Plates.

We examined neural network ontogeny using microelectrode array (MEA) recordings made in multiwell MEA (mwMEA) plates over the first 12 days in vitro (DIV). In primary cortical cultures, action potential spiking activity developed rapidly between DIV 5 and 12. Spiking was sporadic and unorganized at early DIV, and became progressively more organized with time, with bursting parameters, synchrony, and network bursting increasing between DIV 5 and 12. We selected 12 features to describe network activity; principal components analysis using these features demonstrated segregation of data by age at both the well and plate levels. Using random forest classifiers and support vector machines, we demonstrated that four features (coefficient of variation [CV] of within-burst interspike interval, CV of interburst interval, network spike rate, and burst rate) could predict the age of each well recording with >65% accuracy. When restricting the classification to a binary decision, accuracy improved to as high as 95%. Further, we present a novel resampling approach to determine the number of wells needed for comparing different treatments. Overall, these results demonstrate that network development on mwMEA plates is similar to development in single-well MEAs. The increased throughput of mwMEAs will facilitate screening drugs, chemicals, or disease states for effects on neurodevelopment.

Editor's Highlight: Evaluation of a Microelectrode Array-Based Assay for Neural Network Ontogeny Using Training Set Chemicals.

Thousands of compounds in the environment have not been characterized for developmental neurotoxicity (DNT) hazard. To address this issue, methods to screen compounds rapidly for DNT hazard evaluation are necessary and are being developed for key neurodevelopmental processes. In order to develop an assay for network formation, this study evaluated effects of a training set of chemicals on network ontogeny by measuring spontaneous electrical activity in neural networks grown on microelectrode arrays (MEAs). Rat (0-24 h old) primary cortical cells were plated in 48 well-MEA plates and exposed to 6 compounds: acetaminophen, bisindolylmaleimide-1 (Bis-1), domoic acid, mevastatin, sodium orthovanadate, and loperamide for a period of 12 days. Spontaneous network activity was recorded on days 2, 5, 7, 9, and 12 and viability was assessed using the Cell Titer Blue assay on day 12. Network activity (e.g. mean firing rate [MFR], burst rate [BR], etc), increased between days 5 and 12. Random Forest analysis indicated that across all compounds and times, temporal correlation of firing patterns (r), MFR, BR, number of active electrodes and % of spikes in a burst were the most influential parameters in separating control from treated wells. All compounds except acetaminophen (≤ 30 µM) caused concentration-related effects on one or more of these parameters. Domoic acid and sodium orthovanadate altered several of these parameters in the absence of cytotoxicity. Although cytotoxicity was observed with Bis1, mevastatin, and loperamide, some parameters were affected by these compounds at concentrations below those resulting in cytotoxicity. These results demonstrate that this assay may be suitable for screening of compounds for DNT hazard identification.

In vitro screening of metal oxide nanoparticles for effects on neural function using cortical networks on microelectrode arrays.

Nanoparticles (NPs) may translocate to the brain following inhalation or oral exposures, yet higher throughput methods to screen NPs for potential neurotoxicity are lacking. The present study examined effects of 5 CeO2 (5- 1288 nm), and 4 TiO2 (6-142 nm) NPs and microparticles (MP) on network function in primary cultures of rat cortex on 12 well microelectrode array (MEA) plates. Particles were without cytotoxicity at concentrations ≤50 µg/ml. After recording 1 h of baseline activity prior to particle (3-50 µg/ml) exposure, changes in the total number of spikes (TS) and # of active electrodes (#AEs) were assessed 1, 24, and 48 h later. Following the 48 h recording, the response to a challenge with the GABAA antagonist bicuculline (BIC; 25 µM) was assessed. In all, particles effects were subtle, but 69 nm CeO2 and 25 nm TiO2 NPs caused concentration-related decreases in TS following 1 h exposure. At 48 h, 5 and 69 nm CeO2 and 25 and 31 nm TiO2 decreased #AE, while the two MPs increased #AEs. Following BIC, only 31 nm TiO2 produced concentration-related decreases in #AEs, while 1288 nm CeO2 caused concentration-related increases in both TS and #AE. The results indicate that some metal oxide particles cause subtle concentration-related changes in spontaneous and/or GABAA receptor-mediated neuronal activity in vitro at times when cytotoxicity is absent, and that MEAs can be used to screen and prioritize nanoparticles for neurotoxicity hazard.