Exploratory Development of Algorithms for Determining Driver Attention Status.

OBJECTIVE: Varying driver distraction algorithms were developed using vehicle kinematics and driver gaze data obtained from a camera-based driver monitoring system (DMS). BACKGROUND: Distracted driving characteristics can be difficult to accurately detect due to wide variation in driver behavior across driving environments. The growing availability of information about drivers and their involvement in the driving task increases the opportunity for accurately recognizing attention state. METHOD: A baseline for driver distraction levels was developed using a video feed of 24 separate drivers in varying naturalistic driving conditions. This initial assessment was used to develop four buffer-based algorithms that aimed to determine a driver's real-time attentiveness, via a variety of metrics and combinations thereof. RESULTS: Of those tested, the optimal algorithm included ungrouped glance locations and speed. Notably, as an algorithm's performance of detecting very distracted drivers improved, its accuracy for correctly identifying attentive drivers decreased. CONCLUSION: At a minimum, drivers' gaze position and vehicle speed should be included when designing driver distraction algorithms to delineate between glance patterns observed at high and low speeds. Distraction algorithms should be designed with an understanding of their limitations, including instances in which they may fail to detect distracted drivers, or falsely notify attentive drivers. APPLICATION: This research adds to the body of knowledge related to driver distraction and contributes to available methods to potentially address and reduce occurrences. Machine learning algorithms can build on the data elements discussed to increase distraction detection accuracy using robust artificial intelligence.

Barriers to care in juvenile localized and systemic scleroderma: an exploratory survey study of caregivers' perspectives.

BACKGROUND: Juvenile localized scleroderma (LS) and systemic sclerosis (SSc) are rare pediatric conditions often associated with severe morbidities. Delays in diagnosis are common, increasing the risk for permanent damage and worse outcomes. This study explored caregiver perspectives on barriers they encountered while navigating diagnosis and care for their child's scleroderma. METHODS: In this cross-sectional study, caregivers of juvenile LS or SSc patients were recruited from a virtual family scleroderma educational conference and a juvenile scleroderma online interest group. The survey queried respondents about their child's condition and factors affecting diagnosis and treatment. RESULTS: The response rate was 61% (73/120), with 38 parents of LS patients and 31 parents of SSc patients. Most patients were female (80%) and over half were non-Hispanic white (55%). Most families had at least one person with a college education or higher (87%), traveled ≤ 2 h to see their rheumatologist (83%), and had private insurance (75%). Almost half had an annual household income ≥ $100,000 (46%). Families identified the following factors as barriers to care: lack of knowledge about scleroderma in the medical community, finding reliable information about pediatric scleroderma, long wait times/distances for a rheumatology/specialist appointment, balance of school/work and child's healthcare needs, medication side effects, and identifying effective medications. The barrier most identified as a major problem was the lack of knowledge about juvenile scleroderma in the medical community. Public insurance, household income less than $100,000, and Hispanic ethnicity were associated with specific barriers to care. Lower socioeconomic status was associated with longer travel times to see the rheumatologist/specialist. Diagnosis and systemic treatment initiation occurred at greater than one year from initial presentation for approximately 28% and 36% of patients, respectively. Families of LS patients were commonly given erroneous information about the disease, including on the need and importance of treating active disease with systemic immunosuppressants in patients with deep tissue or rapidly progressive disease. CONCLUSION: Caregivers of children with LS or SSc reported numerous common barriers to the diagnosis, treatment, and ongoing care of juvenile scleroderma. The major problem highlighted was the lack of knowledge of scleroderma within the general medical community. Given that most of the caregiver respondents to the survey had relatively high socioeconomic status, additional studies are needed to reach a broader audience, including caregivers with limited English proficiency, geographical limitations, and financial constraints, to determine if the identified problems are generalizable. Identifying key care barriers will help direct efforts to address needs, reduce disparities in care, and improve patient outcomes.

Effectiveness of a low-cost UVGI chamber for decontaminating filtering facepiece respirators to extend reuse.

In emergencies like the COVID-19 pandemic, the reuse or reprocessing of filtering facepiece respirators (FFRs) may be required to mitigate exposure risk. Research gap: Only a few studies evaluated decontamination effectiveness against SARS-CoV-2 that are practical for low-resource settings. This study aimed to determine the effectiveness of a relatively inexpensive ultraviolet germicidal irradiation chamber to decontaminate FFRs contaminated with SARS-CoV-2. A custom-designed UVGI chamber was constructed to determine the ability to decontaminate seven FFR models including N95s, KN95, and FFP2s inoculated with SARS-CoV-2. Vflex was excluded due to design folds/pleats and UVGI shadowing inside the chamber. Structural and functional integrity tolerated by each FFR model on repeated decontamination cycles was assessed. Twenty-seven participants were fit-tested over 30 cycles for each model and passed if the fit factor was ≥100. Of the FFR models included for testing, only the KN95 model failed filtration. The 3M™ 3M 1860 and Halyard™ duckbill 46727 (formerly Kimberly Clark) models performed better on fit testing than other models for both pre-and-post decontaminations. Fewer participants (0.3 and 0.7%, respectively) passed fit testing for Makrite 9500 N95 and Greenline 5200 FFP2 and only two for the KN95 model post decontamination. Fit testing appeared to be more affected by donning & doffing, as some passed with adjustment and repeat fit testing. A ≥ 3 log reduction of SARS-CoV-2 was achieved for worn-in FFRs namely Greenline 5200 FFP2. Conclusion: The study showed that not all FFRs tested could withstand 30 cycles of UVGI decontamination without diminishing filtration efficiency or facial fit. In addition, SARS-CoV-2 log reduction varied across the FFRs, implying that the decontamination efficacy largely depends on the decontamination protocol and selection of FFRs. We demonstrated the effectiveness of a low-cost and scalable decontamination method for SARS-CoV-2 and the effect on fit testing using people instead of manikins. It is recognized that extensive experimental evidence for the reuse of decontaminated FFRs is lacking, and thus this study would be relevant and of interest in crisis-capacity settings, particularly in low-resource facilities.

Evaluation of a High-Temperature Pre-Heating System Design for a Large-Scale Additive Manufacturing System.

Additive Manufacturing (AM) of titanium (Ti6Al4V) material using Selective Laser Melting (SLM) may generate significant residual stresses of a tensile nature, which can cause premature component failure. The Aeroswift platform is a large volume AM machine where a high-temperature substrate preheating system is used to mitigate high thermal gradients. The current machine platform is unable to achieve a target build-plate temperature of 600 °C. This study focuses on the analysis of the preheating system design to determine the cause of its inefficiency, and the experimental testing of key components such as the heater and insulation materials. A Finite Element Analysis (FEA) model shows the ceramic heater achieves a maximum temperature of 395 °C, while the substrates (build-plates) only attain 374 °C. Analysis showed that having several metal components in contact and inadequate insulation around the heater caused heat loss, resulting in the preheating system's inefficiency. Additionally, experimental testing shows that the insulation material used was 44% efficient, and a simple insulated test setup was only able to obtain a maximum temperature of 548.8 °C on a 20 mm thick stainless steel 304 plate, which illustrated some of the challenges faced by the current pre-heating design. New design options have been developed and FEA analysis indicates that a reduction in heat loss through improved sub-component configurations can obtain 650 °C degrees above the substrate without changing the heating element power. The development and challenges associated with the large-scale preheating system for AM are discussed, giving an insight into improving its performance.

Parent-in-training: Resident and fellow experiences from pregnancy to parenthood.

BACKGROUND: Residents and fellows with children face distinct challenges; however, knowledge of factors associated with increased parental stress is limited. OBJECTIVE: This study aimed to investigate experiences and concerns of physician trainees and identify factors associated with higher parental stress. METHODS: An anonymous survey was distributed to all resident and fellow trainees in June 2021 to assess experiences regarding parental leave, breastfeeding, and childcare. We used the Parental Stress Scale (PSS) to identify the factors associated with stress and analyzed the results using descriptive statistics, linear regression, and thematic analysis. RESULTS: Of 1719 trainees, 509 participated (62% women, 30% response rate); half were parents. One-third of the respondents (152/470) said that childcare costs affected the number of children they plan to have; One-third of respondents (152/470) said that childcare costs affected the number of children they plan to have; 45% (210/470) said childcare costs affected when they plan to have children. Among parents, the mean PSS score was 44.3 ± 12.3, with no significant gender differences. More women identified as primary or coprimary caregivers (97% [113/117] vs. 79% [60/76], p < .001) and anticipated training extensions due to parental leave (36% vs. 13% men, p = .009). Breastfeeding was associated with significantly higher PSS scores (p = .017). Twenty-four percent of breastfeeding parents (22/93) felt that their program/institution did not support their breastfeeding goals; lack of perceived support was associated with significantly higher PSS scores (63.6 ± 13.1 vs. 38.6 ± 8.7, p < .001). Trainees experiencing unreliable childcare had significantly higher PSS scores (p = .005). Forty percent (64/159) changed their career plans after becoming parents. CONCLUSIONS: Physician trainee parents experience high stress, with women bearing disproportionate burdens in the domains of parental leave and breastfeeding. These results should inform policies promoting trainee wellness and gender equity.

Investigating lane change behaviors and difficulties for senior drivers using naturalistic driving data.

INTRODUCTION: Lane changes can be a complicated maneuver occurring a dynamic environment requiring the integration of many streams of information. Older drivers may struggle with lane changes which may elevate crash risk. METHODS: Real-world lane change behaviors were examined using the Second Strategic Highway Research Program Naturalistic Driving Study database. A total of 393 lane changes were observed for two age groups: middle-aged (30-49), and older (70+) drivers. RESULTS: Older drivers were highly likely to fail to execute an over-the-shoulder glance prior to initiation of a lane change (in 98% of left lane changes and 92% for right lane changes). Older drivers also showed higher rates of OTS glance errors at any point during the lane change in 95% of left lane changes and 86% of right-lane changes. Additionally, older drivers frequently failed to activate the turn signal prior to lane change initiation (60% of lane changes for right changes and 59% for left lane changes). Of the older drivers that made side mirror glances, many occurred after the initiation of the maneuver (46% of left lane changes and 58% of right lane changes) suggesting glances were occurring while changing lanes. CONCLUSIONS: Results for older drivers showed that many key glances (particularly side mirror checks) and turn signal actuations observed in the current study occurred after the initiation of the lane change, ostensibly when this action may be too late to gather relevant information and avoid a conflict. Practical Applications: Knowledge of glance patterns during lane changes for older drivers can help older drivers maintain travel mobility as they age. Either through training to reinforce OTS and side mirror glances, or supplemental devices like convex mirrors or oversized rearview mirrors, older drivers can reduce high-risk lane change maneuvers and help older drivers to maintain their mobility and independence longer.

Unilateral Neuroimaging Findings in Pediatric Craniofacial Scleroderma: Parry-Romberg Syndrome and En Coup de Sabre.

OBJECTIVE: Parry-Romberg syndrome (PRS) and en coup de sabre (ECDS) are subtypes of craniofacial localized scleroderma. Systematic analyses of central nervous system imaging findings and their clinical associations in children are lacking. Here, we aim to characterize neuroimaging findings and associated neurological symptoms in these conditions. METHODS: Neuroimaging and neurological symptoms of children evaluated at our institution with a diagnosis of PRS or ECDS were retrospectively reviewed. Laterality, location, stability, and number of lesion(s) were evaluated, as was the presence of susceptibility lesion(s) and contrast enhancement. History of seizures or headaches was noted. RESULTS: From 2003 to 2019, 80 patients with PRS or ECDS were followed at our institution. Neuroimaging was completed in 73 and found to be abnormal in 25. In 12 (48%) of these 25 cases, headaches and/or seizures were present. In the vast majority of these cases (22/25, 88%), lesions were ipsilateral to skin findings. White matter was involved in 19 (76%) patients. MRI abnormalities preceded a rheumatological diagnosis in 7 (28%). Susceptibility lesions were noted in 11 (44%), and 8 (73%) of these patients endorsed a history of headaches. Most lesions were in the supratentorial compartment, did not enhance, and were stable at 1-year follow up imaging. Of those with progression, susceptibility findings were present at baseline. CONCLUSIONS: Neuroimaging findings in pediatric PRS and ECDS are often supratentorial, stable, unilateral, and ipsilateral to skin findings, and they can precede cutaneous findings.

Linear Scleroderma of the Head - Updates in management of Parry Romberg Syndrome and En coup de sabre: A rapid scoping review across subspecialties.

To provide an update on the current management, including evaluation and treatment, and the available diagnostic tools for linear scleroderma of the head, i.e., Parry-Romberg Syndrome and en coup de sabre (PRS/ECDS). A rapid scoping review of the literature was conducted to include manuscripts published in English between 2010 and 2019. Literature searches were performed in PubMed and EMBASE databases. The were analyzed for descriptive statistic reporting. This study reviewed 215 manuscripts reporting these 1430 patients. Surgical reports comprised the majority of the reviewed literature. Most PRS/ECDS did not appear to receive comprehensive multisubspecialty evaluation for extracutaneous manifestations; 21% of cases noted neurological screening, 4% noted dental screening, and 3% noted ophthalmologic screening. Methotrexate and glucocorticoids remain the most frequent choice for immunosuppressive treatment, though fewer than 7% of patients reported receiving systemic medical therapies. Surgical procedures for cosmetic or functional improvement were common (59%) among the reported patients. Autologous fat grafting was the most frequently utilized cosmetic treatment (50% of procedures) followed by free flap transfers (24% of procedures). There is ongoing need for standardized evaluation, monitoring, and treatment to prevent morbidity in PRS/ECDS, especially in children. When these patients are managed by rheumatologists, methotrexate, and steroids remain the first-line treatment, but a review of the published literature reflects that this may be a minority. Most PRS/ECDS patients are not evaluated in a multidisciplinary fashion. We propose comprehensive evaluations across subspecialties at the baseline and follow-up levels to monitor disease activity and record extracutaneous manifestations, treatment algorithms, and surgical intervention considerations.

Staffs' and managers' perceptions of how and when discrete event simulation modelling can be used as a decision support in quality improvement: a focus group discussion study at two hospital settings in Sweden.

OBJECTIVE: To explore healthcare staffs' and managers' perceptions of how and when discrete event simulation modelling can be used as a decision support in improvement efforts. DESIGN: Two focus group discussions were performed. SETTING: Two settings were included: a rheumatology department and an orthopaedic section both situated in Sweden. PARTICIPANTS: Healthcare staff and managers (n=13) from the two settings. INTERVENTIONS: Two workshops were performed, one at each setting. Workshops were initiated by a short introduction to simulation modelling. Results from the respective simulation model were then presented and discussed in the following focus group discussion. RESULTS: Categories from the content analysis are presented according to the following research questions: how and when simulation modelling can assist healthcare improvement? Regarding how, the participants mentioned that simulation modelling could act as a tool for support and a way to visualise problems, potential solutions and their effects. Regarding when, simulation modelling could be used both locally and by management, as well as a pedagogical tool to develop and test innovative ideas and to involve everyone in the improvement work. CONCLUSIONS: Its potential as an information and communication tool and as an instrument for pedagogic work within healthcare improvement render a broader application and value of simulation modelling than previously reported.

Body ideals for heterosexual romantic partners: gender and sociocultural influences.

In the present study, heterosexual college women (N=327) and men (N=160) were asked about their body type preferences for (hypothetical) romantic partners. Participants chose a particular silhouette value as ideal for a romantic partner, and rated how important it was to them for their partner to have this ideal body type. Men placed more importance on the body silhouette they chose for a partner than women did, and men's importance ratings were positively associated with the rated sexual permissiveness of their peer group and their total media use. Consuming sports media and watching reality television were the best media predictors of men's judgments about women's bodies. Less variability was explained in women's preferences for men partners' bodies, but endorsing adversarial sexual attitudes was positively related to judging the ideals chosen for men's bodies as important. Results were interpreted within both evolutionary and sociocultural theoretical frameworks.

Benefits of a physician-facing tablet presentation of patient symptom data: comparing paper and electronic formats.

BACKGROUND: Providing patient information to physicians in usable form is of high importance. Electronic presentation of patient data may have benefits in efficiency and error rate reduction for these physician facing interfaces. Using a cancer symptom measurement tool (the MD Anderson Symptom Inventory (MDASI)) we assessed the usability of patient data in its raw paper form and compared that to presentation on two electronic presentation formats of different sizes. METHODS: In two separate experiments, undergraduates completed two identical six-part questionnaires on two twenty-patient MDASI data sets. In Experiment 1, participants completed one questionnaire using a paper packet and the other questionnaire using an in-house designed iPad application. In Experiment 2, MDASI data was evaluated using an iPad and iPod Touch. Participants assessed the usability of the devices directly after use. In a third experiment, medical professionals evaluated the paper and iPad interfaces in order to validate the findings from Experiment 1. RESULTS: Participants were faster and more accurate answering questions about patients when using the iPad. The results from the medical professionals were similar. No appreciable accuracy, task time, or usability differences were observed between the iPad and iPod Touch. CONCLUSIONS: Overall, the use of our tablet interface increased the accuracy and speed that users could extract pertinent information from a multiple patient MDASI data set compared to paper. Reducing the size of the interface did not negatively affect accuracy, speed, or usability. Generalization of the results to other physician facing interfaces is discussed.

FcγRIIa requires lipid rafts, but not co-localization into rafts, for effector function.

OBJECTIVE: To determine if receptor localization into lipid rafts, or the lipid rafts themselves, are important for FcγRIIa effector functions. MATERIAL: Wild-type FcγRIIa or mutant FcγRIIa(C208A) that does not translocate to lipid rafts were transfected into Chinese hamster ovary (CHO) cells which have been shown to be reliable cells for studying FcγR function. TREATMENT: Cells were treated with buffer or methyl-ß-cyclodextrin (MßCD) to deplete cholesterol and dissolve the structure of lipid rafts. METHODS: To evaluate lipid raft association, transfected CHO cells were lysed and centrifuged over a sucrose gradient. Fractions were run on SDS-PAGE and blotted for FcγRIIa or sphingolipid GM1 to illustrate the lipid raft fractions. Lateral mobility of GFP-tagged wild-type or mutant FcγRIIa was assessed using fluorescence recovery after photobleaching (FRAP) microscopy. Internalization of IgG-opsonized erythrocytes was assessed by fluorescence microscopy and uptake of heat-aggregated IgG (haIgG) was measured using flow cytometry. RESULTS: We observed that FcγRIIa(C208A) did not localize into lipid rafts. However, the mutant FcγRIIa retained lateral mobility and effector function similar to wild-type FcγRIIa. However, mutant FcγRIIa function was abolished upon treatment with MßCD. CONCLUSIONS: Lipid rafts provide an essential component required for effector activities independent of receptor localization.

Interior point algorithms: guaranteed optimality for fluence map optimization in IMRT.

One of the most widely studied problems of the intensity-modulated radiation therapy (IMRT) treatment planning problem is the fluence map optimization (FMO) problem, the problem of determining the amount of radiation intensity, or fluence, of each beamlet in each beam. For a given set of beams, the fluences of the beamlets can drastically affect the quality of the treatment plan, and thus it is critical to obtain good fluence maps for radiation delivery. Although several approaches have been shown to yield good solutions to the FMO problem, these solutions are not guaranteed to be optimal. This shortcoming can be attributed to either optimization model complexity or properties of the algorithms used to solve the optimization model. We present a convex FMO formulation and an interior point algorithm that yields an optimal treatment plan in seconds, making it a viable option for clinical applications.

Functional optical signal analysis: a software tool for near-infrared spectroscopy data processing incorporating statistical parametric mapping.

Optical topography (OT) relies on the near infrared spectroscopy (NIRS) technique to provide noninvasively a spatial map of functional brain activity. OT has advantages over conventional fMRI in terms of its simple approach to measuring the hemodynamic response, its ability to distinguish between changes in oxy- and deoxy-hemoglobin and the range of human participants that can be readily investigated. We offer a new software tool, functional optical signal analysis (fOSA), for analyzing the spatially resolved optical signals that provides statistical inference capabilities about the distribution of brain activity in space and time and by experimental condition. It does this by mapping the signal into a standard functional neuroimaging analysis software, statistical parametric mapping (SPM), and forms, in effect, a new SPM toolbox specifically designed for NIRS in an OT configuration. The validity of the program has been tested using synthetic data, and its applicability is demonstrated with experimental data.

Seeing or doing? Influence of visual and motor familiarity in action observation.

The human brain contains specialized circuits for observing and understanding actions. Previous studies have not distinguished whether this "mirror system" uses specialized motor representations or general processes of visual inference and knowledge to understand observed actions. We report the first neuroimaging study to distinguish between these alternatives. Purely motoric influences on perception have been shown behaviorally, but their neural bases are unknown. We used fMRI to reveal the neural bases of motor influences on action observation. We controlled for visual and knowledge effects by studying expert dancers. Some ballet moves are performed by only one gender. However, male and female dancers train together and have equal visual familiarity with all moves. Male and female dancers viewed videos of gender-specific male and female ballet moves. We found greater premotor, parietal, and cerebellar activity when dancers viewed moves from their own motor repertoire, compared to opposite-gender moves that they frequently saw but did not perform. Our results show that mirror circuits have a purely motor response over and above visual representations of action. We understand actions not only by visual recognition, but also motorically. In addition, we confirm that the cerebellum is part of the action observation network.

Discrete and analogue quantity processing in the parietal lobe: a functional MRI study.

The human intraparietal sulcus (IPS) is implicated in processing symbolic number information and possibly in nonsymbolic number information. Specific IPS activity for discrete quantities (numerosities) as compared with continuous, analogue quantity has not been demonstrated. Here we use a stimulus-driven paradigm to distinguish automatic estimation of "how many things" from "how much" and "how long." The discrete analogue response task (DART) uses the perception of hues which can change either abruptly (discrete, numerous stimuli) or smoothly (analogue, nonnumerous stimuli) in space or in time. Subjects decide whether they saw more green or more blue. A conjunction analysis of spatial and temporal conditions revealed that bilateral IPS was significantly more active during the processing of discrete stimuli than during analogue stimuli, as was a parietal-occipital transition zone. We suggest that processing numerosity is a distinct process from processing analogue quantity, whether extended in space or time, and that an intraparietal network connects objects' segmentation to the estimation of their numerosity.

Anterior cingulate activity during error and autonomic response.

The contribution of anterior cingulate cortex (ACC) to human cognition remains unclear. The rostral (rACC) and dorsal (dACC) ACC cortex are implicated in tasks that require increased response control due to emotional and cognitive interference, respectively. However, both rACC and dACC are activated by conditions that induce changes in visceral arousal, suggesting that ACC supports a generation of integrated bodily responses. To clarify the relationship between purely cognitive and psychophysiological accounts of ACC function, we scanned 15 subjects using functional magnetic resonance imaging while they performed numerical versions of the Stroop task. To index autonomic arousal, we simultaneously measured pupil diameter. Performance errors accounted for most of the variance in a pupil-derived measure of evoked autonomic arousal. In analysis of the functional imaging data, activity within a region spanning rACC and dACC predicted trial-by-trial variation in autonomic response magnitude and was enhanced during error trials, shown using conjunction analyses. Activity within other loci within rACC predicted evoked autonomic arousal and showed sensitivity to errors but did not meet criteria for both. These data highlight the role of ACC in psychophysiological aspects of error processing and suggest that an interface exists within ACC between cognitive and biobehavioral systems in the service of response adaptation.

Conjunction revisited.

The aim of this note is to revisit the analysis of conjunctions in imaging data. We review some conceptual issues that have emerged from recent discussion (Nichols, T., Brett, M., Andersson, J., Wager, T., Poline, J.-B., 2004. Valid Conjunction Inference with the Minimum Statistic.) and reformulate the conjunction of null hypotheses as a conjunction of k or more effects. Analyses based on minimum statistics have typically used the null hypothesis that k = 0. This enables inferences about one or more effects (k > 0). However, this does not provide control over false-positive rates (FPR) for inferences about a conjunction of k = n effects, over n tests. This is the key point made by Nichols et al., who suggest a procedure based on supremum P values that provides an upper bound on FPR for k = n. Although valid, this is a very conservative procedure, particularly in the context of multiple comparisons. We suggest that an inference on a conjunction of k = n effects is generally unnecessary and distinguish between congruent contrasts that test for the same treatment and incongruent contrasts of the sort used in cognitive conjunctions. For congruent contrasts, the usual inference, k > 0, is sufficient. With incongruent contrasts it is sufficient to infer a conjunction of k >u effects, where u is the number of contrasts that share some uninteresting effect. The issues highlighted by Nichols et al., have important implications for the design and analysis of cognitive conjunction studies and have motivated a change to the SPM software, that affords a test for the more general hypothesis k >u. This more general conjunction test is described.

A heuristic for the degrees of freedom of statistics based on multiple variance parameters.

In neuroimaging, data are often modeled using general linear models. Here, we focus on GLMs with error covariances which are modeled as a linear combination of multiple variance/covariance components. Each of these components is weighted by one variance parameter. In many analyses variance parameters are estimated using restricted maximum likelihood (ReML). Most classical approaches assume the error covariance matrix can be factorized into a single variance parameter and a nonspherical correlation matrix. In this context, the F test based on a single variance parameter, with a suitable correction to the degrees of freedom, is the standard inference tool. This correction can also be adapted to models with multiple variance parameters. However, this extension overlooks the uncertainty about the variance parameter estimates and P values tend to be underestimated. Here, we show how one can overcome this problem to render the F test more exact. This issue is important, because serial correlations in fMRI time series are generally modeled using multiple variance parameters. Another application is to hierarchical linear models, which are used for modeling multisubject data. To illustrate our approach, we apply it to some typical modeling scenarios in fMRI data analysis.