Papers by Catherine Stamoulis
A subspace signal processing approach is proposed for improved scalp EEG-based localization of br... more A subspace signal processing approach is proposed for improved scalp EEG-based localization of broad-focus epileptic seizures, and estimation of the directions of source arrivals (DOA). Ictal scalp EEGs from adult and pediatric patients with broad-focus seizures were first decomposed into dominant signal modes, and signal and noise subspaces at each modal frequency, to improve the signal-to-noise ratio while preserving the original data correlation structure. Transformed (focused) modal signals were then resynthesized into wideband signals from which the number of sources and DOA were estimated. These were compared to denoised signals via principal components analysis (PCA). Coherent subspace processing performed better than PCA, significantly improved the localization of ictal EEGs and the estimation of distinct sources and corresponding DOAs.
BMC Neuroscience, Dec 1, 2015
British Journal of Dermatology, Aug 1, 2019
Spitz naevi are a type of mole (brown skin lump). They are smooth, rounded, pink, red or brown. T... more Spitz naevi are a type of mole (brown skin lump). They are smooth, rounded, pink, red or brown. They contain pigment cells known as spitzoid proliferations. Some spitz naevi look quite worrying, growing rapidly and dark brown in colour, and yet turn out to be benign (harmless) when looked at under the microscope, while others contain atypical (abnormal) or even malignant cells. Even viewing them under a powerful magnifying glass (dermatoscope) does not show whether they are malignant (cancerous); genetic tests provide clues but are not easily available. Consequently it is hard to advise patients, especially children because most of the published data is from adults. So these American doctors reviewed 622 spitzoid proliferations removed at Boston Children's Hospital between 1994 and 2012. Most (82.3%) were benign, 17.2% contained cells that looked worrying (atypical) and 3 (0.5%) turned out to be malignant melanomas. On further investigation they found that patients with malignant lesions were, on average, older (17.2 years) than those with atypical or benign lesions (7.2 and 7.4 years respectively), but tumour type was not linked with skin colour or gender. The 3 melanomas occurred in white people, one on the arm, and the other two on or around the buttocks. Two of the 3 had other tumours but all 3 were alive with no recurrences of skin tumour when last reviewed 4-17 years after diagnosis. Five typical spitz naevi came back as atypical naevi after being partially removed. The authors conclude that it may not be necessary to remove benignlooking spitz naevi in children.
Transient electrophysiological anomalies in the human brain have been associated with neurologica... more Transient electrophysiological anomalies in the human brain have been associated with neurological disorders such as epilepsy, may signal impending adverse events (e.g, seizurse), or may reflect the effects of a stressor, such as insufficient sleep. These, typically brief, high-frequency and heterogeneous signal anomalies remain poorly understood, particularly at long time scales, and their morphology and variability have not been systematically characterized. In continuous neural recordings, their inherent sparsity, short duration and low amplitude makes their detection and classification difficult. In turn, this limits their evaluation as potential biomarkers of abnormal neurodynamic processes (e.g., ictogenesis) and predictors of impending adverse events. A novel algorithm is presented that leverages the inherent sparsity of high-frequency abnormalities in neural signals recorded at the scalp and uses spectral clustering to classify them in very high-dimensional signals spanning several days. It is shown that estimated clusters vary dynamically with time and their distribution changes substantially both as a function of time and space.
2021 43rd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC), Nov 1, 2021
There is growing evidence that seizures are accompanied by multi-system changes, not only in the ... more There is growing evidence that seizures are accompanied by multi-system changes, not only in the brain but also in organs and systems under its control. Non-EEG measurements from these systems could be leveraged to improve seizure prediction, which is difficult but critical to the success of next-generation epilepsy therapies. Clinical electrophysiology studies during presurgical patient evaluations routinely collect continuous EEG but also ECG data that span multiple days. Prior work has reported electrocardiographic changes but has primarily focused on ventricular activity and brief peri-ictal intervals. Using novel data-driven classification and separation of the ECG high-dimensional signal space, this study investigated seizure-related changes in both ventricular and atrial activity. Measures of complexity as well as heart rate and R-R interval length were analyzed over time in continuous ECGs from 22 pediatric patients with pharmacoresistant seizures and no diagnosed cardiovascular anomalies. Fifteen patients (>68%) had significant changes in atrial or ventricular activity (or both) in intervals containing seizures. Thus, for a substantial number of patients, cardiac markers may be specifically modulated by seizures and could be leveraged to improve and personalize seizure prediction.
Bioinformatics, Apr 25, 2012
International Health, Nov 14, 2018
Background: Despite the inclusion of adolescent health in recent global frameworks, limited data ... more Background: Despite the inclusion of adolescent health in recent global frameworks, limited data exist on health indicators in low-income countries. Our objective was to identify socioeconomic measures, risk behaviors and health indicators of young people in Guatemala. Methods: We conducted a secondary data analysis of the Pan American Health Organization's Sistema Informático del Adolescente of 2831 participants ages 10-24 y from 2008 to 2014. We examined frequencies for a core set of items, and generalized regression models assessed correlations between age, sex and ethnicity with health outcomes of interest. Results: Fewer than 17% of participants reported a history of chronic illness (16.6%) and severe psychological problems (16.8%). While 66.1% of participants' mothers and 36.6% of fathers reported job instability, far fewer families had housing instability (1.9% with no electricity, 6.3% with no running water). Fewer than one-third (29.1%) were sexually active and the majority (76.0%) routinely used condoms. About one-quarter (22.6%) reported abnormal mood. Indigenous participants were significantly more likely to have experienced psychological problems (odds ratio [OR] 1.75 [confidence interval {CI} 1.65-1.86]) and violence (OR 1.34 [CI 1.27-1.42]) compared with whites. Conclusions: The prevalence of risk behaviors and mental health concerns is low compared with other sources of national and regional data. Further work is needed to examine the benefits and limitations of this system in order to improve health surveillance.
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineer... more Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1997.Includes bibliographical references (leaves 244-247).by Catherine Stamoulis.Ph.D
Journal of Computational Neuroscience, Feb 4, 2010
Local field potentials (LFPs) measure aggregate neural activity resulting from the coordinated fi... more Local field potentials (LFPs) measure aggregate neural activity resulting from the coordinated firing of neurons within a local network. We hypothesized that state parameters associated with the underlying brain dynamics may be encoded in LFPs but may not be directly measurable in the signal temporal and spectral contents. Using the Kalman filter we estimated latent state changes in LFPs recorded in monkey motor cortical areas during the execution of a visually instructed reaching task, under different applied force conditions. Prior to the estimation, matched filtering was performed to decouple behavior-relevant signals [24] from unrelated background oscillations. State changes associated with baseline oscillations appeared insignificant. In contrast, state changes estimated from LFP components associated with the execution of movement were significant. Approximately direction-invariant state vectors were consistently observed. Their patterns appeared invariant also to force field conditions, with a peak in the first 200 ms of the movement interval, but exponentially decreasing to the zero state approximately 200 ms from movement onset, also the time at which movement velocity reached its peak. Thus, state appeared to be modulated by the dynamics of movement but neither by movement direction nor by the mechanical environment. Finally, we compared state vectors estimated using the Kalman filter to the basis functions obtained through This work was supported in part by NIH grants 5T32NS048005-05 and 1UL1RR025758-01 (CS) and NS-044393 (AR)
Journal of Bisexuality, Jan 2, 2019
This study examined associations between sexual fluidity in attractions and related beliefs and a... more This study examined associations between sexual fluidity in attractions and related beliefs and attitudes among sexual minority and heterosexual young adults. Two college and community-based samples who completed an online survey were combined to yield 421 young adults (224 women, 188 men, 7 transgender, and 2 another gender), ages 18-26 years. Two hypothesized models were tested, one with sexual fluidity in attractions as the outcome of related beliefs and attitudes, and one with sexual fluidity in attractions as the predictor of related beliefs and attitudes. Results indicated that sexuality origin beliefs significantly predicted entity/incremental (E/I) views of sexual orientation among sexual minority women and men and heterosexual men, but not sexual fluidity in attractions among any of the groups. E/I views of sexual orientation predicted sexual fluidity in attractions for heterosexual women and men but in the opposite direction from what was hypothesized. Attitudes toward bisexuality significantly predicted sexual fluidity in attractions for sexual minority women only. Sexual fluidity in attractions significantly predicted E/I views of sexual orientation and attitudes toward bisexuality but only among sexual minority women. This study highlights the complexity of sexual fluidity and related beliefs and attitudes among sexual minority and heterosexual individuals.
American Journal of Human Biology, Aug 26, 2016
ObjectivesModern reference standards for long bone growth are lacking for infants (≤1 year). This... more ObjectivesModern reference standards for long bone growth are lacking for infants (≤1 year). This study develops a quantitative framework to characterize lower extremity bone shaft growth during infancy based on radiographic images, and compares it to data from the 1930s.MethodsFemoral, tibial, and fibular shaft length measurements (diaphysis plus metaphysis) were collected retrospectively from 70 infants on initial and follow‐up skeletal surveys performed for suspected abuse (7/2005—2/2013). These serial skeletal survey data (SSSD) were compared to the Denver Child Research Council data (DCRCD), a 1930's longitudinal dataset from 80 infants. Mixed effects regression models were developed to estimate growth trajectories from these data. Growth trajectories and short‐term (≤2 months) growth rates were compared.ResultsStatistically distinct models described the contemporary (SSSD) and historic (DCRCD) datasets; however, there was substantial overlap (77—90%) between their confidence bands for the three measured bones. Based on developed models, the average long bone shafts of the DCRCD are shorter at birth than SSSD (femur: 77.0 vs. 82.3 mm; tibia: 64.4 vs. 68.2 mm; fibula: 61.0 vs. 64.4 mm), but the DCRCD long bone growth rates are faster than SSSD (femur: 0.21 vs. 0.17 mm/day; tibia: 0.16 vs. 0.14 mm/day; fibula: 0.15 vs. 0.14 mm/day). Short‐term growth rates of these bones decreased with age. The effect of sexual dimorphism on long bone growth during infancy was non‐significant.ConclusionThis study provides reference standards for long bone growth rates during the dynamic period of infancy that may aid clinical assessment, and also inform research studies of disorders associated with altered skeletal growth.
Baseline neurodynamics are believed to play an important role in normal brain function. A potenti... more Baseline neurodynamics are believed to play an important role in normal brain function. A potentially intrinsic property of the brain is the weak coupling between networks at rest, which enables it to be flexible, adapt, process novel stimuli, and learn. Brain regions become differentially coordinated in response to cognitive task and behavior demands and external stimuli. However, abnormally synchronized resting brain networks may also be associated with different pathologies. We investigated baseline network dynamics in the epileptic brain using information theoretic parameters to quantify coupling and directionality of information flow between different cortical regions. We estimated relative entropy, conditional mutual information and a related measure of directional coupling, from EEGs of patients with epilepsy and healthy subjects. At rest, the healthy brain appears to be characterized by low and non-directional network coupling, whereas the epileptic brain appears to be transiently and directionally synchronized.
Academic Pediatrics, Mar 1, 2018
International Journal of Obesity
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineerin... more Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1994.Includes bibliographical references (leaves 167-175).by Catherine Stamoulis.M.S
Infection and Immunity, 2021
A comprehensive understanding of how Staphylococcus aureus adapts to cause infections in humans c... more A comprehensive understanding of how Staphylococcus aureus adapts to cause infections in humans can inform development of diagnostic, therapeutic, and preventive approaches. Expression analysis of clinical strain libraries depicts in vitro conditions that differ from those in human infection, but low bacterial burden and the requirement for reverse transcription or nucleic acid amplification complicate such analyses of bacteria causing human infection.
Journal of Adolescent Health, 2020
Circulation, 2019
Introduction: The American Heart Association (AHA) Go Red for Women campaign has substantially im... more Introduction: The American Heart Association (AHA) Go Red for Women campaign has substantially improved heart disease awareness among adult women. Little is known about how younger women in adolescence and young adulthood (AYA) perceive their risk of heart disease during this key time in the life course for primordial prevention. Methods: We used an explanatory sequential mixed method design consisting of the AHA National Women’s Health Study survey and follow-up focus groups. We surveyed a random convenience sample of 331 AYA women ages 15-24 years presenting for care at an urban academic medical center and a community health center. Survey results guided development of a qualitative guide used during eight online, semi-structured focus groups with 32 young women. We report descriptive statistics performed using Matlab (Mathworks, Inc.) and thematic analyses conducted to synthesize data from the online focus groups using NVivo 11. Results: Only 10% [n=33] of AYA identified heart di...
BMJ open, Jan 5, 2018
To assess the diagnostic accuracy of thermal imaging (TI) in the setting of focal consolidative p... more To assess the diagnostic accuracy of thermal imaging (TI) in the setting of focal consolidative pneumonia with chest X-ray (CXR) as the gold standard. A large, 973-bed teaching hospital in Boston, Massachusetts. 47 patients enrolled, 15 in a training set, 32 in a test set. Age range 10 months to 82 years (median=50 years). Subjects received CXR with subsequent TI within 4 hours of each other. CXR and TI were assessed in blinded random order. Presence of focal opacity (pneumonia) on CXR, the outcome parameter, was recorded. For TI, presence of area(s) of increased heat (pneumonia) was recorded. Fisher's exact test was used to assess the significance of the correlations of positive findings in the same anatomical region. With TI compared with the CXR (the outcome parameter), sensitivity was 80.0% (95% CIs 29.9% to 98.9%), specificity was 57.7% (95% CI 37.2% to 76.0%). Positive predictive value of TI was 26.7% (95% CI 8.9% to55.2%) and its negative predictive value was 93.8% (95% C...
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Papers by Catherine Stamoulis