Retrospective analysis of neurological findings in esophageal atresia: Allostatic load of disease complexity, cumulative sedation, and anesthesia exposure.

BACKGROUND: There is limited knowledge regarding the impact of perioperative critical care on frequency of neurological imaging findings following esophageal atresia (EA) repair. METHODS: This is a retrospective study of infants (n = 70) following EA repair at a single institution (2009-2020). Sex, gestational age at birth, type of surgical repair, underlying disease severity, and frequency of neurologic imaging findings were obtained. We quantified the length of postoperative pain/sedation treatment and anesthesia exposure in the first year of life. Data were presented as numerical sums and percentages, while associations were measured using Spearman's Rho. RESULTS: Vertebral/spinal cord imaging was performed in all infants revealing abnormalities in 44% (31/70). Cranial/brain imaging findings were identified in 67% (22/33) of infants in the context of clinically indicated imaging (47%; 33/70). Long-gap EA patients (n = 16) received 10 times longer postoperative pain/sedation treatment and twice the anesthesia exposure compared with short-gap EA patients (n = 54). The frequency of neurologic imaging findings did not correlate with underlying disease severity scores, length of pain/sedation treatment, or cumulative anesthesia exposure. Lack of associations between clinical measures and imaging findings should be interpreted with caution given possible underestimation of cranial/brain findings. CONCLUSIONS: We propose that all infants with EA undergo brain imaging in addition to routine spinal imaging given the high burden of abnormal brain/cranial findings in our cohort. Quantification of pain/sedation and anesthesia exposure in long-gap EA patients could be used as indirect markers in future studies assessing the risk of neurological sequelae as evidenced by early abnormalities on brain imaging.

Acute Dystonic Reaction After Propofol Administration: A Pediatric Case Report.

We present a case of a 12-year-old female with a history of infantile spasms who developed a propofol-associated acute dystonic reaction after emergence from general anesthesia for foot surgery. Uniquely, the patient's postoperative symptoms of an acute dystonic reaction were refractory to standard treatment with anticholinergics but were successfully treated with corticosteroids. The absence of any dystonic symptoms following subsequent foot surgery under general anesthesia without propofol supported a propofol-associated etiology. This case may contribute to a better understanding of the underlying mechanisms of propofol-associated acute dystonic reactions and adds a possible new treatment option.

Infant Perioperative Risk Factors and Adverse Brain Findings Following Long-Gap Esophageal Atresia Repair.

Recent findings implicate brain vulnerability following long-gap esophageal atresia (LGEA) repair. We explored the relationship between easily quantifiable clinical measures and previously reported brain findings in a pilot cohort of infants following LGEA repair. MRI measures (number of qualitative brain findings; normalized brain and corpus callosum volumes) were previously reported in term-born and early-to-late premature infants (n = 13/group) <1 year following LGEA repair with the Foker process. The severity of underlying disease was classified by an (1) American Society of Anesthesiologist (ASA) physical status and (2) Pediatric Risk Assessment (PRAm) scores. Additional clinical end-point measures included: anesthesia exposure (number of events; cumulative minimal alveolar concentration (MAC) exposure in hours), length (in days) of postoperative intubated sedation, paralysis, antibiotic, steroid, and total parenteral nutrition (TPN) treatment. Associations between clinical end-point measures and brain MRI data were tested using Spearman rho and multivariable linear regression. Premature infants were more critically ill per ASA scores, which showed a positive association with the number of cranial MRI findings. Clinical end-point measures together significantly predicted the number of cranial MRI findings for both term-born and premature infant groups, but none of the individual clinical measures did on their own. Listed easily quantifiable clinical end-point measures could be used together as indirect markers in assessing the risk of brain abnormalities following LGEA repair.

Body size and brain volumetry in the rat following prolonged morphine administration in infancy and adulthood.

Background: Prolonged morphine treatment in infancy is associated with a high incidence of opioid tolerance and dependence, but our knowledge of the long-term consequences of this treatment is sparse. Using a rodent model, we examined the (1) short- and (2) long-term effects of prolonged morphine administration in infancy on body weight and brain volume, and (3) we evaluated if subsequent dosing in adulthood poses an increased brain vulnerability. Methods: Newborn rats received subcutaneous injections of either morphine or equal volume of saline twice daily for the first two weeks of life. In adulthood, animals received an additional two weeks of saline or morphine injections before undergoing structural brain MRI. After completion of treatment, structural T2-weigthed MRI images were acquired on a 7 T preclinical scanner (Bruker) using a RARE FSE sequence. Total and regional brain volumes were manually extracted from the MRI images using ITK-SNAP (v.3.6). Regions of interest included the brainstem, the cerebellum, as well as the forebrain and its components: the cerebral cortex, hippocampus, and deep gray matter (including basal ganglia, thalamus, hypothalamus, ventral tegmental area). Absolute (cm3) and normalized (as % total brain volume) values were compared using a one-way ANOVA with Tukey HSD post-hoc test. Results: Prolonged morphine administration in infancy was associated with lower body weight and globally smaller brain volumes, which was not different between the sexes. In adulthood, females had lower body weights than males, but no difference was observed in brain volumes between treatment groups. Our results are suggestive of no long-term effect of prolonged morphine treatment in infancy with respect to body weight and brain size in either sex. Interestingly, prolonged morphine administration in adulthood was associated with smaller brain volumes that differed by sex only in case of previous exposure to morphine in infancy. Specifically, we report significantly smaller total brain volume of female rats on account of decreased volumes of forebrain and cortex. Conclusions: Our study provides insight into the short- and long-term consequences of prolonged morphine administration in an infant rat model and suggests brain vulnerability to subsequent exposure in adulthood that might differ with sex.

Impact of Infant Thoracic Non-cardiac Perioperative Critical Care on Homotopic-Like Corpus Callosum and Forebrain Sub-regional Volumes.

Previously, we reported quantitatively smaller total corpus callosum (CC) and total forebrain size in critically ill term-born and premature patients following complex perioperative critical care for long-gap esophageal atresia (LGEA) that included Foker process repair. We extended our cross-sectional pilot study to determine sub-regional volumes of CC and forebrain using structural brain MRI. Our objective was to evaluate region-specific CC as an in-vivo marker for decreased myelination and/or cortical neural loss of homotopic-like sub-regions of the forebrain. Term-born (n = 13) and premature (n = 13) patients, and healthy naïve controls (n = 21) <1-year corrected age underwent non-sedated MRI using a 3T Siemens scanner, as per IRB approval at Boston Children's Hospital following completion of clinical treatment for Foker process. We used ITK-SNAP (v.3.6) to manually segment six sub-regions of CC and eight sub-regions of forebrain as per previously reported methodology. Group differences were assessed using a general linear model univariate analysis with corrected age at scan as a covariate. Our analysis implicates globally smaller CC and forebrain with sub-region II (viz. rostral body of CC known to connect to pre-motor cortex) to be least affected in comparison to other CC sub-regions in LGEA patients. Our report of smaller subgenual forebrain implicates (mal)adaptation in limbic circuits development in selected group of infant patients following LGEA repair. Future studies should include diffusion tractography studies of CC in further evaluation of what appears to represent global decrease in homotopic-like CC/forebrain size following complex perioperative critical care of infants born with LGEA.

From the Ground Up: Esophageal Atresia Types, Disease Severity Stratification and Survival Rates at a Single Institution.

Esophageal atresia (EA), although a rare congenital anomaly, represents one of the most common gastrointestinal birth defects. There is a gap in our knowledge regarding the impact of perioperative critical care in infants born with EA. This study addresses EA types, disease severity stratification, and mortality in a retrospective cohort at a single institution. Institutional Review Board approved our retrospective cross-sectional study of term-born (n = 53) and premature infants (28-37 weeks of gestation; n = 31) that underwent primary surgical repair of EA at a single institution from 2009-2020. Demographic and clinical data were obtained from the electronic medical record, Powerchart (Cerner, London, UK). Patients were categorized by (i) sex, (ii) gestational age at birth, (iii) types of EA (in relation to respiratory tract anomalies), (iv) co-occurring congenital anomalies, (v) severity of disease (viz. American Society of Anesthesiologists (ASA) and Pediatric Risk Assessment (PRAm) scores), (vi) type of surgical repair for EA (primary anastomosis vs. Foker process), and (vii) survival rate classification using Spitz and Waterston scores. Data were presented as numerical sums and percentages. The frequency of anatomical types of EA in our cohort parallels that of the literature: 9.5% (8/84) type A, 9.5% (8/84) type B, 80% (67/84) type C, and 1% (1/84) type D. Long-gap EA accounts for 88% (7/8) type A, 75% (6/8) type B, and 13% (9/67) type C in the cohort studied. Our novel results show a nearly equal distribution of sex per each EA type, and gestational age (term-born vs. premature) by anatomical EA type. PRAm scoring showed a wider range of disease severity (3-9) than ASA scores (III and IV). The survival rate in our EA cohort dramatically increased in comparison to the literature in previous decades. This retrospective analysis at a single institution shows incidence of EA per sex and gestational status for anatomical types (EA type A-D) and by surgical approach (primary anastomosis vs. Foker process for short-gap vs. long-gap EA, respectively). Despite its wider range, PRAm score was not more useful in predicting disease severity in comparison to ASA score. Increased survival rates over the last decade suggest a potential need to assess unique operative and perioperative risks in this unique population of patients. Presented findings also represent a foundation for future clinical studies of outcomes in infants born with EA.

Head circumference in infants undergoing Foker process for long-gap esophageal atresia repair: Call for attention.

INTRODUCTION: We extended our pilot study in infants following long-gap esophageal atresia (LGEA) repair to report head circumference, an easily obtainable indirect measure of brain size. Data are presented in the context of previously reported body weight and T2-weighted MRI measures of intracranial and brain volumes. METHODS: Clinical information and head circumference were obtained for term-born (n = 13) and premature (n = 13) infants following LGEA repair with Foker process, as well as healthy term-born controls (n = 20) <1-year corrected age who underwent non-sedated research MRI. General Linear Model univariate analysis with corrected age at scan as a covariate and Bonferroni adjusted p values assessed group differences. RESULTS: We report no difference in head circumference between the three groups. Such findings paralleled trends in body weight and total intracranial volume but not in brain volume as previously reported for the same pilot cohort. DISCUSSION: Results suggest uncompromised somatic and head growth after repair of LGEA. In contrast, a novel finding of discrepancy between head circumference (novel data) and brain size (previously published data) in the same cohort suggests that head circumference might not be the best indirect measure of brain size in selected group of patients.

Infant study of hemispheric asymmetry after long-gap esophageal atresia repair.

OBJECTIVES: Previous studies have demonstrated that infants are typically born with a left-greater-than-right forebrain asymmetry that reverses throughout the first year of life. We hypothesized that critically ill term-born and premature patients following surgical and critical care for long-gap esophageal atresia (LGEA) would exhibit alteration in expected forebrain asymmetry. METHODS: Term-born (n = 13) and premature (n = 13) patients, and term-born controls (n = 23) <1 year corrected age underwent non-sedated research MRI following completion of LGEA treatment via Foker process. Structural T1- and T2-weighted images were collected, and ITK-SNAP was used for forebrain tissue segmentation and volume acquisition. Data were presented as absolute (cm3 ) and normalized (% total forebrain) volumes of the hemispheres. All measures were checked for normality, and group status was assessed using a general linear model with age at scan as a covariate. RESULTS: Absolute volumes of both forebrain hemispheres were smaller in term-born and premature patients in comparison to controls (p < 0.001). Normalized hemispheric volume group differences were detected by T1-weighted analysis, with premature patients demonstrating right-greater-than-left hemisphere volumes in comparison to term-born patients and controls (p < 0.01). While normalized group differences were very subtle (a right hemispheric predominance of roughly 2% of forebrain volume), they represent a deviation from the expected pattern of hemispheric brain asymmetry. INTERPRETATION: Our pilot quantitative MRI study of hemispheric volumes suggests that premature patients might be at risk of altered expected left-greater-than-right forebrain asymmetry following repair of LGEA. Future neurobehavioral studies in infants born with LGEA are needed to elucidate the functional significance of presented anatomical findings.

Ketamine activates cell cycle signaling and apoptosis in the neonatal rat brain.

BACKGROUND: Prolonged exposure to ketamine results in accelerated neurodegeneration and neurocognitive deficits in the neonatal rats. Experimental models of neurodegeneration have implicated reentry of postmitotic neurons into the cell cycle, leading to cell death. The authors hypothesize that the ketamine-induced neuroapoptosis is partially due to aberrant cycle cell reentry. To explore this hypothesis, the authors characterized the effect of ketamine on the cell cycle signaling pathway in the developing rodent brain in vivo and in vitro. METHODS: Postnatal day 7 rat pups and primary neurons were used for the experiments. Each rat pup received five intraperitoneal doses of either saline or ketamine (5, 10, and 20 mg/kg/dose) at 90-min intervals over 6 h. Primary neurons were exposed to varying concentrations of ketamine to determine the dose and duration effects. The expression of cell cycle proteins (cyclin D1, cyclin-dependent kinase 4, and E2F1), Bcl2-interacting mediator of cell death (Bim), and activated caspase-3 was determined. The effect of cyclin D1 knockdown by small interfering RNA was also examined in primary neurons incubated in ketamine. RESULTS: Ketamine mediated a dose- and time-dependent increase in expression of cell cycle proteins and activated caspase-3. Cyclin D1, cyclin-dependent kinase 4, E2F1, Bim, and cleaved caspase-3 expression increased at 12 h and peaked at 24 h in vitro. Knockdown of cyclin D1 by small interfering RNA attenuated Bim and cleaved caspase-3 expression. CONCLUSION: These findings support a model in which ketamine induces aberrant cell cycle reentry, leading to apoptotic cell death in the developing rat brain.

Infant Corpus Callosum Size After Surgery and Critical Care for Long-Gap Esophageal Atresia: Qualitative and Quantitative MRI.

Previous studies in preterm infants report white matter abnormalities of the corpus callosum (CC) as an important predictor of neurodevelopmental outcomes. Our cross-sectional study aimed to describe qualitative and quantitative CC size in critically ill infants following surgical and critical care for long-gap esophageal atresia (LGEA) - in comparison to healthy infants - using MRI. Non-sedated brain MRI was acquired for full-term (n = 13) and premature (n = 13) patients following treatment for LGEA, and controls (n = 20) <1 year corrected age. A neuroradiologist performed qualitative evaluation of T1-weighted images. ITK-SNAP was used for linear, 2-D and 3-D manual CC measures and segmentations as part of CC size quantification. Qualitative MRI analysis indicated underdeveloped CC in both patient groups in comparison to controls. We show no group differences in mid-sagittal CC length. Although 2-D results were inconclusive, volumetric analysis showed smaller absolute (F(2,42) = 20.40, p < 0.001) and normalized (F(2,42) = 16.61, p < 0.001) CC volumes following complex perioperative treatment for LGEA in both full-term and premature patients, suggesting delayed or diminished CC growth in comparison to controls, with no difference between patient groups. Future research should look into etiology of described differences, neurodevelopmental outcomes, and role of the CC as an early marker of neurodevelopment in this unique infant population.

Evaluation of Postnatal Sedation in Full-Term Infants.

Prolonged sedation in infants leads to a high incidence of physical dependence. We inquired: (1) "How long does it take to develop physical dependence to sedation in previously naïve full-term infants without known history of neurologic impairment?" and (2) "What is the relationship between length of sedation to length of weaning and hospital stay?". The retrospective study included full-term patients over a period of one year that were <1 year of age and received opioids and benzodiazepines >72 hours. Quantification of fentanyl, morphine, and midazolam were compared among three time periods: <5 days, 5-30 days, and >30 days using t-test or one-way analysis of variance. Identified full-term infants were categorized into surgical (14/44) or medical (10/44) groups, while those with neurological involvement (20/44) were excluded. Physical dependence in full-term infants occurred following sedation ≥5 days. Infants with surgical disease received escalating doses of morphine and midazolam when administered >30 days. A positive association between length of sedation and weaning period was found for both respiratory (p < 0.01) and surgical disease (p = 0.012) groups, while length of sedation is related to hospital stay for the respiratory (p < 0.01) but not the surgical disease group (p = 0.1). Future pharmacological directions should lead to standardized sedation protocols and evaluate patient neurocognitive outcomes.

Neonatal functional brain maturation in the context of perioperative critical care and pain management: A case report.

INTRODUCTION: Remarkable plasticity during the first year of life imparts heighted vulnerability of the developing infant brain. Application of resting-state functional magnetic resonance imaging (rs-fMRI) in infants may contribute to our understanding of neuroplastic changes associated with therapeutic interventions and/or brain insults. In addition to showing clinically relevant incidental brain MRI findings, the objective of our pilot study was to test feasibility of rs-fMRI methods at this early age in the context of pediatric perioperative critical care. METHODS: We report the case of a former 33-week premature infant born with long-gap esophageal atresia that underwent complex perioperative critical care (Foker process) requiring prolonged post-operative sedation and whom presented with incidental subdural hematoma. Rs-fMRI data was acquired before (at 1-month corrected age) and after (at 2.25-months corrected age) complex perioperative care. We evaluated resting-state functional connectivity (RSFC) using graph theory to explore the complex structure of brain networks. RESULTS: A transient increase in head circumference coincided temporally with lifting of sedation and initiation of sedation drugs weaning, and qualified for hydrocephalus (93%) but not macrocephaly (>95%). RSFC analysis identified networks spatially consistent with those previously described in the literature, with notable pre-post-treatment qualitative differences in correlated and anticorrelated spontaneous brain activity. DISCUSSION: Current definitions of macrocephaly may require lower threshold criteria for monitoring of critically ill infants. Although we demonstrate that available rs-fMRI could be effectively applied in a critically ill infant in the setting of brain pathology, future group-level studies should investigate RSFC to evaluate maintenance of network homeostasis during development of both healthy and critically ill infants.

Quantitative MRI study of infant regional brain size following surgery for long-gap esophageal atresia requiring prolonged critical care.

INTRODUCTION: Little is known regarding the impact of concurrent critical illness and thoracic noncardiac perioperative critical care on postnatal brain development. Previously, we reported smaller total brain volumes in both critically ill full-term and premature patients following complex perioperative critical care for long-gap esophageal atresia (LGEA). Our current report assessed trends in regional brain sizes during infancy, and probed for any group differences. METHODS: Full-term (n = 13) and preterm (n = 13) patients without any previously known neurological concerns, and control infants (n = 16), underwent non-sedated 3 T MRI in infancy (<1 year old). T2-weighted images underwent semi-automated brain segmentation using Morphologically Adaptive Neonatal Tissue Segmentation (MANTiS). Regional tissue volumes of the forebrain, deep gray matter (DGM), cerebellum, and brainstem are presented as absolute (cm3) and normalized (% total brain volume (%TBV)) values. Group differences were assessed using a general linear model univariate analysis with corrected age at scan as a covariate. RESULTS: Absolute volumes of regions analyzed increased with advancing age, paralleling total brain size, but were significantly smaller in both full-term and premature patients compared to controls. Normalized volumes (%TBV) of forebrain, DGM, and cerebellum were not different between subject groups analyzed. Normalized brainstem volumes showed group differences that warrant future studies to confirm the same finding. DISCUSSION: Both full-term and premature critically ill infants undergoing life-saving surgery for LGEA are at risk of smaller total and regional brain sizes. Normalized volumes support globally delayed or diminished brain growth in patients. Future research should look into neurodevelopmental outcomes of infants born with LGEA.

Infant Brain Structural MRI Analysis in the Context of Thoracic Non-cardiac Surgery and Critical Care.

Objective: To determine brain magnetic resonance imaging (MRI) measures of cerebrospinal fluid (CSF) and whole brain volume of full-term and premature infants following surgical treatment for thoracic non-cardiac congenital anomalies requiring critical care. Methods: Full-term (n = 13) and pre-term (n = 13) patients with long-gap esophageal atresia, and full-term naïve controls (n = 19) < 1 year corrected age, underwent non-sedated brain MRI following completion of thoracic non-cardiac surgery and critical care treatment. Qualitative MRI findings were reviewed and reported by a pediatric neuroradiologist and neurologist. Several linear brain metrics were measured using structural T1-weighted images, while T2-weighted images were required for segmentation of total CSF and whole brain tissue using the Morphologically Adaptive Neonatal Tissue Segmentation (MANTiS) tool. Group differences in absolute (mm, cm3) and normalized (%) data were analyzed using a univariate general linear model with age at scan as a covariate. Mean normalized values were assessed using one-way ANOVA. Results: Qualitative brain findings suggest brain atrophy in both full-term and pre-term patients. Both linear and volumetric MRI analyses confirmed significantly greater total CSF and extra-axial space, and decreased whole brain size in both full-term and pre-term patients compared to naïve controls. Although linear analysis suggests greater ventricular volumes in all patients, volumetric analysis showed that normalized ventricular volumes were higher only in premature patients compared to controls. Discussion: Linear brain metrics paralleled volumetric MRI analysis of total CSF and extra-axial space, but not ventricular size. Full-term infants appear to demonstrate similar brain vulnerability in the context of life-saving thoracic non-cardiac surgery requiring critical care as premature infants.

Neurologic Injury and Brain Growth in the Setting of Long-Gap Esophageal Atresia Perioperative Critical Care: A Pilot Study.

We previously showed that infants born with long-gap esophageal atresia (LGEA) demonstrate clinically significant brain MRI findings following repair with the Foker process. The current pilot study sought to identify any pre-existing (PRE-Foker process) signs of brain injury and to characterize brain and corpus callosum (CC) growth. Preterm and full-term infants (n = 3/group) underwent non-sedated brain MRI twice: before (PRE-Foker scan) and after (POST-Foker scan) completion of perioperative care. A neuroradiologist reported on qualitative brain findings. The research team quantified intracranial space, brain, cerebrospinal fluid (CSF), and CC volumes. We report novel qualitative brain findings in preterm and full-term infants born with LGEA before undergoing Foker process. Patients had a unique hospital course, as assessed by secondary clinical end-point measures. Despite increased total body weight and absolute intracranial and brain volumes (cm3) between scans, normalized brain volume was decreased in 5/6 patients, implying delayed brain growth. This was accompanied by both an absolute and relative CSF volume increase. In addition to qualitative findings of CC abnormalities in 3/6 infants, normative CC size (% brain volume) was consistently smaller in all infants, suggesting delayed or abnormal CC maturation. A future larger study group is warranted to determine the impact on the neurodevelopmental outcomes of infants born with LGEA.

Preoperative Evaluation of the Pediatric Patient.

The article reviews frequently encountered preoperative concerns with a goal of minimizing complications during administration of pediatric anesthesia. It is written with general anesthesiologists in mind and provides a helpful overview of concerns for pediatric patient preparation for routine and nonemergent procedures or interventions. It covers unique topics for the pediatric population, including gestational age, respiratory and cardiovascular concerns, fasting guidelines, and management of preoperative anxiety, as well as the current hot topic of the potential neurotoxic effects of anesthetics on the developing brain.

Astrocytic hypertrophy in the rat ventral tegmental area following chronic morphine differs with age.

The ventral tegmental area (VTA) is the origin of the mesolimbic dopaminergic system known to play an integral role in mediating reward and development of drug addiction. Although the differences in neuronal plasticity of VTA at various ages remain to be understood, age is known to influence the effects of chronic opioids. In addition, adaptations associated with exposure to opioids within glial populations located in the VTA are poorly understood. The objective of the study was to determine if there are changes in astrocytic immunofluorescent labeling in the VTA following chronic morphine administration in a rat model at different ages: newborn at postnatal day (PD)7 and adult (estimated PD57). We hypothesized that increased immunohistochemical labeling of an astrocytic marker, glial fibrillary acidic protein (GFAP) in the VTA following chronic administration of morphine will not differ with age. Two groups of rats were analyzed: chronic morphine and saline control treatment groups. Either morphine (10 mg/kg) or equal volume of saline was given subcutaneously twice daily for 6½ days. On the 7th day of treatment, animals were anesthetized and perfused at one hour after the final drug injection. Coronal sections of the midbrain were processed for immunofluorescent identification of GFAP that was noted at both ages. We report an increase in both (1) GFAP labeling intensity, as well as (2) the percent area occupied by astrocytes that are immunoreactive for GFAP following chronic morphine when compared to saline treatment in the VTA only for the adults (n=6/group) but not infant rats at PD7 (n=5/group). Our findings suggest that adaptations in the mesolimbic dopaminergic system produced by repeated exposure to opioids may be associated with changes in glial function that differ with age.

Resting-State Functional Connectivity in the Infant Brain: Methods, Pitfalls, and Potentiality.

Early brain development is characterized by rapid growth and perpetual reconfiguration, driven by a dynamic milieu of heterogeneous processes. Postnatal brain plasticity is associated with increased vulnerability to environmental stimuli. However, little is known regarding the ontogeny and temporal manifestations of inter- and intra-regional functional connectivity that comprise functional brain networks. Resting-state functional magnetic resonance imaging (rs-fMRI) has emerged as a promising non-invasive neuroinvestigative tool, measuring spontaneous fluctuations in blood oxygen level dependent (BOLD) signal at rest that reflect baseline neuronal activity. Over the past decade, its application has expanded to infant populations providing unprecedented insight into functional organization of the developing brain, as well as early biomarkers of abnormal states. However, many methodological issues of rs-fMRI analysis need to be resolved prior to standardization of the technique to infant populations. As a primary goal, this methodological manuscript will (1) present a robust methodological protocol to extract and assess resting-state networks in early infancy using independent component analysis (ICA), such that investigators without previous knowledge in the field can implement the analysis and reliably obtain viable results consistent with previous literature; (2) review the current methodological challenges and ethical considerations associated with emerging field of infant rs-fMRI analysis; and (3) discuss the significance of rs-fMRI application in infants for future investigations of neurodevelopment in the context of early life stressors and pathological processes. The overarching goal is to catalyze efforts toward development of robust, infant-specific acquisition, and preprocessing pipelines, as well as promote greater transparency by researchers regarding methods used.

Identifying Rodent Resting-State Brain Networks with Independent Component Analysis.

Rodent models have opened the door to a better understanding of the neurobiology of brain disorders and increased our ability to evaluate novel treatments. Resting-state functional magnetic resonance imaging (rs-fMRI) allows for in vivo exploration of large-scale brain networks with high spatial resolution. Its application in rodents affords researchers a powerful translational tool to directly assess/explore the effects of various pharmacological, lesion, and/or disease states on known neural circuits within highly controlled settings. Integration of animal and human research at the molecular-, systems-, and behavioral-levels using diverse neuroimaging techniques empowers more robust interrogations of abnormal/ pathological processes, critical for evolving our understanding of neuroscience. We present a comprehensive protocol to evaluate resting-state brain networks using Independent Component Analysis (ICA) in rodent model. Specifically, we begin with a brief review of the physiological basis for rs-fMRI technique and overview of rs-fMRI studies in rodents to date, following which we provide a robust step-by-step approach for rs-fMRI investigation including data collection, computational preprocessing, and brain network analysis. Pipelines are interwoven with underlying theory behind each step and summarized methodological considerations, such as alternative methods available and current consensus in the literature for optimal results. The presented protocol is designed in such a way that investigators without previous knowledge in the field can implement the analysis and obtain viable results that reliably detect significant differences in functional connectivity between experimental groups. Our goal is to empower researchers to implement rs-fMRI in their respective fields by incorporating technical considerations to date into a workable methodological framework.

Probing Intrinsic Resting-State Networks in the Infant Rat Brain.

Resting-state functional magnetic resonance imaging (rs-fMRI) measures spontaneous fluctuations in blood oxygenation level-dependent (BOLD) signal in the absence of external stimuli. It has become a powerful tool for mapping large-scale brain networks in humans and animal models. Several rs-fMRI studies have been conducted in anesthetized and awake adult rats, reporting consistent patterns of brain activity at the systems level. However, the evolution to adult patterns of resting-state activity has not yet been evaluated and quantified in the developing rat brain. In this study, we hypothesized that large-scale intrinsic networks would be easily detectable but not fully established as specific patterns of activity in lightly anesthetized 2-week-old rats (N = 11). Independent component analysis (ICA) identified 8 networks in 2-week-old-rats. These included Default mode, Sensory (Exteroceptive), Salience (Interoceptive), Basal Ganglia-Thalamic-Hippocampal, Basal Ganglia, Autonomic, Cerebellar, as well as Thalamic-Brainstem networks. Many of these networks consisted of more than one component, possibly indicative of immature, underdeveloped networks at this early time point. Except for the Autonomic network, infant rat networks showed reduced connectivity with subcortical structures in comparison to previously published adult networks. Reported slow fluctuations in the BOLD signal that correspond to functionally relevant resting-state networks in 2-week-old rats can serve as an important tool for future studies of brain development in the settings of different pharmacological applications or disease.