Understanding the human conflict processing network: A review of the literature on direct neural recordings during performance of a modified stroop task

The Stroop Task is a well-known neuropsychological task developed to investigate conflict processing in the human brain. Our group has utilized direct intracranial neural recordings in various brain regions during performance of a modified color-word Stroop Task to gain a mechanistic understanding of non-emotional human conflict processing. The purpose of this review article is to: 1) synthesize our own studies into a model of human conflict processing, 2) review the current literature on the Stroop Task and other conflict tasks to put our research in context, and 3) describe how these studies define a network in conflict processing. The figures presented are reprinted from our prior publications and key publications referenced in the manuscript. We summarize all studies to date that employ invasive intracranial recordings in humans during performance of conflict-inducing tasks. For our own studies, we analyzed local field potentials (LFPs) from patients with implanted stereotactic electroencephalography (SEEG) electrodes, and we observed intracortical oscillation patterns as well as intercortical temporal relationships in the hippocampus, amygdala, and orbitofrontal cortex (OFC) during the cue-processing phase of a modified Stroop Task. Our findings suggest that non-emotional human conflict processing involves modulation across multiple frequency bands within and between brain structures.

Protocol for a scoping review of factors associated with disparities in clinical provision of deep brain stimulation

INTRODUCTION

Deep brain stimulation (DBS) can be used to treat several neurological and psychiatric conditions such as Parkinson's disease, epilepsy and obsessive-compulsive disorder; however, limited work has been done to assess the disparities in DBS access and implementation. The goal of this scoping review is to identify sources of disparity in the clinical provision of DBS.

METHODS AND ANALYSIS

A scoping review will be conducted based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses-extension for Scoping Reviews methodology. Relevant studies will be identified from databases including MEDLINE/PubMed, EMBASE and Web of Science, as well as reference lists from retained articles. Initial search dates were in January 2023, with the study still ongoing. An initial screening of the titles and abstracts of potentially eligible studies will be completed, with relevant studies collected for full-text review. The principal investigators and coauthors will then independently review all full-text articles meeting the inclusion criteria. Data will be extracted and collected in table format. Finally, results will be synthesised in a table and narrative report.

ETHICS AND DISSEMINATION

No institutional board review or approval is necessary for the proposed scoping review. The findings will be submitted for publication to relevant peer-reviewed journals and conferences.

SCOPING REVIEW REGISTRATION

This protocol has been registered prospectively on the Open Science Framework (https://osf.io/cxvhu).

A review of neurophysiological effects and efficiency of waveform parameters in deep brain stimulation

Neurostimulation has diverse clinical applications and potential as a treatment for medically refractory movement disorders, epilepsy, and other neurological disorders. However, the parameters used to program electrodes-polarity, pulse width, amplitude, and frequency-and how they are adjusted have remained largely untouched since the 1970 s. This review summarizes the state-of-the-art in Deep Brain Stimulation (DBS) and highlights the need for further research to uncover the physiological mechanisms of neurostimulation. We focus on studies that reveal the potential for clinicians to use waveform parameters to selectively stimulate neural tissue for therapeutic benefit, while avoiding activating tissue associated with adverse effects. DBS uses cathodic monophasic rectangular pulses with passive recharging in clinical practice to treat neurological conditions such as Parkinson's Disease. However, research has shown that stimulation efficiency can be improved, and side effects reduced, through modulating parameters and adding novel waveform properties. These developments can prolong implantable pulse generator lifespan, reducing costs and surgery-associated risks. Waveform parameters can stimulate neurons based on axon orientation and intrinsic structural properties, providing clinicians with more precise targeting of neural pathways. These findings could expand the spectrum of diseases treatable with neuromodulation and improve patient outcomes.

Racial disparities in access to DBS: results of a real-world U.S. claims data analysis

Introduction

Deep brain stimulation (DBS) is an effective and standard-of-care therapy for Parkinson's Disease and other movement disorders when symptoms are inadequately controlled with conventional medications. It requires expert care for patient selection, surgical targeting, and therapy titration. Despite the known benefits, racial/ethnic disparities in access have been reported. Technological advancements with smartphone-enabled devices may influence racial disparities. Real-world evidence investigations can shed further light on barriers to access and demographic disparities for DBS patients.

Methods

A retrospective cross-sectional study was performed using Medicare claims linked with manufacturer patient data tracking to analyze 3,869 patients who received DBS. Patients were divided into two categories: traditional omnidirectional DBS systems with dedicated proprietary controllers ("traditional"; n = 3,256) and directional DBS systems with smart controllers ("smartphone-enabled"; n = 613). Demographics including age, sex, and self-identified race/ethnicity were compared. Categorical demographics, including race/ethnicity and distance from implanting facility, were analyzed for the entire population.

Results

A significant disparity in DBS utilization was evident. White individuals comprised 91.4 and 89.9% of traditional and smartphone-enabled DBS groups, respectively. Non-White patients were significantly more likely to live closer to implanting facilities compared with White patients.

Conclusion

There is great racial disparity in utilization of DBS therapy. Smartphone-enabled systems did not significantly impact racial disparities in receiving DBS. Minoritized patients were more likely to live closer to their implanting facility than White patients. Further research is warranted to identify barriers to access for minoritized patients to receive DBS. Technological advancements should consider the racial discrepancy of DBS utilization in future developments.

Neuromodulation of OCD: A review of invasive and non-invasive methods

Early research into neural correlates of obsessive compulsive disorder (OCD) has focused on individual components, several network-based models have emerged from more recent data on dysfunction within brain networks, including the the lateral orbitofrontal cortex (lOFC)-ventromedial caudate, limbic, salience, and default mode networks. Moreover, the interplay between multiple brain networks has been increasingly recognized. As the understanding of the neural circuitry underlying the pathophysiology of OCD continues to evolve, so will too our ability to specifically target these networks using invasive and noninvasive methods. This review discusses the rationale for and theory behind neuromodulation in the treatment of OCD.

Dopamine decreases NMDA currents in the oval bed nucleus of the stria terminalis of cocaine self-administering rats

Dopamine (DA) and N-methyl-D-aspartate receptors (NMDARs) contribute in the neural processes underlying drug-driven behaviors. DA is a potent modulator of NMDAR, but few studies have investigated the functional interaction between DA and NMDAR in the context of substance abuse. We combined the rat model of cocaine self-administration with brain slice electrophysiology to study DA modulation of NMDA currents in the oval bed nucleus of the stria terminalis (ovBNST), a dense DA terminal field involved in maintenance of cocaine self-administration amongst other drug related behaviors. Long-Evans rats self-administered intravenous cocaine (0.75 mg/kg/injection) on a progressive ratio (PR) schedule of reinforcement for 15 days and whole-cell patch-clamp recordings were done on the 16th day. DA reduced NMDA currents in brain-slices from cocaine self-administering rats, but not in those of drug-naïve and sucrose self-administering, or when cocaine exposure was passive (yoked), revealing a mechanism unique to voluntary cocaine intake. DA reduced NMDA currents by activating G-protein-coupled D1- and D2-like receptors that converged on phospholipase C and protein phosphatases. Accordingly, our study reveals a mechanism that may contribute to dysfunctional synaptic plasticity associated with drug-driven behaviors during acute withdrawal.

Timing of myocardial trpm7 deletion during cardiogenesis variably disrupts adult ventricular function, conduction, and repolarization

BACKGROUND

Transient receptor potential (TRP) channels are a superfamily of broadly expressed ion channels with diverse physiological roles. TRPC1, TRPC3, and TRPC6 are believed to contribute to cardiac hypertrophy in mouse models. Human mutations in TRPM4 have been linked to progressive familial heart block. TRPM7 is a divalent-permeant channel and kinase of unknown function, recently implicated in the pathogenesis of atrial fibrillation; however, its function in ventricular myocardium remains unexplored.

METHODS AND RESULTS

We generated multiple cardiac-targeted knockout mice to test the hypothesis that TRPM7 is required for normal ventricular function. Early cardiac Trpm7 deletion (before embryonic day 9; TnT/Isl1-Cre) results in congestive heart failure and death by embryonic day 11.5 as a result of hypoproliferation of the compact myocardium. Remarkably, Trpm7 deletion late in cardiogenesis (about embryonic day 13; αMHC-Cre) produces viable mice with normal adult ventricular size, function, and myocardial transcriptional profile. Trpm7 deletion at an intermediate time point results in 50% of mice developing cardiomyopathy associated with heart block, impaired repolarization, and ventricular arrhythmias. Microarray analysis reveals elevations in transcripts of hypertrophy/remodeling genes and reductions in genes important for suppressing hypertrophy (Hdac9) and for ventricular repolarization (Kcnd2) and conduction (Hcn4). These transcriptional changes are accompanied by action potential prolongation and reductions in transient outward current (Ito; Kcnd2). Similarly, the pacemaker current (If; Hcn4) is suppressed in atrioventricular nodal cells, accounting for the observed heart block.

CONCLUSIONS

Trpm7 is dispensable in adult ventricular myocardium under basal conditions but is critical for myocardial proliferation during early cardiogenesis. Loss of Trpm7 at an intermediate developmental time point alters the myocardial transcriptional profile in adulthood, impairing ventricular function, conduction, and repolarization.

Abstract 48: Cardiac-Targeted TRPM7 Deletion Induces Cardiomyopathy, Heart Block and Impaired Ventricular Repolarization via Downregulation of Kcnd2 and Hcn4

Transient Receptor Potential Melastatin-7 (TRPM7) is a divalent permeant channel-kinase of unknown function. It is concentrated in myocardium during embryonic development, and TRPM7-like current has been reported in adult ventricular myocytes. In atrial cardiac fibroblasts, TRPM7 has been implicated in fibrogenesis in patients with atrial fibrillation, however its function in ventricular myocardium is unexplored. We tested the hypothesis that TRPM7 is required for ventricular function by crossing TRPM7fl/- mice with the cardiac-targeted αMHC-Cre line (αMHC-TRPM7 KO). We show that TRPM7 forms a functional current in adult murine ventricular cardiomyocytes and demonstrate that ∼50% of αMHC-TRPM7 KO mice develop a cardiomyopathy with left ventricular dysfunction and cardiac hypertrophy, associated with heart block and impaired ventricular repolarization. This phenotype is associated with robust elevations in mRNA of Postn, Nppa, Timp1, Acta and reductions in Hdac9, Kcnv2, Kcnj3, Kcnd2, Lgi1 and Hcn4. Consistent with mRNA expression analysis and the observed electrical remodeling, patch-clamp of αMHC-Cre-TRPM7 KO ventricular myocytes (RV and LV) reveals significant action potential prolongation (2.5 to 4-fold increase in APD50) due to a 2 to 4-fold reduction in transient outward current (Ito, encoded by Kcnd2). Similarly, the funny current (If), encoded by Hcn4, is diminished 4-fold in atrioventricular nodal cells isolated from αMHC-Cre-Trpm7 KO hearts, accounting for the observed heart block. The ∼50% of αMHC-Cre-Trpm7 KO mice that do not develop cardiomyopathy are devoid of heart block, show normal expression levels of hypertrophy genes Postn, Nppa, and Acta, but continue to show significant reductions in Kcnd2, Lgi1, Kcnj3, Kcnv2, and Hdac9 expression. In conclusion, these results demonstrate that cardiac-targeted TRPM7 deletion dysregulates the expression of ion channels important for cardiomyocyte repolarization (Kcnd2) and atrioventricular conduction (Hcn4), leading to impaired ventricular repolarization and heart block in mice. The observed cardiomyopathy may arise from hemodynamic stresses secondary to chronic bradycardia from heart block in the setting of down-regulated histone deacetylase 9 (HDAC9).

Double-dissociation of the catecholaminergic modulation of synaptic transmission in the oval bed nucleus of the stria terminalis

The bed nucleus of the stria terminalis (BST) is a cluster of nuclei within the extended amygdala, a forebrain macrostructure with extensive projection to motor nuclei of the hindbrain. The subnuclei of the BST coordinate autonomic, neuroendocrine, and somato-motor functions and receive robust neuromodulatory monoaminergic afferents, including 5-HT-, noradrenaline (NA)-, and dopamine (DA)-containing terminals. In contrast to 5-HT and NA, little is known about how DA modulates neuronal activity or synaptic transmission in the BST. DA-containing afferents to the BST originate in the ventral tegmental area, the periaqueducal gray, and the retrorubral field. They form a fairly diffuse input to the dorsolateral BST with dense terminal fields in the oval (ovBST) and juxtacapsular (jxBST) nuclei. The efferent-afferent connectivity of the BST suggests that it may play a key role in motivated behaviors, consistent with recent evidence that the dorsolateral BST is a target for drugs of abuse. This study describes the effects of DA on synaptic transmission in the ovBST. Whole cell voltage clamp recordings were performed on ovBST neurons in brain slices from adult rats in the presence or absence of exogenous DA and receptor-targeted agonists and antagonists. The results showed that DA selectively and exclusively reduced inhibitory synaptic transmission in the ovBST in a dose-dependent and D2-like dopamine receptor-dependent manner. DA also modulated excitatory synaptic transmission in a dose-dependent dependent manner. However, this effect was mediated by α2-noradrenergic receptors. Thus these data reveal a double dissociation in catecholaminergic regulation of excitatory and inhibitory synaptic transmission in the ovBST and may shed light on the mechanisms involved in neuropathological behaviors such as stress-induced relapse to consumption of drugs of abuse.

Creation of a functional tricuspid valve: novel use of percutaneously implanted valve in right atrial to right ventricular conduit in a patient with tricuspid atresia

We report the first use of a stented pulmonic valve within the right atrial to right ventricular conduit of a patient who underwent a Björk modification Fontan for tricuspid atresia. In effect, a functional tricuspid valve was created. This case report demonstrates the feasibility of transcatheter valve replacement in positions other than the pulmonic or aortic valve and that future revision of conduits in the Björk modification Fontan can be performed percutaneously.