Faculty Bibliography

OBJECTIVE:The clinical use of microsignals recorded over broad cortical regions is largely limited by the chronic reliability of the implanted interfaces. APPROACH/METHODS:We evaluated the chronic reliability of novel 61-channel micro-electrocorticographic (µECoG) arrays in rats chronically implanted for over one year and using accelerated aging. Devices were encapsulated with polyimide (PI) or liquid crystal polymer (LCP), and fabricated using commercial manufacturing processes. In vitro failure modes and predicted lifetimes were determined from accelerated soak testing. Successful designs were implanted epidurally over the rodent auditory cortex. Trends in baseline signal level, evoked responses and decoding performance were reported for over one year of implantation. MAIN RESULTS/RESULTS:Devices fabricated with LCP consistently had longer in vitro lifetimes than PI encapsulation. Our accelerated aging results predicted device integrity beyond 3.4 years. Five implanted arrays showed stable performance over the entire implantation period (247-435 days). Our regression analysis showed that impedance predicted signal quality and information content only in the first 31 days of recordings and had little predictive value in the chronic phase (> 31 days). In the chronic phase, site impedances slightly decreased yet decoding performance became statistically uncorrelated with impedance. We also employed an improved statistical model of spatial variation to measure sensitivity to locally varying fields, which is typically concealed in standard signal power calculations. SIGNIFICANCE/CONCLUSIONS:These findings show that µECoG arrays can reliably perform in chronic applications in vivo for over one year, which facilitates the development of a high-density, clinically viable interface.

BACKGROUND:-activated nonselective cation channel, which is enriched in the specialized cardiac conduction system and Purkinje fibers. To date, several putative disease-causing variants in TRPM4 have been reported to be associated with cardiac arrhythmia and progressive conduction disease. Here, we report the functional effects of previously uncharacterized variants of uncertain significance (VUS) that we have found while performing a "genetic autopsy" in individuals who have suffered sudden unexpected death (SUD) in the New York City area. METHODS AND RESULTS/RESULTS:We have identified thirteen uncommon missense VUS in TRPM4 by testing 95 targeted genes implicated in channelopathy and cardiomyopathy in 330 cases of SUD. In several cases there were co-existing VUS in one or more other genes that were tested. We selected four TRPM4 VUS (C20S, A380V, L595V and I1082S) for functional characterization, since these cases lacked detectable variants in other genes of our testing panel. Two of the cases were infants, one was a child and one an adult. RNA-seq data analysis showed that the longer TRPM4b splice variant is predominantly expressed in adult and fetal human heart. We therefore used site-directed mutagenesis to introduce these variants in a TRPM4b cDNA. HEK293 cells were transfected with the cDNAs and patch clamping was performed to assess the functional consequences of the TRPM4 mutants. The TRPM4 current was recorded in excised patches and was significantly reduced by each of the mutants. The total protein level of TRPM4-C20S was markedly decreased, whereas the A380V and L595V mutants exhibited decreased surface expression. The TRPM4-A380V current rapidly desensitized following patch excision. CONCLUSIONS:Each of the VUS tested caused a defect in TRPM4 channel function via distinctly different mechanisms, hence, it lays the foundation for further co-segregation family studies and animal studies of the TRPM4 variants.

Noninvasive brain stimulation techniques are used in experimental and clinical fields for their potential effects on brain network dynamics and behavior. Transcranial electrical stimulation (TES), including transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS), has gained popularity because of its convenience and potential as a chronic therapy. However, a mechanistic understanding of TES has lagged behind its widespread adoption. Here, we review data and modelling on the immediate neurophysiological effects of TES in vitro as well as in vivo in both humans and other animals. While it remains unclear how typical TES protocols affect neural activity, we propose that validated models of current flow should inform study design and artifacts should be carefully excluded during signal recording and analysis. Potential indirect effects of TES (e.g., peripheral stimulation) should be investigated in more detail and further explored in experimental designs. We also consider how novel technologies may stimulate the next generation of TES experiments and devices, thus enhancing validity, specificity, and reproducibility.

Predictive motor control is essential to achieve rapid and precise motor action in all vertebrates. Visuomotor transformations have been a popular model system to study the underlying neural mechanisms in particular the role of the cerebellum in both predictive and gain adaptations. In all species, large-field visual motion produces an involuntary conjugate ocular movement facilitating gaze stabilization called the optokinetic response (OKR). Gain adaptation can be induced by prolonged optokinetic visual stimulation, and if the visual stimulation is temporally periodic, predictive behavior emerges. Two predictive timing components were identifiable in this behavior. The first was prediction of stimulus initiation (when to move) and the other was stimulus termination (when to stop). We designed visual training that allowed us to evaluate initiation and termination independently that included the recording of cerebellar activity followed by acute and chronic cerebellar removal in goldfish of both sexes. We found that initiation and termination predictions were present in the cerebellum and more robust than conflicting visual sensory signals. Each prediction could be acquired independently and both the acquisition and maintenance of each component was cerebellar dependent. Subsequent analysis of the neuronal connectivity strongly supports the hypothesis that the acquired eye velocity behaviors were dependent on feedforward velocity build-up signals from the brainstem, but the adaptive timing mechanism itself originates within the circuitry of the cerebellum.SIGNIFICANCE STATEMENTPredictive and rapid motor control is essential in our daily life such as in the playing of musical instruments or sports. The current work evaluates timing of a visuomotor behavior shown to be similar in humans as well as goldfish. Given the latter species known brainstem cerebellar neuronal connectivity and experimental advantage it was possible to demonstrate the cerebellum to be necessary for acquisition and maintenance of both the initiation and termination components of when to move and to stop. All evidence in this study points to the adaptive predictive control site to lie within the cerebellar circuitry.

Molecular dynamics (MD) simulation using the AMBER force field has been performed on the neurotensin receptor, a class A type G-protein coupled receptor in its activated conformation co-crystallized with the non-peptide agonists. For structure-based hit molecule identification via natural chemical compound library, orthosteric sites on neurotensin receptor have been mapped by docking using AutoDock4.0 and Vina with the known agonists and antagonists SR48692, SR142948, ML301 and ML314 of the receptor. Furthermore, clustering analysis on the MD trajectories by SIMULAID has been performed to filter receptor conformations for the allosteric binders from the Otava natural compound library. Comparative mappings of contrasting binding region patterns have been done between the crystal structure orthosteric sites as well as the binding regions in the SIMULAID-based cluster center conformations from MD trajectories with the FTmap server using the small organic molecule fragments as the probes. The distinct binding region in the cluster-based conformations in the extra-cellular region of the receptor has been identified for targeted docking by Otava natural chemical compound library using AutoDock4.0 and Vina docking suites to obtain putative allosteric binders. A group of compounds from the Otava library has been identified as showing high free energy in both AutoDock4.0 and Vina docking suites. Biophysical assessments on the natural compound computational hit molecules will be done to identify lead structures from the hit molecules.

Eusocial insects live in societies in which distinct family members serve specific roles in maintaining the colony and advancing the reproductive ability of a few select individuals. Given the genetic similarity of all colony members, the diversity of morphologies and behaviors is surprising. Social communication relies on pheromones and olfaction, as shown by mutants of orco, the universal odorant receptor coreceptor, and through electrophysiological analysis of neuronal responses to pheromones. Additionally, neurohormonal factors and epigenetic regulators play a key role in caste-specific behavior, such as foraging and caste switching. These studies start to allow an understanding of the molecular mechanisms underlying social behavior and provide a technological foundation for future studies of eusocial insects. In this review, we highlight recent findings in eusocial insects that advance our understanding of genetic and epigenetic regulations of social behavior and provide perspectives on future studies using cutting-edge technologies. Expected final online publication date for the Annual Review of Genetics Volume 52 is November 23, 2018. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Cortical interneurons display a remarkable diversity in their morphology, physiological properties, and connectivity. Elucidating the molecular determinants underlying this heterogeneity is essential for understanding interneuron development and function. We discovered that alternative splicing differentially regulates the integration of somatostatin- and parvalbumin-expressing interneurons into nascent cortical circuits through the cell-type-specific tailoring of mRNAs. Specifically, we identified a role for the activity-dependent splicing regulator Rbfox1 in the development of cortical interneuron-subtype-specific efferent connectivity. Our work demonstrates that Rbfox1 mediates largely non-overlapping alternative splicing programs within two distinct but related classes of interneurons.

The use of movie-watching as an acquisition state for functional connectivity (FC) MRI has recently enabled multiple groups to obtain rich data sets in younger children with both substantial sample sizes and scan durations. Using naturalistic paradigms such as movies has also provided analytic flexibility for these developmental studies that extends beyond conventional resting state approaches. This review highlights the advantages and challenges of using movies for developmental neuroimaging and explores some of the methodological issues involved in designing pediatric studies with movies. Emerging themes from movie-watching studies are discussed, including an emphasis on intersubject correlations, developmental changes in network interactions under complex naturalistic conditions, and dynamic age-related changes in both sensory and higher-order network FC even in narrow age ranges. Converging evidence suggests an enhanced ability to identify brain-behavior correlations in children when using movie-watching data relative to both resting state and conventional tasks. Future directions and cautionary notes highlight the potential and the limitations of using movies to study FC in pediatric populations.

The cytochalasans are a large family of polyketide natural products with potent bioactivities. Amongst them, the aspochalasins show particularly intricate and fascinating structures. To gain insight into their structural diversity and innate reactivity, we have developed a rapid synthesis of aspochalasin D, the central member of the family. It proceeded in 13 steps starting from divinyl carbinol and utilized a high pressure Diels-Alder reaction that features high regio- and stereoselectivity. So far, our work has culminated in a biomimetic synthesis of aspergillin PZ, an intricate pentacyclic aspochalasan.