Faculty Bibliography

Bone cancer metastasis is extremely painful and decreases the quality of life of the affected patients. Available pharmacological treatments are not able to sufficiently ameliorate the pain and as cancer patients are living longer new treatments for pain management are needed. Decitabine (5-aza-2'-deoxycytidine), a DNA methyltransferases inhibitor, has analgesic properties in pre-clinical models of post-surgical and soft tissue oral cancer pain by inducing an up-regulation of endogenous opioids. In this study, we report that daily treatment with decitabine (2µg/g, i.p.) attenuated nociceptive behavior in the 4T1-luc2 mouse model of bone cancer pain. We hypothesized that the analgesic mechanism of decitabine involved activation of the endogenous opioid system through demethylation and reexpression of the transcriptionally silenced endothelin B receptor gene, Ednrb. Indeed, Ednrb was hypermethylated and transcriptionally silenced in the mouse model of bone cancer pain. We demonstrated that expression of Ednrb in the cancer cells lead to release of β-endorphin in the cell supernatant which reduced the number of responsive DRG neurons in an opioid-dependent manner. Our study supports a role of demethylating drugs, such as decitabine, as unique pharmacological agents targeting the pain in the cancer microenvironment.

Anatomical observations, theoretical work and lesioning experiments have supported the idea that the CA3 in the hippocampus is important for encoding, storage and retrieval of memory while the dentate gyrus (DG) is important for the pattern separation of the incoming inputs from the entorhinal cortex. Study of the presumed function of the dentate gyrus in pattern separation has been hampered by the lack of reliable methods to identify different excitatory cell types in the DG. Recent papers have identified different cell types in the DG, in awake behaving animals, with more reliable methods. These studies have revealed each cell type's spatial representation as well as their involvement in pattern separation. Moreover, chronic electrophysiological recording from sleeping and waking animals also provided more insights into the operation of the DG-CA3 system for memory encoding and retrieval. This article will review the local circuit architectures and physiological properties of the DG-CA3 system and discuss how the local circuit in the DG-CA3 may function, incorporating recent physiological findings in the DG-CA3 system.

Increased reaction time variability (RTV) is one of the most replicable behavioral correlates of attention-deficit/hyperactivity disorder (ADHD). However, this may not be specific to ADHD but a more general marker of psychopathology. Here we compare RT variability in individuals with ADHD and those with other childhood internalizing and externalizing conditions both in terms of standard (i.e., the standard deviation of reaction time) and alternative indices that capture low-frequency oscillatory patterns in RT variations over time thought to mark periodic lapses of attention in ADHD. A total of 667 participants (6-12 years old) were classified into non-overlapping diagnostic groups consisting of children with fear disorders (n = 91), distress disorders (n = 56), ADHD (n = 103), oppositional defiant or conduct disorder (ODD/CD; n = 40) and typically developing controls (TDC; n = 377). We used a simple two-choice reaction time task to measure reaction time. The strength of oscillations in RTs across the session was extracted using spectral analyses. Higher RTV was present in ADHD compared to all other disorder groups, effects that were equally strong across all frequency bands. Interestingly, we found that lower RTV to characterize ODD/CD relative to TDC, a finding that was more pronounced at lower frequencies. In general, our data support RTV as a specific marker of ADHD. RT variation across time in ADHD did not show periodicity in a specific frequency band, not supporting that ADHD RTV is the product of spontaneous periodic lapses of attention. Low-frequency oscillations may be particularly useful to differentiate ODD/CD from TDC.

Introduction: The mammalian enteric nervous system (ENS) regulates intestinal function in response to luminal changes in nutrients and microbiota. The ENS also modulates immune cells to control microbial homeostasis and fight infections. Enteric neurons signal to the brain via the vagus nerve, providing a mechanism by which microbiota can influence neural activity and behavior at homeostasis or during infections with gut pathogens. However, little is known about the relation between vagus nerve activity and 'sickness behaviors' such as decreased attention, increased irritability and depression, and decreased interest and energy. Here we aimed to record vagus nerve responses in behaving animals towards understanding this gut-brain signaling connection in sickness behavior. Method(s): Custom nerve cuff electrodes were used to monitor vagus nerve activity of wild-type male mice. Cuffs were made with 0.2 mm micro-renathane tubing to surround the upper branch of the sensory vagus nerve and connected to socket gold pins and medwire. Chronic nerve cuffs were implanted in mice aged 6-12 weeks. Surgery consisted of securing gold pins to the cranial vertex and connecting electrodes to the vagus nerve in the neck, around which the cuff was placed. The grounding wire was secured near the cuff. One to two weeks post-surgery, each mouse underwent sickness induction via lipopolysaccharide (LPS) injection. LPS solution was formulated with 9.5/g muL of 0.9% saline solution and 0.5/g muL of pure LPS via intraperitoneal injection. Electrophysiological activity of the vagus nerve was recorded together with video monitoring of behavior, prior to injection to first establish a baseline, and post-injection activity was recorded for up to 24 hours. Sickness behavior was ethogrammed and neural activity analyzed in each animal. Result(s): LPS injection led to reduction of several different behaviors including overall motion in the homecage for hours afterwards. Analysis of simultaneously-recorded vagus activity is ongoing. Conclusion(s): We here describe an integrated system that combines long-term videography and behavioral analysis with recordings of the peripheral nerve activity using a custom chronic nerve cuff for the mouse vagus. Using this system, we have begun to relate neural activity in the sensory vagus to physiological state and behavioral changes in mice for the first time.

Transcutaneous electric stimulation (TES) using weak currents has been used extensively in attempts to influence brain activity. In vitro and in vivo experiments in rodents and computational modeling suggest that the magnitude of voltage gradient of the induced electric field should exceed 1 mV/mm to instantaneously and reproducibly alter neuronal spiking and consequent brain network patterns. Evidence for immediate and unconditional neuronal effects of TES in the human brain is still lacking, mainly due to the saturation of the recording amplifiers by the large induced electromagnetic fields. For many therapeutic applications, it is desirable to affect neurons in a regionally constrained manner to reach maximum on-target effects and reduce side effects on unintended brain networks. Here, we determine the needed TES currents in human cadavers to achieve 1 mV/mm fields. Scalp stimulation greatly reduced the generated intracerebral electric fields (>50% in cadavers) and these measurements predicted that ~5 mA is needed to achieve 1mV/mm electric field gradient via scalp stimulation. To reach the desired intracerebral field strength without the adverse peripheral effects of >5 mA currents, we introduce a spatially focused multiple site, Intersectional Short-Pulse (ISP) stimulation. We demonstrate the instantaneous entraining effect of ISP on alpha waves in human subjects and on neuronal spiking in rats. Immediate effects of TES can be best utilized in disorders with sudden, major electrographic changes such as epileptic seizures. We showed earlier that thalamocortical seizures can be quickly terminated by temporally targeted, diffuse transcranial stimulation, however secondarily generalized temporal lobe seizures are more resistant to these diffuse interference interventions. ISP also has the capacity to spatially focus its effect, thus it is capable to overcome the unwanted mirror effect (anodal vs cathodal) of the traditional TES protocols. We report here a novel stimulation pattern, that can simultaneously entrain both hippocampi. To evaluate its utility, temporal lobe seizures were induced in rats by electrical kindling, and each electrically kindled seizures were automatically detected and silenced by a closed loop ISP stimulation. By comparing to closed-loop diffuse TES, we found that ISP with bilateral foci is more effective in early seizure termination. Lastly, we introduce our prototyping efforts to implement an implantable, minimal-invasive, transcranial closed-loop seizure termination device, aiming for human clinical applications.

Introduction: Vagus nerve stimulation is currently used as a medical treatment for those suffering from severe epilepsy or depression, but the mechanisms underlying vagus nerve stimulation are poorly understood. The vagus nerve helps connect essentially all peripheral organs to the central nervous system, sending afferents to the nucleus tractus solitarius. Recent studies indicate that vagus nerve stimulation can produce long-lasting plasticity in the cerebral cortex, leading to improved sensory processing and recovery of motor behavior after stroke (Boreland et al, Brain Stimul (2016). An understanding of the circuit mechanisms by which vagus nerve stimulation can produce these results would be important for enhancing behavioral outcomes and developing less invasive or non-invasive neuromodulatory therapeutic techniques. Method(s): Studies in mice provide an opportunity for monitoring and manipulating various aspects of neural circuits involved in behavior. One difficulty in the mouse model is the lack of vagus nerve cuff electrodes given the small size of the mouse vagus nerve. We first built a novel vagus nerve cuff electrode for mice and demonstrated reliable low-impedance recordings and stimulation during behavior in mice chronically implanted for months. Two-photon imaging of the auditory cortex was used to track neural responses to tones paired with vagus nerve stimulation. Animals are then trained on either a paired go/no-go or two-alternative forced choice auditory detection and recognition task (Martins and Froemke, Nat Neurosci 2015; Kuchibhotla et al. Nat Neurosci 2017). Result(s): Stimulation of the vagus nerve was calibrated to transiently reduce respiration without affecting other physiological processes (e.g., heart rate). Using two-photon imaging, we found that pairing target tones with vagus nerve stimulation for five minutes led to a short-term enhancement of sensory responses in the mouse auditory cortex. After several days of these brief 5-minute pairing sessions, long-term plasticity was observed with increases in representation of the target tone for at least days thereafter. Conclusion(s): These changes are reminiscent of the effects of basal forebrain stimulation (Froemke et al. Nature 2007) and we are now investigating how vagus nerve stimulation might lead to direct or indirect activation of central modulatory systems to improve plasticity and behavior in mice.

BACKGROUND:Genetic variation in ion channel genes ('channelopathies') are often associated with inherited arrhythmias and sudden death. Genetic testing ('molecular autopsies') of channelopathy genes can be used to assist in determining the likely causes of sudden unexpected death. However, different in silico approaches can yield conflicting pathogenicity predictions and assessing their impact on ion channel function can assist in this regard. METHODS AND RESULTS/RESULTS:channels, as determined with biotinylation assays, suggesting that all of the variants led to an enhanced open state. CONCLUSIONS:channels in the heart and specialized cardiac conduction, vascular smooth muscle and respiratory neurons, it is conceivable that electrical silencing of these cells may contribute to the vulnerability element, which is a component of the triple risk model of sudden explained death in infants. The gain-of-function phenotype of these ABCC9 variants should be considered when assessing their potential pathogenicity.

Targeting tau with immunotherapies is currently the most common approach taken in clinical trials of patients with Alzheimer's disease. The most prominent pathological feature of tau is its hyperphosphorylation, which may cause the protein to aggregate into toxic assemblies that collectively lead to neurodegeneration. Of the phospho-epitopes, the region around Ser³⁹⁶/Ser⁴⁰⁴ has received particular attention for therapeutic targeting because of its prominence and stability in diseased tissue. Herein, we present the antigen-binding fragment (Fab)/epitope complex structures of three different monoclonal antibodies (mAbs) that target the pSer⁴⁰⁴ tau epitope region. Most notably, these structures reveal an antigen conformation similar to a previously described pathogenic tau epitope, pSer⁴²², which was shown to have a β-strand structure that may be linked to the seeding core in tau oligomers. In addition, we have previously reported on the similarly ordered conformation observed in a pSer³⁹⁶ epitope, which is in tandem with pSer⁴⁰⁴. Our data are the first Fab structures of mAbs bound to this epitope region of the tau protein and support the existence of proteopathic tau conformations stabilized by specific phosphorylation events that are viable targets for immune modulation. The atomic coordinates and structure factors have been deposited in the RCSB Protein Data Bank under accession codes 6DC7 (8B2 apo), 6DC8 (8B2), 6DC9 (h4E6), and 6DCA (6B2).

OBJECTIVE:Sleep spindles have been implicated in memory consolidation and synaptic plasticity during NREM sleep. Detection accuracy and latency in automatic spindle detection are critical for real-time applications. APPROACH/METHODS:Here we propose a novel deep learning strategy (SpindleNet) to detect sleep spindles based on a single EEG channel. While the majority of spindle detection methods are used for off-line applications, our method is well suited for online applications. MAIN RESULTS/RESULTS:Compared with other spindle detection methods, SpindleNet achieves superior detection accuracy and speed, as demonstrated in two publicly available expert-validated EEG sleep spindle datasets. Our real-time detection of spindle onset achieves detection latencies of 150-350 ms (~2-3 spindle cycles) and retains excellent performance under low EEG sampling frequencies and low signal-to-noise ratios. SpindleNet has good generalization across different sleep datasets from various subject groups of different ages and species. SIGNIFICANCE/CONCLUSIONS:SpindleNet is ultra-fast and scalable to multichannel EEG recordings, with an accuracy level comparable to human experts, making it appealing for long-term sleep monitoring and closed-loop neuroscience experiments. &#13.

BACKGROUND:, P-tau, and T-tau with sleep spindle density and other biophysical properties of sleep spindles in a sample of cognitively normal elderly individuals. METHODS:, P-tau and T-tau. Seven days of actigraphy were collected to assess habitual total sleep time. RESULTS:, P-tau and T-tau. From the three, CSF T-tau was the most significantly associated with spindle density, after adjusting for age, sex and ApoE4. Spindle duration, count and fast spindle density were also negatively correlated with T-tau levels. Sleep duration and other measures of sleep quality were not correlated with spindle characteristics and did not modify the associations between sleep spindle characteristics and the CSF biomarkers of AD. CONCLUSIONS:Reduced spindles during N2 sleep may represent an early dysfunction related to tau, possibly reflecting axonal damage or altered neuronal tau secretion, rendering it a potentially novel biomarker for early neuronal dysfunction. Given their putative role in memory consolidation and neuroplasticity, sleep spindles may represent a mechanism by which tau impairs memory consolidation, as well as a possible target for therapeutic interventions in cognitive decline.