Cholinergic projections from the medial habenula (MHb) to the interpeduncular nucleus (IPN) have been studied for their complex contributions to nicotine addiction and have been implicated in nicotine reinforcement, aversion, and withdrawal. While it has been established that MHb cholinergic projections corelease glutamate, no direct evidence has demonstrated a role for this glutamate projection in nicotine consumption. In the present study, a novel floxed Slc17a7 [vesicular glutamate transporter 1 (VGLUT1)] mouse was generated and used to create conditional knock-out (cKO) mice that lack VGLUT1 in MHb cholinergic neurons. Loss of Slc17a7 expression in ventral MHb cholinergic neurons was validated using fluorescent in situ hybridization, and immunohistochemistry was used to demonstrate a corresponding reduction of VGLUT1 protein in cholinergic terminals in the IPN. We also used optogenetics-assisted electrophysiology to evoke EPSCs in IPN and observed a reduction of glutamatergic currents in the cKO, suppo...

Emotional states provide an ever-present source of contextual information that should inform behavioral goals. Despite the ubiquity of emotional signals in our environment, the neural mechanisms underlying their influence on goal-directed action remains unclear. Prior work suggests that the lateral frontal pole (FPl) is uniquely positioned to integrate affective information into cognitive control representations. We used pattern similarity analysis to examine the content of representations in FPl and interconnected mid-lateral prefrontal and amygdala circuitry. Healthy participants (n=37; n=21 females) were scanned while undergoing an event-related Affective Go/No-Go task, which requires goal-oriented action selection during emotional processing. We found that FPl contained conjunctive emotion-action goal representations that were related to successful cognitive control during emotional processing. These representations differed from conjunctive emotion-action goal representations found in the basolateral ...

Employing postsynaptically tethered calcium sensor GCaMP, we investigated spontaneous synaptic transmission at individual active zones (AZs) at the Drosophila (both sexes) neuromuscular junction. Optical monitoring of GCaMP events coupled with focal electrical recordings of synaptic currents revealed “hot spots” of spontaneous transmission, which corresponded to transient states of elevated activity at selected AZs. The elevated spontaneous activity had two temporal components, one at a timescale of minutes and the other at a sub-second timescale. We developed a three-state model of AZ preparedness for spontaneous transmission and performed Monte-Carlo simulations of the release process, which produced an accurate quantitative description of the variability and time-course of spontaneous transmission at individual AZs. To investigate the mechanisms of elevated activity, we first focused on the protein complexin, which binds the SNARE protein complex and serves to clamp spontaneous fusion. Overexpression of...

A main characteristic of dyslexia is poor use of sound categories. We now studied within-session learning of new sound categories in dyslexia – behaviorally and neurally, using fMRI. Human participants (males and females) with and without dyslexia were asked to discriminate which of two serially-presented tones had a higher pitch. The task was administered in two protocols, with and without a repeated reference frequency. The reference condition introduces regularity, and enhances frequency sensitivity in typically developing (TD) individuals. Enhanced sensitivity facilitates the formation of “high” and “low” pitch categories above and below this reference, respectively. We found that in TDs, learning was paralleled by a gradual decrease in activation of the primary auditory cortex, and reduced activation of the superior temporal gyrus and left posterior parietal cortex, which are important for utilizing sensory history. No such sensitivity was found among individuals with dyslexia (IDDs). Rather, IDDs sho...

Mechanisms underlying the initial accumulation of tau pathology across the human brain are largely unknown. We examined whether baseline factors including age, amyloid-β, and neural activity predicted longitudinal tau accumulation in temporal lobe regions that reflect distinct stages of tau pathogenesis. Seventy cognitively normal human older adults (77±6 years, 59% female) received ≥2 18F-Flortaucipir (FTP) and 11C-Pittsburgh Compound B (PiB) PET scans (2.5±1.1 years follow-up) to quantify tau and amyloid-β. Linear mixed effects models were used to calculate slopes of FTP change in entorhinal cortex (EC), parahippocampal cortex (PHC), and inferior temporal gyrus (IT), and slopes of global PiB change. Thirty-seven participants received functional MRI to measure baseline activation. Older age predicted EC tau accumulation, and baseline EC tau predicted subsequent tau accumulation in EC and PHC. In IT, however, baseline EC tau interacted with Aβ to predict IT tau accumulation. Higher baseline local activatio...

In the mammalian brain perivascular astrocytes (PAs) closely juxtapose blood vessels and are postulated to have important roles in the control of vascular physiology, including regulation of the blood-brain barrier (BBB). Deciphering specific functions for PAs in BBB biology, however, has been limited by the ability to distinguish these cells from other astrocyte populations. In order to characterize selective roles for PAs in vivo, a new mouse model has been generated in which the endogenous megalencephalic leukoencephalopathy with subcortical cysts 1 (Mlc1) gene drives expression of Cre fused to a mutated estrogen ligand-binding domain (Mlc1-T2A-CreERT2). This knock-in mouse model, which we term MLCT, allows for selective identification and tracking of PAs in the post-natal brain. We also demonstrate that MLCT-mediated ablation of PAs causes severe defects in BBB integrity, resulting in premature death. PA loss results in aberrant localization of Claudin 5 and VE-Cadherin in endothelial cell junctions as...

While opioids produce both analgesia and side-effects by action at mu-opioid receptors (MOR), at spinal and supraspinal sites, potency of different opioids to produce these effects vary. While it has been suggested that these differences might be due to bias for signaling via β-arrestin versus G protein alpha (Gα), recent studies suggest that G protein biased MOR agonists still produce clinically important side-effects. Since bias also exists in the role of Gα subunits, we evaluated the role of Gαi/o subunits in analgesia, hyperalgesia, and hyperalgesic priming produced by fentanyl and morphine, in male rats. We found that intrathecal treatment with oligodeoxynucleotides antisense (AS-ODN) for Gαi2, Gαi3 and Gαo markedly attenuated hyperalgesia induced by sub-analgesic dose (sub-AD) fentanyl, while AS-ODN for Gαi1, as well as Gαi2 and Gαi3, but not Gαo, prevented hyperalgesia induced by sub-AD morphine. AS-ODN for Gαi1 and Gαi2 unexpectedly enhanced analgesia induced by analgesic dose (AD) fentanyl, while ...

The physical interaction and functional cross-talk among the different subtypes of neuronal nicotinic receptors (nAChRs) expressed in the various tissues is unknown. Here we have investigated this issue between the only two nAChRs subtypes expressed, the α7 and α3β4 subtypes, in a human native neuroendocrine cell (the chromaffin cell) using electrophysiological patch-clamp, fluorescence, and FRET techniques. Our data show that α7 and α3β4 receptor subtypes require their mutual and maximal efficacy of activation to increase their expression, to avoid their desensitization, and therefore, to increase their activity. In this way, after repetitive stimulation with acetylcholine (ACh), α7 and α3β4 receptor subtypes do not desensitize, but they do with choline. The nicotinic current increase associated with the α3β4 subtype is dependent on Ca2+. In addition, both receptor subtypes physically interact. Interaction and expression of both subtypes are reversibly reduced by tyrosine and serine/threonine phosphatases...

The prefrontal cortex (PFC) and insula, amygdala, and striatum form interconnected networks that drive motivated behaviors. We previously found a connectional trend in which granularity of the ventromedial and orbital PFC/insula predicted connections to the amygdala, and also the breadth of amygdalo-striatal efferents, including projections beyond the 'classic' ventral striatum. To further interrogate connectional relationships among the cortex, amygdala, and striatum, and to further define the 'limbic (amygdala-recipient) striatum', we conducted tract tracing studies in two cohorts of Macaques (Male n = 14, Female n = 1). We focused on the cortico-amygdalo-striatal (indirect) and cortico-‘limbic’ striatal (direct) paths originating in the entire PFC and insula. Larger data sets and a quantitative approach revealed 'cortical rules' in which cortical granularity predicts the complexity and location of projections to both the basal nucleus of the amygdala and striatum. Remarkably, projections from 'cortical-...

Narrowband gamma oscillations (NBG: ∼20-60Hz) in visual cortex reflect rhythmic fluctuations in population activity generated by underlying circuits tuned for stimulus location, orientation, and color. A variety of theories posit a specific role for NBG in encoding and communicating this information within visual cortex. However, recent findings suggest a more nuanced role for NBG, given its dependence on certain stimulus feature configurations, such as coherent oriented edges and specific hues. Motivated by these factors, we sought to quantify the independent and joint tuning properties of NBG to oriented and color stimuli using intracranial recordings from the human visual cortex (male & female). NBG was shown to display a cardinal orientation bias (horizontal) and also an end- and mid-spectral color bias (red/blue and green). When jointly probed, the cardinal bias for orientation was attenuated and an end-spectral preference for red and blue predominated. This loss of mid-spectral tuning occurred even f...