The ability to sense the world, process information, and navigate the environment depends on the assembly and continuous function of neural circuits in the brain. Within the past two decades, new technologies have rapidly advanced our understanding of how neural circuits are wired during development and how they are stably maintained, often for years. Electron microscopy reconstructions of model organism connectomes have provided a map of the stereotyped (and variable) connections in the brain; advanced light microscopy techniques have enabled direct observation of the cellular dynamics that underlie circuit construction and maintenance; transcriptomic and proteomic surveys of both developing and mature neurons have provided insights into the molecular and genetic programs governing circuit establishment and maintenance; and advanced genetic techniques have allowed for high-throughput discovery of wiring regulators. These tools have empowered scientists to rapidly generate and test hypotheses about how cir...

The activity and the metabolism of the brain change rhythmically during the day/night cycle. Such rhythmicity is also observed in cultured neurons from the suprachiasmatic nucleus, which is a critical center in rhythm maintenance. However, this issue has not been extensively studied in cultures from areas less involved in timekeeping, as the hippocampus. Using neurons cultured from the hippocampi of newborn rats (both male and female), we observed significant time-dependent changes in global activity, in synaptic vesicle dynamics, in synapse size, and in synaptic mRNA amounts. A transcriptome analysis of the neurons, performed at different times over 24 h, revealed significant changes only for RNA-binding motif 3 (Rbm3). RBM3 amounts changed, especially in synapses. RBM3 knockdown altered synaptic vesicle dynamics and changed the neuronal activity patterns. This procedure also altered local translation in synapses, albeit it left the global cellular translation unaffected. We conclude that hippocampal cult...

The idea that when we use a tool we incorporate it into the neural representation of our body ( embodiment ) has been a major inspiration for philosophy, science and engineering. While theoretically appealing, there is little direct evidence for tool embodiment at the neural level. Using functional magnetic resonance imaging (fMRI) in male and female human subjects, we investigated whether expert tool users (London litter pickers: n=7) represent their expert tool more like a hand (neural embodiment) or less like a hand (neural differentiation), as compared to a group of tool novices (n=12). During fMRI scans, participants viewed first-person videos depicting grasps performed by either a hand, litter picker or a non-expert grasping tool. Using representational similarity analysis, differences in the representational structure of hands and tools were measured within occipitotemporal (OTC). Contrary to the neural embodiment theory, we find that the experts group represent their own tool less like a hand (not ...

The ability to recognize motivationally salient events and adaptively respond to them is critical for survival. Here we tested whether dopamine (DA) neurons in the dorsal raphe nucleus (DRN) contribute to this process in both male and female mice. Population recordings of DRNDA neurons during associative learning tasks showed that their activity dynamically tracks the motivational salience, developing excitation to both reward- and shock-paired cues. The DRNDA response to reward-predicting cues was diminished after satiety, suggesting modulation by internal states. DRNDA activity was also greater for unexpected outcomes than for expected outcomes. Two-photon imaging of DRNDA neurons demonstrated that the majority of individual neurons developed activation to reward-predicting cues and reward but not to shock-predicting cues, which was surprising and qualitatively distinct from the population results. Performing the same fear learning procedures in freely-moving and head-fixed groups revealed that head-fixa...

Neural oscillations play critical roles in information processing, communication between brain areas, learning, and memory. We have recently discovered that familiar visual stimuli can robustly induce 5 Hz oscillations in the primary visual cortex (V1) of awake mice after the visual experience. To gain more mechanistic insight into this phenomenon, we utilized in vivo patch-clamp recordings to monitor the subthreshold activity of individual neurons during these oscillations. We analyzed the visual tuning properties of V1 neurons in naive and experienced mice to assess the effect of visual experience on the orientation and direction selectivity. Using optogenetic stimulation through the patch pipette in vivo, we measured the synaptic strength of specific intracortical and thalamocortical projections in vivo in the visual cortex before and after the visual experience. We found 5 Hz oscillations in membrane potential (Vm) and firing rates evoked in single neurons in response to the familiar stimulus, consiste...

Alpha-synuclein pathology is associated with dopaminergic neuronal loss in the substantia nigra (SN) of Parkinson’s patients. Working across human and mouse models, we investigated mechanisms by which the accumulation of soluble α-synuclein oligomers leads to neurodegeneration. Biochemical analysis of the midbrain of α-synuclein overexpressing BAC-transgenic male and female mice revealed age- and region-dependent mitochondrial dysfunction and accumulation of damaged proteins downstream of the RE1 Silencing Transcription Factor (REST). Vulnerable SN dopaminergic neurons displayed low REST levels compared to neighbouring protected SN GABAergic neurons, which correlated with the accumulation of α-synuclein oligomers and disrupted mitochondrial morphology. Consistent with a protective role, REST levels were reduced in patient iPSC-derived dopaminergic neurons carrying the SNCA-Triplication mutation, which accumulated α-synuclein oligomers and mitochondrial damage, and displayed REST target gene dysregulation. ...

SHANK3 is a large scaffolding protein in the postsynaptic density (PSD) that organizes protein networks, which are critical for synaptic structure and function. The strong genetic association of SHANK3 with autism spectrum disorder (ASD) emphasizes the importance of SHANK3 in neuronal development. SHANK3 has a critical role in organizing excitatory synapses and is tightly regulated by alternative splicing and posttranslational modifications. In this study, we examined basal and activity-dependent phosphorylation of Shank3 using mass spectrometry (MS) analysis from in vitro phosphorylation assays, in situ experiments, and studies with cultured neurons. We found that Shank3 is highly phosphorylated, and we identified serine 782 (S782) as a potent CaMKII phosphorylation site. Using a phosphorylation state-specific antibody, we demonstrate that CaMKII can phosphorylate Shank3 S782 in vitro and in heterologous cells on cotransfection with CaMKII. We also observed an effect of a nearby ASD-associated variant (Sh...

l-DOPA is an effective treatment for Parkinson’s disease (PD); however, long-term treatment induces l-DOPA-induced dyskinesia (LID). To elucidate its pathophysiology, we developed a mouse model of LID by daily administration of l-DOPA to PD male ICR mice treated with 6-hydroxydopamine, and recorded the spontaneous and cortically evoked neuronal activity in the external segment of the globus pallidus (GPe) and substantia nigra pars reticulata (SNr), the connecting and output nuclei of the basal ganglia, respectively, in awake conditions. Spontaneous firing rates of GPe neurons were decreased in the dyskinesia-off state (≥ 24 h after l-DOPA injection) and increased in the dyskinesia-on state (20-100 min after l-DOPA injection while showing dyskinesia), while those of SNr neurons showed no significant changes. GPe and SNr neurons showed bursting activity and low-frequency oscillation in the PD, dyskinesia-off, and dyskinesia-on states. In the GPe, cortically evoked late excitation was increased in the PD and ...

Repetitive behavior is a widely observed neuropsychiatric symptom. Abnormal dopaminergic signaling in the striatum is one of the factors associated with behavioral repetition; however, the molecular mechanisms underlying the induction of repetitive behavior remain unclear. Here, we demonstrated that the NOX1 isoform of the superoxide-producing enzyme NADPH oxidase regulated repetitive behavior in mice by facilitating excitatory synaptic inputs in the central striatum (CS). In male C57Bl/6J mice, repeated stimulation of D2 receptors induced abnormal behavioral repetition and perseverative behavior. Nox1 deficiency or acute pharmacological inhibition of NOX1 significantly shortened repeated D2 receptor stimulation-induced repetitive behavior without affecting motor responses to a single D2 receptor stimulation. Among brain regions, Nox1 showed enriched expression in the striatum, and repeated dopamine D2 receptor stimulation further increased Nox1 expression levels in the CS, but not in the dorsal striatum. ...

P2X7 receptors (P2X7Rs) are associated with numerous pathophysiological mechanisms, and this promotes them as therapeutic targets for certain neurodegenerative conditions. However, the identity of P2X7R-expressing cells in the nervous system remains contentious. Here we examined P2X7R functionality in auditory nerve cells from rodents of either sex, and determined their functional and anatomical expression pattern. In whole-cell recordings from rat spiral ganglion cultures, the purinergic agonist 2’,3’-O-(4-benzoylbenzoyl)-ATP (BzATP) activated desensitizing currents in spiral ganglion neurons (SGNs), but non-desensitizing currents in glia that were blocked by P2X7R-specific antagonists. In imaging experiments, BzATP gated sustained Ca2+ entry into glial cells. BzATP-gated uptake of the fluorescent dye YO-PRO-1 was reduced and slowed by P2X7R-specific antagonists. In rats, P2X7Rs were immuno-localized predominantly within satellite glial cells (SGCs) and Schwann cells (SCs). P2X7R expression was not detect...