Journal of Neuroscience最新文献

A dynamic interplay between fast synaptic signals and slower neuromodulatory signals controls the excitatory-inhibitory (E/I) balance within neuronal circuits. The mechanisms by which neuropeptide signaling is regulated to maintain E/I balance remain uncertain. We designed a genetic screen to isolate genes involved in the peptidergic maintenance of the E/I balance in the C. elegans motor circuit. This screen identified the C. elegans orthologs of the presynaptic phosphoprotein Synapsin (snn-1) and the Protein Phosphatase 1 (PP1) regulatory subunit PHACTR1 (phac-1). We demonstrate that both phac-1 and snn-1 alter the motor behavior of C. elegans, and genetic interactions suggest that SNN-1 contributes to PP1-PHAC-1 holoenzyme signaling. De novo variants of human PHACTR1, associated with early-onset epilepsies (DEE70), when expressed in C. elegans resulted in constitutive PP1-PHAC-1 holoenzyme activity. Unregulated PP1-PHAC-1 signaling alters the Synapsin and Actin cytoskeleton and increases neuropeptide release by cholinergic motor neurons, which secondarily affects the presynaptic vesicle cycle. Together, these results clarify the dominant mechanisms of action of the DEE70 alleles and suggest that altered neuropeptide release may alter E/I balance in DEE70.Significance Statement Alterations of the excitatory-inhibitory (E/I) balance within neuronal circuits contribute to seizures. Early-onset epilepsies are associated with 4 variants of human PHACTR1 (called DEE70). In a genetic screen designed to isolate genes involved in the maintenance of the E/I balance by peptidergic neuromodulators, we identified the C. elegans orthologs of PHACTR1 and of Synapsin. When introduced in C. elegans, the DEE70-associated variants reduced the E/I balance in motor circuits. Our results suggest that DEE70 variants induce the constitutive activity of an holophosphatase formed by PHACTR1. The constitutive holophosphatase signaling alters the Synapsin and Actin cytoskeleton and increases neuropeptide release which secondarily decreases E/I balance in circuits.

Endoplasmic reticulum (ER) stress is crucial in cerebral ischemia/reperfusion injury by triggering cellular apoptosis and exacerbating neuronal damage. This study elucidates the dynamics of TP53-induced glycolysis and apoptosis regulator (TIGAR) translocation and its role in regulating neural fate during cerebral ischemia-induced ER stress, specifically in male mice. We found enhanced nuclear localization of TIGAR in neurons after transient middle cerebral artery occlusion/reperfusion (tMCAO/R) in male mice, as well as oxygen glucose deprivation/reperfusion (OGD/R) and treatment with ER stress inducer (tunicamycin and thapsigargin) in neuronal cells. Conditional neuronal knockdown of Tigar aggravated the injury following ischemia-reperfusion, whereas overexpression of Tigar attenuated cerebral ischemic injury and ameliorated intra-neuronal ER stress. Additionally, TIGAR overexpression reduced the elevation of ATF4 target genes and attenuated ER stress-induced cell death. Notably, TIGAR co-localized and interacted with ATF4 in the nucleus, inhibiting its downstream pro-apoptotic gene transcription, consequently protecting against ischemic injury. In vitro and in vivo experiments revealed that ATF4 overexpression reversed the protective effects of TIGAR against cerebral ischemic injury. Intriguingly, our study identified the Q141/K145 residues of TIGAR, crucial for its nuclear translocation and interaction with ATF4, highlighting a novel aspect of TIGAR's function distinct from its known phosphatase activity or mitochondrial localization domains. These findings reveal a novel neuroprotective mechanism of TIGAR in regulating ER stress through ATF4-mediated signaling pathways. These insights may guide targeted therapeutic strategies to protect neuronal function and alleviate the deleterious effects of cerebral ischemic injury.Significance statement TIGAR (TP53-induced glycolysis and apoptosis regulator) is one of the downstream target genes of p53, and its encoded protein exerts Fru-2, 6-BPase activity to promote glucose metabolic flux to pentose phosphate pathway. However, the non-enzymatic function of TIGAR has been gradually discovered. Here, we demonstrate that TIGAR translocates to the nucleus to interact with ATF4 in neurons after cerebral ischemia/reperfusion induced ER stress via its Q141/K145 residues. Then TIGAR inhibits ATF4's downstream pro-apoptotic genes expression, reduces ER stress-dependent apoptosis, consequently alleviating neuronal damage. This study uncovered a novel neuroprotective mechanism of TIGAR by regulating ER stress via ATF4-mediated signaling pathway. The Q141/K145 residues of TIGAR are critical for its interaction with ATF4 and inhibition of ATF4 target genes.

Our visual percept of small differences in depth is largely informed by binocular stereopsis, the ability to decode depth from the horizontal offset between the retinal images in each eye. While multiple cortical areas are associated with stereoscopic processing, it is unclear how tuning to specific binocular disparities is organised across human visual cortex. We used 3T functional magnetic resonance imaging to generate population receptive fields in response to modulation of binocular disparity to characterise the neural tuning to disparity. We also used psychophysics to measure stereoacuity thresholds compared to backgrounds at different depths (pedestal disparity). Ten human participants (7 female) observed correlated or anticorrelated random-dot stereograms with disparity ranging from -0.3° to 0.3°, and responses were modelled as 1-dimensional tuning curves along the depth dimension. First, we demonstrate that lateral and dorsal visual areas show the greatest proportion of vertices selective for binocular disparity. Second, with binocularly correlated stimuli, we show a polynomial relationship between preferred disparity and tuning curve width, with sharply tuned disparity responses at near-zero disparities, and broader disparity tuning profiles at near or far disparities. This relationship held across visual areas and was not present for anticorrelated stimuli. Finally, the individual thresholds for psychophysical stereoacuity at the 3 different pedestal disparities were broadly related to population receptive field tuning width in area V1, suggesting a possible limit for fine stereopsis at the earliest level of cortical processing. Together, these findings point to heterogeneity of disparity processing across human visual areas, comparable to non-human primates.Significance Statement Binocular disparity arises from the horizonal separation of the two eyes and provides information for determining depth and 3D structure. We used functional magnetic resonance imaging and population receptive field mapping to measure tuning of multiple visual areas to binocular disparity in the human visual cortex. We additionally measured psychophysical thresholds for detecting binocular disparity and correlated these with the neural measures. The width of the disparity tuning was related to the preferred disparity across all visual areas. Disparity tuning widths in V1 were also related to psychophysical thresholds. These findings in the human are broadly comparable to non-human primates.

The medial pulvinar thalamic nucleus (MPu) is an evolutionary novelty of the primate thalamus, prominently expanded in humans. Piecemeal data from studies in various monkey species indicates that MPu axons reach prefrontal, inferior parietal, cingulate, insular or temporal areas; however, the precise wiring and functional logic of such brain-wide connections remain obscure. In marmoset monkeys (Callithrix jacchus) of both sexes, we visualized the axons originated from specific pulvinar domains by means of biotinylated dextranamine (BDA) microinjections and compared them across multiple cases. In addition, by injecting retrograde tracers in the cortical areas targeted by the pulvinar axons, we investigated the organization of projection cells within MPu and the existence of long-range branched axons. Specific projection motifs reveal a caudal MPu subnucleus that innervates inferior and ventral temporal areas, and a rostral MPu subnucleus that innervates temporal, ventral prefrontal, premotor, inferior posterior parietal and cingulate areas. We demonstrate numerous MPu neurons that innervate through branched axons prefrontal and parietal or prefrontal and temporal areas; other cells with different projection patterns are closely intermingled with them. Our findings support the notion that MPu is a hub of the brain-wide networks that support complex visual and social cognition, sensory-guided reaching, working memory, and attention. Moreover, the finding of long-range branching MPu axons and dense terminal arborizations suggest that MPu cells may regulate functional connectivity among high-level cortical areas at widely different spatial scales. Besides, the anatomical "ground truth" provided by our study is relevant for functional imaging and distributed network modelling studies.Significance statement The medial nucleus of the pulvinar complex is an evolutionary novelty of the primate thalamus and is uniquely expanded in humans. However, its functions are poorly understood, as data on its connections remain incomplete and fragmentary. Using high-resolution connection-labeling methods in marmoset monkeys, we mapped in full the thalamocortical axons arising from specific medial pulvinar domains and analyzed their branching patterns. Projection motifs reveal two main subnuclei, each targeting specific cortical networks. Moreover, we show that some pulvinar neurons simultaneously innervate distant prefrontal and parietal areas or prefrontal and temporal areas. Their connection patterns might allow medial pulvinar cells modulate, at different scales, functional connectivity in the cortical networks supporting object vision, social cognition, attention sensory-guided reaching and working memory.

Inhibition of GABAergic interneurons has been found to critically fine-tune the excitation-inhibition balance of the cortex. Inhibition is mediated by many connectivity motifs formed by GABAergic neurons. One such motif is the inhibition of somatostatin (SST)-expressing neurons by vasoactive intestinal polypeptide (VIP)-expressing neurons. We studied the synaptic properties of layer (L) 2/3 VIP cells onto L4 SST cells in somatosensory (S1) and visual (V1) cortices of mice of either sex using paired whole-cell patch clamp recordings, followed by morphological reconstructions. We identified strong differences in the morphological features of L4 SST cells, wherein cells in S1 fell into the non-Martinotti cell (nMC) subclass, while in V1 presented with Martinotti cell (MC)-like features. Around 40-45% of tested SST cells were inhibited by VIP cells in both cortices. While unitary connectivity properties of the VIP-to-nMC and VIP-to-MC motif were comparable, we observed stark differences in short-term plasticity. During high-frequency stimulation of both motifs, some connections showed short-term facilitation while others showed a stable response, with a fraction of VIP-to-nMC connections showing short-term depression. We thus provide evidence that VIP cells target morphological subclasses of SST cells differentially, forming cell-type specific inhibitory motifs.Significance statement Inhibitory circuits are involved in a wide variety of cortical computations. In particular, the inhibition of somatostatin-expressing (SST) neurons by vasoactive intestinal polypeptide- expressing (VIP) neurons has been well-documented in L2/3 of sensory cortices. It was recently identified that L4 SST neurons of S1 and V1 exhibit two different morphological subtypes, namely, non-Martinotti (nMC) cells in S1 and Martinotti (MC) cells in V1. We show that L2/3 VIP neurons inhibit both SST subtypes in L4 with similar dynamics. However, we also find that under high frequency stimulations, the VIP-to-nMC motif exhibits strong short-term depression, but this was not observed in VIP-to-MC motifs. Therefore, we identified morphologically distinct, inhibitory cell-type specific motifs in sensory cortices of mouse.

The conventional understanding of the cerebellum as a sole movement control center has become obsolete, given its role in various higher-order functions, including cognition, emotion, and social processing. As these functions emerge during infancy, it is logical to assume that the cerebellum's functional organization must evolve in tandem or preemptively to underpin these functions. However, the longitudinal development of the cerebellum's functional architecture during the crucial early years of infant life remains largely unexplored, highlighting a significant research gap. In this study, leveraging a large cohort of both male and female full-term (n=155) and preterm (n=67) infants, we aimed to delineate the development of within-cerebellum and cerebello-cortical functional connections during the first two years of life. Our findings highlight comprehensive functional synchronization within the neonatal cerebellum with a striking cortical projection focus on primary sensorimotor and visual cortices. While the within-cerebellum synchronization demonstrated early emergence in neonates and developmental stability during the initial two years, the cerebello-cortical projection patterns evolved dramatically, marked by specialization, shifting, and higher-order cortex integration, providing exciting evidence of the cerebellum's involvement in higher-order functions from infancy. Furthermore, preterm infants exhibited decreased cerebello-cortical connectivity compared to their full-term counterparts, suggesting potential developmental alterations. These findings collectively illustrate a dynamic growth pattern of cerebellar functional organization marked by both within-cerebellum stability and cerebellar-cortical projection plasticity with significant implications for long-term cognitive and socioemotional development.Significance Statement The cerebellum is crucial for motor and higher-order cognitive and socioemotional processes. However, the role of early cerebellar development and its cortical projections in supporting these emerging functions during the first years of life remains poorly understood. Our study, based on a large cohort of full-term and preterm infants, reveals the early and stable functional organization of the cerebellar networks from birth to two years, alongside dynamic cerebello-cortical connectivity growth, reflecting both stability and developmental plasticity. We observed a dramatic shift in cerebello-cortical projections from sensorimotor to higher-order association cortices, highlighting its role in emerging higher-order functions. Moreover, diminished growth of these connections indicates possible developmental delays in preterm infants, emphasizing the cerebellum's importance in early brain and behavioral development.

Kölliker's organ is a transient developmental structure in the mouse cochlea that undergoes significant remodeling postnatally. Utilizing an epithelial-specific conditional deletion mouse model of Prdm16 (marker and regulator of Kölliker's organ), we show that Prdm16 is required for interdental cell development, and thereby the development of the limbal domain of the tectorial membrane and its medial anchorage to the spiral limbus. Additionally, we show that Kölliker's organ is involved in normal tectorial membrane collagen fibril development and maturation. Interestingly, mesenchymal cells of the spiral limbus underneath Prdm16-deficient Kölliker's organ failed to produce interstitial matrix proteins, resulting in a hypoplastic and truncated spiral limbus, indicating a non-cell autonomous role of Prdm16 in regulating spiral mesenchymal matrix development. Single cell RNA sequencing identified differentially expressed genes in Prdm16-deficient Kölliker's organ suggesting a role for connective tissue growth factor (CTGF) downstream Prdm16 in epithelial-mesenchymal signaling involved in spiral limbus matrix deposition. Prdm16-deficient mice showed a hearing deficit, as indicated by elevated auditory brain stem response thresholds at most frequencies, consistent with the cochlear structural defects. Both sexes were studied. This work establishes Prdm16 as a deafness gene in mice through its role in regulating Kölliker's organ development. Such understanding recognizes Kölliker's organ as a developmental hub regulating multiple surrounding cochlear structures.Significance Statement In this study, we show that the Kölliker's organ functions as a developmental hub that orchestrates the development of tectorial membrane and spiral limbus during cochlear development. Utilizing a mouse model of conditional deletion of Prdm16 (marker and regulator of Kölliker's organ), we establish Prdm16's necessity for hearing in mice through its many roles during cochlear development including permitting interdental cell development and thereby the formation of the tectorial membrane limbal domain, secreting collagens essential for tectorial membrane matrix development, and signaling to the underlying mesenchyme to secrete extracellular matrix and develop the spiral limbus.

Perineuronal nets (PNNs) are a specialized extracellular matrix that surrounds certain populations of neurons, including (inhibitory) parvalbumin (PV)-expressing interneurons throughout the brain and (excitatory) CA2 pyramidal neurons in hippocampus. PNNs are thought to regulate synaptic plasticity by stabilizing synapses and as such, could regulate learning and memory. Most often, PNN functions are queried using enzymatic degradation with chondroitinase, but that approach does not differentiate PNNs on CA2 neurons from those on adjacent PV cells. To disentangle the specific roles of PNNs on CA2 pyramidal cells and PV neurons in behavior, we generated conditional knock-out mouse strains with the primary protein component of PNNs, aggrecan (Acan), deleted from either CA2 pyramidal cells (Amigo2 Acan KO) or from PV cells (PV Acan KO). Male and female animals of each strain were tested for social, fear, and spatial memory, as well as for reversal learning. We found that Amigo2 Acan KO animals, but not PV Acan KO animals, had impaired social memory and reversal learning. PV Acan KOs, but not Amigo2 Acan KOs, had impaired contextual fear memory. These findings demonstrate independent roles for PNNs on each cell type in regulating hippocampal-dependent memory. We further investigated a potential mechanism of impaired social memory in the Amigo2 Acan KO animals and found reduced input to CA2 from the supramammillary nucleus (SuM), which signals social novelty. Additionally, Amigo2 Acan KOs lacked a social novelty-related local field potential response, suggesting that CA2 PNNs may coordinate functional SuM connections and associated physiological responses to social novelty.

Neuroendocrine cells react to physical, chemical, and synaptic signals originating from tissues and the nervous system, releasing hormones that regulate various body functions beyond the synapse. Neuroendocrine cells are often embedded in complex tissues making direct tests of their activation mechanisms and signaling effects difficult to study. In the nematode worm Caenorhabditis elegans, four uterine-vulval (uv1) neuroendocrine cells sit above the vulval canal next to the egg-laying circuit, releasing tyramine and neuropeptides that feedback to inhibit egg laying. We have previously shown uv1 cells are mechanically deformed during egg laying, driving uv1 Ca²⁺ transients. However, whether egg-laying circuit activity, vulval opening, and/or egg release triggered uv1 Ca²⁺ activity was unclear. Here, we show uv1 responds directly to mechanical activation. Optogenetic vulval muscle stimulation triggers uv1 Ca²⁺ activity following muscle contraction even in sterile animals. Direct mechanical prodding with a glass probe placed against the worm cuticle triggers robust uv1 Ca²⁺ activity similar to that seen during egg laying. Direct mechanical activation of uv1 cells does not require other cells in the egg-laying circuit, synaptic or peptidergic neurotransmission, or transient receptor potential vanilloid and Piezo channels. EGL-19 L-type Ca²⁺ channels, but not P/Q/N-type or ryanodine receptor Ca²⁺ channels, promote uv1 Ca²⁺ activity following mechanical activation. L-type channels also facilitate the coordinated activation of uv1 cells across the vulva, suggesting mechanical stimulation of one uv1 cell cross-activates the other. Our findings show how neuroendocrine cells like uv1 report on the mechanics of tissue deformation and muscle contraction, facilitating feedback to local circuits to coordinate behavior.

Inhibitory control is a crucial cognitive-control ability for behavioral flexibility, which has been extensively investigated through action-stopping tasks. Multiple neurophysiological features have been proposed as 'signatures' of inhibitory control during action-stopping, though the processes indexed by these signatures are still controversially discussed. The present study aimed to disentangle these processes by comparing simple stopping situations with those in which additional action revisions were needed. Three experiments in female and male humans were performed to characterize the neurophysiological dynamics involved in action-stopping and -changing, with hypotheses derived from recently developed two-stage 'pause-then-cancel' models of inhibitory control. Both stopping and revising an action triggered an early, broad 'pause'-process, marked by frontal EEG β-frequency bursting and non-selective suppression of corticospinal excitability. However, EMG showed that motor activity was only partially inhibited by this 'pause', and that this activity could be modulated during action-revision. In line with two-stage models of inhibitory control, subsequent frontocentral EEG activity after this initial 'pause' selectively scaled depending on the required action revisions, with more activity observed for more complex revisions. This demonstrates the presence of a selective, effector-specific 'retune' phase as the second process involved in action-stopping and -revision. Together, these findings show that inhibitory control is implemented over an extended period of time and in at least two phases. We are further able to align the most commonly proposed neurophysiological signatures to these phases and show that they are differentially modulated by the complexity of action-revision.Significance Statement Inhibitory control is one of the most important control processes by which humans can regulate their behavior. Multiple neurophysiological signatures have been proposed to index inhibitory control. However, these play out on different time scales and appear to reflect different aspects of cognitive control, which are controversially debated.Recent two-stage models of inhibitory control have proposed that two phases implement the revisions of actions: 'pause' and 'retune'. Here, we provide the first empirical evidence for this proposition: Action revisions engendered a common, low-latency 'pause' process, during which motor activity is broadly suppressed. Later activity, however, distinguishes between simple stopping of actions and more complex action revisions. These findings provide novel insights into the sequential dynamics of human action control.