RESUMO
The role of postnatal experience in sculpting cortical circuitry, while long appreciated, is poorly understood at the level of cell types. We explore this in the mouse primary visual cortex (V1) using single-nucleus RNA sequencing, visual deprivation, genetics, and functional imaging. We find that vision selectively drives the specification of glutamatergic cell types in upper layers (L) (L2/3/4), while deeper-layer glutamatergic, GABAergic, and non-neuronal cell types are established prior to eye opening. L2/3 cell types form an experience-dependent spatial continuum defined by the graded expression of â¼200 genes, including regulators of cell adhesion and synapse formation. One of these genes, Igsf9b, a vision-dependent gene encoding an inhibitory synaptic cell adhesion molecule, is required for the normal development of binocular responses in L2/3. In summary, vision preferentially regulates the development of upper-layer glutamatergic cell types through the regulation of cell-type-specific gene expression programs.
Assuntos
Visão Ocular , Córtex Visual/citologia , Córtex Visual/embriologia , Animais , Animais Recém-Nascidos , Biomarcadores/metabolismo , Perfilação da Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento , Ácido Glutâmico/metabolismo , Masculino , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Camundongos Endogâmicos C57BL , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Neurônios/citologia , RNA-Seq , Transcriptoma/genética , Visão Binocular/genética , Ácido gama-Aminobutírico/metabolismoRESUMO
In spite of the high metabolic cost of cellular production, the brain contains only a fraction of the neurons generated during embryonic development. In the rodent cerebral cortex, a first wave of programmed cell death surges at embryonic stages and affects primarily progenitor cells. A second, larger wave unfolds during early postnatal development and ultimately determines the final number of cortical neurons. Programmed cell death in the developing cortex is particularly dependent on neuronal activity and unfolds in a cell-specific manner with precise temporal control. Pyramidal cells and interneurons adjust their numbers in sync, which is likely crucial for the establishment of balanced networks of excitatory and inhibitory neurons. In contrast, several other neuronal populations are almost completely eliminated through apoptosis during the first two weeks of postnatal development, highlighting the importance of programmed cell death in sculpting the mature cerebral cortex.
Assuntos
Apoptose/fisiologia , Neocórtex/citologia , Neocórtex/crescimento & desenvolvimento , Animais , Apoptose/genética , Diferenciação Celular/fisiologia , Proliferação de Células/fisiologia , Humanos , Interneurônios/citologia , Interneurônios/metabolismo , Neocórtex/metabolismo , Neuroglia/citologia , Neuroglia/metabolismo , Células Piramidais/citologia , Células Piramidais/metabolismoRESUMO
Even a transient period of hearing loss during the developmental critical period can induce long-lasting deficits in temporal and spectral perception. These perceptual deficits correlate with speech perception in humans. In gerbils, these hearing loss-induced perceptual deficits are correlated with a reduction of both ionotropic GABAA and metabotropic GABAB receptor-mediated synaptic inhibition in auditory cortex, but most research on critical period plasticity has focused on GABAA receptors. Therefore, we developed viral vectors to express proteins that would upregulate gerbil postsynaptic inhibitory receptor subunits (GABAA, Gabra1; GABAB, Gabbr1b) in pyramidal neurons, and an enzyme that mediates GABA synthesis (GAD65) presynaptically in parvalbumin-expressing interneurons. A transient period of developmental hearing loss during the auditory critical period significantly impaired perceptual performance on two auditory tasks: amplitude modulation depth detection and spectral modulation depth detection. We then tested the capacity of each vector to restore perceptual performance on these auditory tasks. While both GABA receptor vectors increased the amplitude of cortical inhibitory postsynaptic potentials, only viral expression of postsynaptic GABAB receptors improved perceptual thresholds to control levels. Similarly, presynaptic GAD65 expression improved perceptual performance on spectral modulation detection. These findings suggest that recovering performance on auditory perceptual tasks depends on GABAB receptor-dependent transmission at the auditory cortex parvalbumin to pyramidal synapse and point to potential therapeutic targets for developmental sensory disorders.
Assuntos
Córtex Auditivo , Gerbillinae , Perda Auditiva , Animais , Córtex Auditivo/metabolismo , Córtex Auditivo/fisiopatologia , Perda Auditiva/genética , Perda Auditiva/fisiopatologia , Receptores de GABA-B/metabolismo , Receptores de GABA-B/genética , Glutamato Descarboxilase/metabolismo , Glutamato Descarboxilase/genética , Receptores de GABA-A/metabolismo , Receptores de GABA-A/genética , Parvalbuminas/metabolismo , Parvalbuminas/genética , Percepção Auditiva/fisiologia , Células Piramidais/metabolismo , Células Piramidais/fisiologia , Vetores Genéticos/genéticaRESUMO
Congenital single-sided deafness (SSD) leads to an aural preference syndrome that is characterized by overrepresentation of the hearing ear in the auditory system. Cochlear implantation (CI) of the deaf ear is an effective treatment for SSD. However, the newly introduced auditory input in congenital SSD often does not reach expectations in late-implanted CI recipients with respect to binaural hearing and speech perception. In a previous study, a reduction of the interaural time difference (ITD) sensitivity has been shown in unilaterally congenitally deaf cats (uCDCs). In the present study, we focused on the interaural level difference (ILD) processing in the primary auditory cortex. The uCDC group was compared with hearing cats (HCs) and bilaterally congenitally deaf cats (CDCs). The ILD representation was reorganized, replacing the preference for the contralateral ear with a preference for the hearing ear, regardless of the cortical hemisphere. In accordance with the previous study, uCDCs were less sensitive to interaural time differences than HCs, resulting in unmodulated ITD responses, thus lacking directional information. Such incongruent ITDs and ILDs cannot be integrated for binaural sound source localization. In normal hearing, the predominant effect of each ear is excitation of the auditory cortex in the contralateral cortical hemisphere and inhibition in the ipsilateral hemisphere. In SSD, however, auditory pathways reorganized such that the hearing ear produced greater excitation in both cortical hemispheres and the deaf ear produced weaker excitation and preserved inhibition in both cortical hemispheres.
Assuntos
Córtex Auditivo , Implante Coclear , Sinais (Psicologia) , Perda Auditiva Unilateral , Localização de Som , Gatos , Animais , Localização de Som/fisiologia , Perda Auditiva Unilateral/fisiopatologia , Implante Coclear/métodos , Córtex Auditivo/fisiopatologia , Feminino , Masculino , Estimulação Acústica/métodos , Lateralidade Funcional/fisiologia , Surdez/fisiopatologia , Surdez/congênito , Surdez/cirurgiaRESUMO
Neural activity influences every aspect of nervous system development. In olfactory systems, sensory neurons expressing the same odorant receptor project their axons to stereotypically positioned glomeruli, forming a spatial map of odorant receptors in the olfactory bulb. As individual odors activate unique combinations of glomeruli, this map forms the basis for encoding olfactory information. The establishment of this stereotypical olfactory map requires coordinated regulation of axon guidance molecules instructed by spontaneous activity. Recent studies show that sensory experiences also modify innervation patterns in the olfactory bulb, especially during a critical period of the olfactory system development. This review examines evidence in the field to suggest potential mechanisms by which various aspects of neural activity regulate axon targeting. We also discuss the precise functions served by neural plasticity during the critical period.
Assuntos
Neurônios Receptores Olfatórios , Receptores Odorantes , Animais , Neurônios Receptores Olfatórios/metabolismo , Bulbo Olfatório/fisiologia , Receptores Odorantes/genética , Receptores Odorantes/metabolismo , Axônios/metabolismo , MamíferosRESUMO
Drought is a major abiotic stress reducing maize (Zea mays) yield worldwide especially before and during silking. The mechanism underlying drought tolerance in maize and the roles of different organs have not been elucidated. Hence, we conducted field trials under pre-silking drought conditions using two maize genotypes: FM985 (drought-tolerant) and ZD958 (drought-sensitive). The two genotypes did not differ in plant height, grain number, and yield under control conditions. However, the grain number per ear and the yield of FM985 were 38.1 and 35.1% higher and plants were 17.6% shorter than ZD958 under drought conditions. More 13 C photosynthates were transported to the ear in FM985 than in ZD958, which increased floret fertility and grain number. The number of differentially expressed genes was much higher in stem than in other organs. Stem-ear interactions are key determinants of drought tolerance, in which expression of genes related to abscisic acid, lignin, and flavonoid biosynthesis and carbon metabolism in the stem was induced by drought, which inhibited stem elongation and promoted assimilate allocation to the ear in FM985. In comparison with ZD958, the activities of trehalose 6-phosphate phosphatase and sucrose non-fermentation-associated kinase 1 were higher in the stem and lower in the kernel of FM985, which facilitated kernel formation. These results reveal that, beyond the ear response, stem elongation is involved in the whole process of drought tolerance before silking. Abscisic acid together with trehalose 6-phosphate, lignin, and flavonoid suppresses stem elongation and allocates assimilates into the ear, providing a novel and systematic regulatory pathway for drought tolerance in maize.
Assuntos
Ácido Abscísico , Resistência à Seca , Ácido Abscísico/metabolismo , Zea mays/metabolismo , Lignina/metabolismo , Flavonoides/metabolismo , Trealose/metabolismo , Grão Comestível , Secas , Fosfatos/metabolismo , Estresse FisiológicoRESUMO
The hypothesis that impoverished language experience affects complex sentence structure development around the end of early childhood was tested using a fully randomized, sentence-to-picture matching study in American Sign Language (ASL). The participants were ASL signers who had impoverished or typical access to language in early childhood. Deaf signers whose access to language was highly impoverished in early childhood (N = 11) primarily comprehended structures consisting of a single verb and argument (Subject or Object), agreeing verbs, and the spatial relation or path of semantic classifiers. They showed difficulty comprehending more complex sentence structures involving dual lexical arguments or multiple verbs. As predicted, participants with typical language access in early childhood, deaf native signers (N = 17) or hearing second-language learners (N = 10), comprehended the range of 12 ASL sentence structures, independent of the subjective iconicity or frequency of the stimulus lexical items, or length of ASL experience and performance on non-verbal cognitive tasks. The results show that language experience in early childhood is necessary for the development of complex syntax. RESEARCH HIGHLIGHTS: Previous research with deaf signers suggests an inflection point around the end of early childhood for sentence structure development. Deaf signers who experienced impoverished language until the age of 9 or older comprehend several basic sentence structures but few complex structures. Language experience in early childhood is necessary for the development of complex sentence structure.
Assuntos
Surdez , Idioma , Pré-Escolar , Humanos , Língua de Sinais , Semântica , AudiçãoRESUMO
Children achieve better long-term language outcomes than adults. However, it remains unclear whether children actually learn language more quickly than adults during real-time exposure to input-indicative of true superior language learning abilities-or whether this advantage stems from other factors. To examine this issue, we compared the rate at which children (8-10 years) and adults extracted a novel, hidden linguistic rule, in which novel articles probabilistically predicted the animacy of associated nouns (e.g., "gi lion"). Participants categorized these two-word phrases according to a second, explicitly instructed rule over two sessions, separated by an overnight delay. Both children and adults successfully learned the hidden animacy rule through mere exposure to the phrases, showing slower response times and decreased accuracy to occasional phrases that violated the rule. Critically, sensitivity to the hidden rule emerged much more quickly in children than adults; children showed a processing cost for violation trials from very early on in learning, whereas adults did not show reliable sensitivity to the rule until the second session. Children also showed superior generalization of the hidden animacy rule when asked to classify nonword trials (e.g., "gi badupi") according to the hidden animacy rule. Children and adults showed similar retention of the hidden rule over the delay period. These results provide insight into the nature of the critical period for language, suggesting that children have a true advantage over adults in the rate of implicit language learning. Relative to adults, children more rapidly extract hidden linguistic structures during real-time language exposure. RESEARCH HIGHLIGHTS: Children and adults both succeeded in implicitly learning a novel, uninstructed linguistic rule, based solely on exposure to input. Children learned the novel linguistic rules much more quickly than adults. Children showed better generalization performance than adults when asked to apply the novel rule to nonsense words without semantic content. Results provide insight into the nature of critical period effects in language, indicating that children have an advantage over adults in real-time language learning.
Assuntos
Desenvolvimento da Linguagem , Linguística , Humanos , Criança , Adulto , Masculino , Feminino , Tempo de Reação/fisiologia , Aprendizagem , Adulto JovemRESUMO
Despite previous agreement of the absence of cortical column structure in the rodent visual cortex, we have recently revealed a presence of ocular dominance columns (ODCs) in the primary visual cortex (V1) of adult Long-Evans rats. In this study, we deepened understanding of characteristics of rat ODCs. We found that this structure was conserved in Brown Norway rats, but not in albino rats; therefore, it could be a structure generally present in pigmented wild rats. Activity-dependent gene expression indicated that maturation of eye-dominant patches takes more than 2 weeks after eye-opening, and this process is visual experience dependent. Monocular deprivation during classical critical period strongly influenced size of ODCs, shifting ocular dominance from the deprived eye to the opened eye. On the other hand, transneuronal anterograde tracer showed a presence of eye-dominant patchy innervation from the ipsilateral V1 even before eye-opening, suggesting the presence of visual activity-independent genetic components of developing ODCs. Pigmented C57BL/6J mice also showed minor clusters of ocular dominance neurons. These results provide insights into how visual experience-dependent and experience-independent components both contribute to develop cortical columns during early postnatal stages, and indicate that rats and mice can be excellent models to study them.
Assuntos
Dominância Ocular , Córtex Visual , Animais , Ratos , Camundongos , Ratos Long-Evans , Camundongos Endogâmicos C57BL , Córtex Visual/fisiologia , Neurônios/fisiologiaRESUMO
Restoration of human brain function after injury is a signal challenge for translational neuroscience. Rodent stroke recovery studies identify an optimal or sensitive period for intensive motor training after stroke: near-full recovery is attained if task-specific motor training occurs during this sensitive window. We extended these findings to adult humans with stroke in a randomized controlled trial applying the essential elements of rodent motor training paradigms to humans. Stroke patients were adaptively randomized to begin 20 extra hours of self-selected, task-specific motor therapy at ≤30 d (acute), 2 to 3 mo (subacute), or ≥6 mo (chronic) after stroke, compared with controls receiving standard motor rehabilitation. Upper extremity (UE) impairment assessed by the Action Research Arm Test (ARAT) was measured at up to five time points. The primary outcome measure was ARAT recovery over 1 y after stroke. By 1 y we found significantly increased UE motor function in the subacute group compared with controls (ARAT difference = +6.87 ± 2.63, P = 0.009). The acute group compared with controls showed smaller but significant improvement (ARAT difference = +5.25 ± 2.59 points, P = 0.043). The chronic group showed no significant improvement compared with controls (ARAT = +2.41 ± 2.25, P = 0.29). Thus task-specific motor intervention was most effective within the first 2 to 3 mo after stroke. The similarity to rodent model treatment outcomes suggests that other rodent findings may be translatable to human brain recovery. These results provide empirical evidence of a sensitive period for motor recovery in humans.
Assuntos
Atividade Motora/fisiologia , Recuperação de Função Fisiológica , Reabilitação do Acidente Vascular Cerebral/métodos , Acidente Vascular Cerebral/terapia , Idoso , Estudos de Casos e Controles , Feminino , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Prognóstico , Estudos ProspectivosRESUMO
The cerebellum has been increasingly implicated in autism spectrum disorder (ASD) with many ASD-linked genes impacting both cerebellar function and development. However, the precise timing and critical periods of when abnormal cerebellar neurodevelopment contributes to ASD-relevant behaviors remains poorly understood. In this study, we identify a critical period for the development of ASD-relevant behaviors in a cerebellar male mouse model of tuberous sclerosis complex (TSC), by using the mechanistic target of rapamycin (mTOR) inhibitor, rapamycin, to pharmacologically inhibit dysregulated downstream signaling. We find independent critical periods during which abnormal ASD-relevant behaviors develop for the two core ASD diagnostic criteria, social impairments and behavioral flexibility, and delineate an anatomic, physiological, and behavioral framework. These findings not only further our understanding of the genetic mechanisms underlying the timing of ASD-relevant behaviors but also have the capacity to inform potential therapies to optimize treatment interventions.SIGNIFICANCE STATEMENT No targeted treatments currently exist for autism spectrum disorder (ASD). This complex developmental disorder has established links to genetic and circuit aberrations, yet the precise timing and coordination of these underlying mechanisms that contribute to the spectrum of physiological and behavioral abnormalities remains unclear. Cerebellar pathology is consistently seen in ASD individuals; therefore, we sought to identify the specific windows for cerebellar involvement in the development of ASD-relevant behaviors. Using pharmacologic treatment paradigms, we outline distinct critical periods of developmental vulnerability for ASD-relevant social and inflexible behaviors. From this study, we posit a refined window of time during which ASD symptoms develop that will inform therapeutic timing.
Assuntos
Transtorno do Espectro Autista , Transtorno Autístico , Esclerose Tuberosa , Animais , Cerebelo , Masculino , Camundongos , Comportamento Social , Esclerose Tuberosa/patologiaRESUMO
Sensory experience during a critical period alters sensory cortical responses and organization. We find that the earliest sound-driven activity in the mouse auditory cortex (ACX) starts before ear-canal opening (ECO). The effects of auditory experience before ECO on ACX development are unknown. We find that in mouse ACX subplate neurons (SPNs), crucial in thalamocortical maturation, respond to sounds before ECO showing oddball selectivity. Before ECO, SPNs are more selective to oddball sounds in auditory streams than thalamo-recipient layer 4 (L4) neurons and not after ECO. We hypothesize that SPN's oddball selectivity can direct the development of L4 responses before ECO. Exposing mice, of either sex, before ECO to a rarely occurring tone in a stream of another tone occurring frequently leads to strengthening the adult cortical representation of the rare tone, but not that of the frequent tone. Results of control exposure experiments at multiple developmental windows that also use only a single tone corroborate the observations. We further explain the strengthening of deviant inputs before ECO and not after ECO using a binary network model mimicking the hierarchical structure of subplate and L4 neurons and response properties derived from our data, with synapses following Hebbian spike time-dependent plasticity learning rule. Information-theoretic analysis with sparse coding assumptions also predicts the observations. Thus, relatively salient low probability sounds in the earliest auditory environment cause long-term changes in the ACX.SIGNIFICANCE STATEMENT Early auditory experience can change the organization and responses of the auditory cortex in adulthood. However, little is known about how auditory experience at prenatal ages changes neural circuits and response properties. In mice at equivalent early developmental stages, we find that auditory experience of a particular kind, with a less frequently occurring sound in a stream of another sound, alters adult cortical responsiveness, specifically of the less frequent sound. However, at the previously known critical period of development, the opposite is observed, where the more frequent sound's representation is strengthened in the adult compared with the less frequent sound. We thus show that a specific type of auditory environment can influence adult auditory processing at the earliest ages.
Assuntos
Córtex Auditivo , Estimulação Acústica/métodos , Animais , Córtex Auditivo/fisiologia , Percepção Auditiva/fisiologia , Camundongos , Neurônios/fisiologia , Som , Sinapses/fisiologiaRESUMO
Cortical layer 1 (L1) contains a diverse population of interneurons that can modulate processing in superficial cortical layers, but the intracortical sources of synaptic input to these neurons and how these inputs change over development and with sensory experience is unknown. We here investigated the changing intracortical connectivity to L1 in the primary auditory cortex (A1) of mice of both sexes in in vitro slices across development using laser-scanning photostimulation. Before postnatal day (P)10, L1 cells receive excitatory input from within L1, L2/3, L4, and L5/6 as well as from subplate. Excitatory inputs from all layers increase, especially from L4, and peak during P10-P16, around the peak of the critical period for tonotopy. Inhibitory inputs followed a similar pattern. Functional circuit diversity in L1 emerges after P16. In adults, L1 neurons receive ascending inputs from L2/3 and L5/6, but only few inputs from L4. The transient hyperconnectivity from deep layers but not L2/3 is absent in deaf mice. Our results demonstrate that deep excitatory and superficial inhibitory circuits are tightly linked in early development and might provide a functional scaffold for the layers in between. These results suggest that early thalamically driven spontaneous and sensory activity in subplate can be relayed to L1 from the earliest ages on and shape L1 connectivity from deep layers. Our results also reveal a period of high transient columnar hyperconnectivity after ear opening coinciding with the critical period, suggesting that circuits originating in deep layers might play a key role in this process.SIGNIFICANCE STATEMENT L1 contains a diverse population of interneurons that can modulate processing in superficial cortical layers but the sources of synaptic input to these neurons and how these inputs change over development is unknown. We found that during the critical period a large fraction of excitatory inputs to L1 originated in L5/6 and the cortical subplate. This hyperconnectivity is absent in deaf mice. Our results directly demonstrate that deep excitatory and superficial inhibitory circuits are tightly linked in early development and might provide a functional scaffold for the layers in between.
Assuntos
Período Crítico Psicológico , Neurônios , Animais , Feminino , Interneurônios/fisiologia , Masculino , Camundongos , Neurônios/fisiologiaRESUMO
Reproductive behaviors are sexually differentiated: for example, male rodents show mounting behavior, while females in estrus show lordosis behavior as sex-specific sexual behaviors. Kisspeptin neurons govern reproductive function via direct stimulation of gonadotropin-releasing hormone (GnRH) and subsequent gonadotropin release for gonadal steroidogenesis in mammals. First, we discuss the role of hypothalamic kisspeptin neurons as an indispensable regulator of sexual behavior by stimulating the synthesis of gonadal steroids, which exert "activational effects" on the behavior in adulthood. Second, we discuss the central role of kisspeptin neurons that are directly involved in neural circuits controlling sexual behavior in adulthood. We then focused on the role of perinatal hypothalamic kisspeptin neurons in the induction of perinatal testosterone secretion for its "organizational effects" on masculinization/defeminization of the male brain in rodents during a critical period. We subsequently concluded that kisspeptin neurons are key players in bridging the endocrine system and sexual behavior in mammals.
Assuntos
Hormônio Liberador de Gonadotropina , Kisspeptinas , Animais , Sistema Endócrino , Feminino , Masculino , Mamíferos , Neurônios , Gravidez , Receptores de Kisspeptina-1RESUMO
In the present review, we discuss how the evolution of oxytocin and vasopressin from a single ancestor peptide after gene duplication has stimulated the development of the vertebrate social brain. Separate production sites became possible with a hypothalamic development, which, interestingly, is triggered by the same transcription factors that underlie the development of various subcortical regions where vasopressin and oxytocin receptors are adjacently expressed and which are connected by inhibitory circuits. The opposite modulation of their output by vasopressin and oxytocin could thus create a dynamic equilibrium for rapid responsiveness to external stimuli. At the level of the individual, nurturing early in life can long-lastingly program oxytocin signaling, maintaining a capability of learning and sensitivity to external stimuli that contributes to development of social behavior in adulthood. Oxytocin and vasopressin are thus important for the development of a vertebrate brain that supports bonding between individuals and building of an interactive community.
Assuntos
Tonsila do Cerebelo/metabolismo , Tonsila do Cerebelo/fisiologia , Ocitocina/metabolismo , Comportamento Social , Vasopressinas/metabolismo , Animais , Encéfalo/crescimento & desenvolvimento , Epigênese Genética/genética , Epigênese Genética/fisiologia , Humanos , Ocitocina/genética , Receptores de Ocitocina/metabolismo , Receptores de Vasopressinas/metabolismo , Vasopressinas/genéticaRESUMO
Concurrent, distribution-wide abundance declines of some Pacific salmon species, including Chinook salmon (Oncorhynchus tshawytscha), highlights the need to understand how vulnerability at different life stages to climate stressors affects population dynamics and fisheries sustainability. Yukon River Chinook salmon stocks are among the largest subarctic populations, near the northernmost extent of the species range. Existing research suggests that Yukon River Chinook salmon population dynamics are largely driven by factors occurring between the adult spawner life stage and their offspring's first summer at sea (second year post-hatching). However, specific mechanisms sustaining chronic poor productivity are unknown, and there is a tremendous sense of urgency to understand causes, as declines of these stocks have taken a serious toll on commercial, recreational, and indigenous subsistence fisheries. Therefore, we leveraged multiple existing datasets spanning parent and juvenile stages of life history in freshwater and marine habitats. We analyzed environmental data in association with the production of offspring that survive to the marine juvenile stage (juveniles per spawner). These analyses suggest more than 45% of the variability in the production of juvenile Chinook salmon is associated with river temperatures or water discharge levels during the parent spawning migration. Over the past two decades, parents that experienced warmer water temperatures and lower discharge in the mainstem Yukon River produced fewer juveniles per spawning adult. We propose the adult spawner life stage as a critical period regulating population dynamics. We also propose a conceptual model that can explain associations between population dynamics and climate stressors using independent data focused on marine nutrition and freshwater heat stress. It is sobering to consider that some of the northernmost Pacific salmon habitats may already be unfavorable to these cold-water species. Our findings have immediate implications, given the common assumption that northern ranges of Pacific salmon offer refugia from climate stressors.
Assuntos
Pesqueiros , Salmão , Animais , Salmão/fisiologia , Dinâmica Populacional , Rios , Água , Mudança ClimáticaRESUMO
Between the onset of the critical period of mouse primary visual cortex and eye opening at postnatal day 14 is a complex process and that is vital for the cognitive function of vision. The onset of the critical period of mouse primary visual cortex involves changes of the intrinsic firing property of each neuron and short term plasticity of synapses. In order to investigate the functional role of each factor in regulating the circuit firing activity during the critical period plasticity, we adopted the Markram's model for short term plasticity and Wilson's model for intrinsic neuron firing activity, and construct a microcircuit for mouse visual cortex layer IV based on the connection probabilities from experimental results. Our results indicate that, during CP development, the most critical factors that regulate the firing pattern of microcircuit is the short term plasticity of the synapse from PC to PV and SST interneurons, which upregulates the PV interneuron firing and produces new balance between excitation and inhibition; the intrinsic firing activity of PC and PV during development downregulates the firing frequency of the circuits. In addition, we have investigated the function of feedforward excitatory thalamic-cortical projection to PC and PV interneuron during CP, and found that neural firing activity largely depends on the TC input and the results are similar to the local circuit with minor differences. We conclude that the short term plasticity development during critical period plays a crucial role in regulating the circuit behavior.
Assuntos
Modelos Neurológicos , Córtex Visual , Camundongos , Animais , Plasticidade Neuronal/fisiologia , Neurônios , Interneurônios/fisiologia , Córtex Visual/fisiologiaRESUMO
In many taxa, the subsocial route is considered the main pathway to permanent sociality, but the relative contribution of offspring interactions and parental care to the maintenance of cohesion and tolerance at advanced developmental stages remains poorly studied. Spiders are relevant models for this question because they all show a transient gregarious phase before dispersal, and the transition to permanent sociality, which concerns approximately 20 of the â¼50,000 species, is assumed to rely on the subsocial route. Using spiderlings of the solitary species Agelena labyrinthica, we manipulated the social context to demonstrate that tolerance in aggressive juveniles can be restored when exposed to siblings after moulting. We propose that moulting can reopen closed critical periods and renew the imprinting to social cues and thus lead to the reacquisition of tolerance. Our study highlights the critical role of contacts between juveniles in the expression of tolerance, which opens novel avenues for understanding social transitions.
Assuntos
Muda , Aranhas , Animais , Comportamento Social , Agressão , Sinais (Psicologia)RESUMO
In early childhood, the human brain goes through a period of tuning to native speech sounds but retains remarkable flexibility, allowing the learning of new languages throughout life. However, little is known about the stability over time of early neural specialization for speech and its influence on the formation of novel language representations. Here, we provide evidence that early international adoptees, who lose contact with their native language environment after adoption, retain enhanced sensitivity to a native lexical tone contrast more than 15 years after being adopted to Sweden from China, in the absence of any pretest familiarization with the stimuli. Changes in oscillatory brain activity showed how adoptees resort to inhibiting the processing of defunct phonological representations, rather than forgetting or replacing them with new ones. Furthermore, neurophysiological responses to native and nonnative contrasts were not negatively correlated, suggesting that native language retention does not interfere with the acquisition of adoptive phonology acquisition. These results suggest that early language experience provides strikingly resilient specialization for speech which is compensated for through inhibitory control mechanisms as learning conditions change later in life.
Assuntos
Percepção da Fala , Encéfalo/fisiologia , Pré-Escolar , Humanos , Idioma , Aprendizagem , Fonética , Fala , Percepção da Fala/fisiologiaRESUMO
Development and maturation in cortical networks depend on neuronal activity. For stabilization and pruning of connections, synchronized oscillations play a crucial role. A fundamental mechanism that enables coordinated activity during brain functioning is formed of synchronized neuronal oscillations in low- (delta and theta) and high- (gamma) frequency bands. The relationship between neural synchrony, cognition, and the perceptual process has been widely studied, but any possible role of neural synchrony in amblyopia has been less explored. We hypothesized that monocular deprivation (MD) during early postnatal life would lead to changes in neuronal activity that would be demonstrated by changes in phase-amplitude coupling (PAC) and altered power in specific oscillatory frequency. Our results demonstrate that functional connectivity in the visual cortex is altered by MD during adolescence. The amplitude of high-frequency oscillations is modulated by the phase of low-frequency oscillations. Demonstration of enhanced delta-gamma and theta-gamma PAC indicates that our results are relevant for a broad range of nested oscillatory markers. These markers are inherent to neuronal processing and are consistent with the hypothesized increase in the intrinsic coupling that arises from neural oscillatory phase alignment. Our results reveal distinct frequency bands exhibit altered power and coherence variations modulated by experience-driven plasticity.