Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 1.733
Filtrar
1.
Nat Commun ; 12(1): 4911, 2021 08 13.
Artigo em Inglês | MEDLINE | ID: mdl-34389710

RESUMO

The mammalian sensory neocortex consists of hierarchically organized areas reciprocally connected via feedforward (FF) and feedback (FB) circuits. Several theories of hierarchical computation ascribe the bulk of the computational work of the cortex to looped FF-FB circuits between pairs of cortical areas. However, whether such corticocortical loops exist remains unclear. In higher mammals, individual FF-projection neurons send afferents almost exclusively to a single higher-level area. However, it is unclear whether FB-projection neurons show similar area-specificity, and whether they influence FF-projection neurons directly or indirectly. Using viral-mediated monosynaptic circuit tracing in macaque primary visual cortex (V1), we show that V1 neurons sending FF projections to area V2 receive monosynaptic FB inputs from V2, but not other V1-projecting areas. We also find monosynaptic FB-to-FB neuron contacts as a second motif of FB connectivity. Our results support the existence of FF-FB loops in primate cortex, and suggest that FB can rapidly and selectively influence the activity of incoming FF signals.


Assuntos
Biorretroalimentação Psicológica/fisiologia , Macaca fascicularis/fisiologia , Neurônios/fisiologia , Córtex Visual/fisiologia , Vias Visuais/fisiologia , Animais , Feminino , Corpos Geniculados/citologia , Corpos Geniculados/fisiologia , Modelos Neurológicos , Reflexo Monosináptico/fisiologia , Córtex Visual/citologia
2.
Neuron ; 109(15): 2457-2468.e12, 2021 08 04.
Artigo em Inglês | MEDLINE | ID: mdl-34146468

RESUMO

Segregation of retinal ganglion cell (RGC) axons by type and eye of origin is considered a hallmark of dorsal lateral geniculate nucleus (dLGN) structure. However, recent anatomical studies have shown that neurons in mouse dLGN receive input from multiple RGC types of both retinae. Whether convergent input leads to relevant functional interactions is unclear. We studied functional eye-specific retinogeniculate convergence using dual-color optogenetics in vitro. dLGN neurons were strongly dominated by input from one eye. Most neurons received detectable input from the non-dominant eye, but this input was weak, with a prominently reduced AMPAR:NMDAR ratio. Consistent with this, only a small fraction of thalamocortical neurons was binocular in vivo across visual stimuli and cortical projection layers. Anatomical overlap between RGC axons and dLGN neuron dendrites alone did not explain the strong bias toward monocularity. We conclude that functional eye-specific input selection and refinement limit convergent interactions in dLGN, favoring monocularity.


Assuntos
Lateralidade Funcional/fisiologia , Corpos Geniculados/citologia , Células Ganglionares da Retina/citologia , Visão Binocular/fisiologia , Vias Visuais/citologia , Animais , Corpos Geniculados/fisiologia , Camundongos , Células Ganglionares da Retina/fisiologia , Vias Visuais/fisiologia
3.
Nat Commun ; 12(1): 2438, 2021 04 26.
Artigo em Inglês | MEDLINE | ID: mdl-33903596

RESUMO

Cortical and limbic brain areas are regarded as centres for learning. However, how thalamic sensory relays participate in plasticity upon associative learning, yet support stable long-term sensory coding remains unknown. Using a miniature microscope imaging approach, we monitor the activity of populations of auditory thalamus (medial geniculate body) neurons in freely moving mice upon fear conditioning. We find that single cells exhibit mixed selectivity and heterogeneous plasticity patterns to auditory and aversive stimuli upon learning, which is conserved in amygdala-projecting medial geniculate body neurons. Activity in auditory thalamus to amygdala-projecting neurons stabilizes single cell plasticity in the total medial geniculate body population and is necessary for fear memory consolidation. In contrast to individual cells, population level encoding of auditory stimuli remained stable across days. Our data identifies auditory thalamus as a site for complex neuronal plasticity in fear learning upstream of the amygdala that is in an ideal position to drive plasticity in cortical and limbic brain areas. These findings suggest that medial geniculate body's role goes beyond a sole relay function by balancing experience-dependent, diverse single cell plasticity with consistent ensemble level representations of the sensory environment to support stable auditory perception with minimal affective bias.


Assuntos
Vias Auditivas/fisiologia , Plasticidade Celular/fisiologia , Aprendizagem/fisiologia , Plasticidade Neuronal/fisiologia , Tálamo/fisiologia , Estimulação Acústica , Tonsila do Cerebelo/citologia , Tonsila do Cerebelo/fisiologia , Animais , Percepção Auditiva/fisiologia , Condicionamento Clássico/fisiologia , Medo/fisiologia , Corpos Geniculados/citologia , Corpos Geniculados/fisiologia , Camundongos Endogâmicos C57BL , Neurônios/fisiologia , Tálamo/citologia
4.
PLoS Comput Biol ; 17(3): e1007957, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33651790

RESUMO

There are two distinct classes of cells in the primary visual cortex (V1): simple cells and complex cells. One defining feature of complex cells is their spatial phase invariance; they respond strongly to oriented grating stimuli with a preferred orientation but with a wide range of spatial phases. A classical model of complete spatial phase invariance in complex cells is the energy model, in which the responses are the sum of the squared outputs of two linear spatially phase-shifted filters. However, recent experimental studies have shown that complex cells have a diverse range of spatial phase invariance and only a subset can be characterized by the energy model. While several models have been proposed to explain how complex cells could learn to be selective to orientation but invariant to spatial phase, most existing models overlook many biologically important details. We propose a biologically plausible model for complex cells that learns to pool inputs from simple cells based on the presentation of natural scene stimuli. The model is a three-layer network with rate-based neurons that describes the activities of LGN cells (layer 1), V1 simple cells (layer 2), and V1 complex cells (layer 3). The first two layers implement a recently proposed simple cell model that is biologically plausible and accounts for many experimental phenomena. The neural dynamics of the complex cells is modeled as the integration of simple cells inputs along with response normalization. Connections between LGN and simple cells are learned using Hebbian and anti-Hebbian plasticity. Connections between simple and complex cells are learned using a modified version of the Bienenstock, Cooper, and Munro (BCM) rule. Our results demonstrate that the learning rule can describe a diversity of complex cells, similar to those observed experimentally.


Assuntos
Aprendizagem , Neurônios/fisiologia , Córtex Visual/fisiologia , Animais , Comunicação Celular , Corpos Geniculados/citologia , Corpos Geniculados/fisiologia , Modelos Neurológicos , Plasticidade Neuronal , Estimulação Luminosa/métodos , Córtex Visual/citologia
5.
Elife ; 92020 12 08.
Artigo em Inglês | MEDLINE | ID: mdl-33289630

RESUMO

Some cortical neurons receive highly selective thalamocortical (TC) input, but others do not. Here, we examine connectivity of single thalamic neurons (lateral geniculate nucleus, LGN) onto putative fast-spike inhibitory interneurons in layer 4 of rabbit visual cortex. We show that three 'rules' regulate this connectivity. These rules concern: (1) the precision of retinotopic alignment, (2) the amplitude of the postsynaptic local field potential elicited near the interneuron by spikes of the LGN neuron, and (3) the interneuron's response latency to strong, synchronous LGN input. We found that virtually all first-order fast-spike interneurons receive input from nearly all LGN axons that synapse nearby, regardless of their visual response properties. This was not the case for neighboring regular-spiking neurons. We conclude that profuse and highly promiscuous TC inputs to layer-4 fast-spike inhibitory interneurons generate response properties that are well-suited to mediate a fast, sensitive, and broadly tuned feed-forward inhibition of visual cortical excitatory neurons.


Assuntos
Potenciais de Ação/fisiologia , Corpos Geniculados/citologia , Interneurônios/fisiologia , Córtex Visual/fisiologia , Percepção Visual/fisiologia , Animais , Vias Neurais/fisiologia , Neurônios/fisiologia , Estimulação Luminosa , Coelhos , Transmissão Sináptica/fisiologia
6.
PLoS One ; 15(7): e0236760, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32726372

RESUMO

The neural mechanisms underlying forward suppression in the auditory cortex remain a puzzle. Little attention is paid to thalamic contribution despite the important fact that the thalamus gates upstreaming information to the auditory cortex. This study compared the time courses of forward suppression in the auditory thalamus, thalamocortical inputs and cortex using the two-tone stimulus paradigm. The preceding and succeeding tones were 20-ms long. Their frequency and amplitude were set at the characteristic frequency and 20 dB above the minimum threshold of given neurons, respectively. In the ventral division of the medial geniculate body of the thalamus, we found that the duration of complete forward suppression was about 75 ms and the duration of partial suppression was from 75 ms to about 300 ms after the onset of the preceding tone. We also found that during the partial suppression period, the responses to the succeeding tone were further suppressed in the primary auditory cortex. The forward suppression of thalamocortical field excitatory postsynaptic potentials was between those of thalamic and cortical neurons but much closer to that of thalamic ones. Our results indicate that early suppression in the cortex could result from complete suppression in the thalamus whereas later suppression may involve thalamocortical and intracortical circuitry. This suggests that the complete suppression that occurs in the thalamus provides the cortex with a "silence" window that could potentially benefit cortical processing and/or perception of the information carried by the preceding sound.


Assuntos
Córtex Auditivo/fisiologia , Potenciais Pós-Sinápticos Inibidores , Tálamo/fisiologia , Animais , Córtex Auditivo/citologia , Potenciais Pós-Sinápticos Excitadores , Feminino , Corpos Geniculados/citologia , Corpos Geniculados/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Neurônios/citologia , Tálamo/citologia
7.
PLoS One ; 15(4): e0232451, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32353050

RESUMO

Numerous neuronal properties including the synaptic vesicle release process, neurotransmitter receptor complement, and postsynaptic ion channels are involved in transforming synaptic inputs into postsynaptic spiking. Temperature is a significant influencer of neuronal function and synaptic integration. Changing temperature can affect neuronal physiology in a diversity of ways depending on how it affects different members of the cell's ion channel complement. Temperature's effects on neuronal function are critical for pathological states such as fever, which can trigger seizure activity, but are also important in interpreting and comparing results of experiments conducted at room vs physiological temperature. The goal of this study was to examine the influence of temperature on synaptic properties and ion channel function in thalamocortical (TC) relay neurons in acute brain slices of the dorsal lateral geniculate nucleus, a key synaptic target of retinal ganglion cells in the thalamus. Warming the superfusate in patch clamp experiments with acutely-prepared brain slices led to an overall inhibition of synaptically-driven spiking behavior in TC neurons in response to a retinal ganglion cell spike train. Further study revealed that this was associated with an increase in presynaptic synaptic vesicle release probability and synaptic depression and altered passive and active membrane properties. Additionally, warming the superfusate triggered activation of an inwardly rectifying potassium current and altered the voltage-dependence of voltage-gated Na+ currents and T-type calcium currents. This study highlights the importance of careful temperature control in ex vivo physiological experiments and illustrates how numerous properties such as synaptic inputs, active conductances, and passive membrane properties converge to determine spike output.


Assuntos
Corpos Geniculados/fisiologia , Temperatura Alta/efeitos adversos , Optogenética/métodos , Terminações Pré-Sinápticas/fisiologia , Células Ganglionares da Retina/fisiologia , Potenciais de Ação/fisiologia , Animais , Canais de Cálcio Tipo T/metabolismo , Feminino , Corpos Geniculados/citologia , Masculino , Camundongos , Técnicas de Patch-Clamp , Canais de Potássio Corretores do Fluxo de Internalização/metabolismo , Transmissão Sináptica/fisiologia , Canais de Sódio Disparados por Voltagem/metabolismo
8.
Nature ; 581(7807): 194-198, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32404998

RESUMO

Daily changes in light and food availability are major time cues that influence circadian timing1. However, little is known about the circuits that integrate these time cues to drive a coherent circadian output1-3. Here we investigate whether retinal inputs modulate entrainment to nonphotic cues such as time-restricted feeding. Photic information is relayed to the suprachiasmatic nucleus (SCN)-the central circadian pacemaker-and the intergeniculate leaflet (IGL) through intrinsically photosensitive retinal ganglion cells (ipRGCs)4. We show that adult mice that lack ipRGCs from the early postnatal stages have impaired entrainment to time-restricted feeding, whereas ablation of ipRGCs at later stages had no effect. Innervation of ipRGCs at early postnatal stages influences IGL neurons that express neuropeptide Y (NPY) (hereafter, IGLNPY neurons), guiding the assembly of a functional IGLNPY-SCN circuit. Moreover, silencing IGLNPY neurons in adult mice mimicked the deficits that were induced by ablation of ipRGCs in the early postnatal stages, and acute inhibition of IGLNPY terminals in the SCN decreased food-anticipatory activity. Thus, innervation of ipRGCs in the early postnatal period tunes the IGLNPY-SCN circuit to allow entrainment to time-restricted feeding.


Assuntos
Ritmo Circadiano/fisiologia , Comportamento Alimentar/fisiologia , Luz , Vias Neurais , Retina/fisiologia , Animais , Axônios/fisiologia , Axônios/efeitos da radiação , Ritmo Circadiano/efeitos da radiação , Sinais (Psicologia) , Ingestão de Alimentos/fisiologia , Ingestão de Alimentos/efeitos da radiação , Comportamento Alimentar/efeitos da radiação , Feminino , Corpos Geniculados/citologia , Corpos Geniculados/fisiologia , Corpos Geniculados/efeitos da radiação , Masculino , Camundongos , Vias Neurais/efeitos da radiação , Neuropeptídeo Y/metabolismo , Retina/citologia , Retina/efeitos da radiação , Células Ganglionares da Retina/fisiologia , Células Ganglionares da Retina/efeitos da radiação , Transdução de Sinais/efeitos da radiação , Núcleo Supraquiasmático/citologia , Núcleo Supraquiasmático/fisiologia , Núcleo Supraquiasmático/efeitos da radiação , Fatores de Tempo
9.
PLoS One ; 15(4): e0231870, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32320439

RESUMO

OBJECTIVE: Interference with the transmission of sensory signals along visual and auditory pathways has been implicated in the pathogenesis of hallucinations. The relay centres for vision (the lateral geniculate nucleus) and hearing (the medial geniculate nucleus) appear to be susceptible to the uptake of circulating mercury. We therefore investigated the distribution of mercury in cells of both these geniculate nuclei. MATERIALS AND METHODS: Paraffin-embedded tissue sections containing the lateral geniculate nucleus were obtained from 50 adults (age range 20-104 years) who at autopsy had a variety of clinicopathological conditions, including neurological and psychiatric disorders. The medial geniculate nucleus was present in seven sections. Sections were stained for mercury using autometallography. Laser ablation-inductively coupled plasma-mass spectrometry was used to confirm the presence of mercury. RESULTS: Ten people had mercury in cells of the lateral geniculate nucleus, and in the medial geniculate nucleus of three of these. Medical diagnoses in these individuals were: none (3), Parkinson disease (3), and one each of depression, bipolar disorder, multiple sclerosis, and mercury self-injection. Mercury was distributed in different groups of geniculate capillary endothelial cells, neurons, oligodendrocytes, and astrocytes. Mass spectrometry confirmed the presence of mercury. CONCLUSION: Mercury is present in different combinations of cell types in the lateral and medial geniculate nuclei in a proportion of people from varied backgrounds. This raises the possibility that mercury-induced impairment of the function of the geniculate nuclei could play a part in the genesis of visual and auditory hallucinations. Although these findings do not provide a direct link between mercury in geniculate cells and hallucinations, they suggest that further investigations into the possibility of toxicant-induced hallucinations are warranted.


Assuntos
Corpos Geniculados/citologia , Mercúrio/metabolismo , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Adulto Jovem
10.
Proc Natl Acad Sci U S A ; 117(6): 3214-3219, 2020 02 11.
Artigo em Inglês | MEDLINE | ID: mdl-31974314

RESUMO

Which neural circuits undergo synaptic changes when an animal learns? Although it is widely accepted that changes in synaptic strength underlie many forms of learning and memory, it remains challenging to connect changes in synaptic strength at specific neural pathways to specific behaviors and memories. Here we introduce SYNPLA (synaptic proximity ligation assay), a synapse-specific, high-throughput, and potentially brain-wide method capable of detecting circuit-specific learning-induced synaptic plasticity.


Assuntos
Ensaios de Triagem em Larga Escala/métodos , Aprendizagem/fisiologia , Plasticidade Neuronal/fisiologia , Mapeamento de Interação de Proteínas/métodos , Sinapses , Animais , Córtex Auditivo/química , Córtex Auditivo/citologia , Córtex Auditivo/metabolismo , Células Cultivadas , Condicionamento Psicológico/fisiologia , Corpos Geniculados/química , Corpos Geniculados/citologia , Corpos Geniculados/metabolismo , Hipocampo/química , Hipocampo/citologia , Hipocampo/metabolismo , Camundongos , Proteínas do Tecido Nervoso/análise , Proteínas do Tecido Nervoso/química , Proteínas do Tecido Nervoso/metabolismo , Ratos , Sinapses/química , Sinapses/metabolismo
11.
PLoS Biol ; 18(1): e3000570, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31971946

RESUMO

Stimuli that modulate neuronal activity are not always detectable, indicating a loss of information between the modulated neurons and perception. To identify where in the macaque visual system information about periodic light modulations is lost, signal-to-noise ratios were compared across simulated cone photoreceptors, lateral geniculate nucleus (LGN) neurons, and perceptual judgements. Stimuli were drifting, threshold-contrast Gabor patterns on a photopic background. The sensitivity of LGN neurons, extrapolated to populations, was similar to the monkeys' at low temporal frequencies. At high temporal frequencies, LGN sensitivity exceeded the monkeys' and approached the upper bound set by cone photocurrents. These results confirm a loss of high-frequency information downstream of the LGN. However, this loss accounted for only about 5% of the total. Phototransduction accounted for essentially all of the rest. Together, these results show that low temporal frequency information is lost primarily between the cones and the LGN, whereas high-frequency information is lost primarily within the cones, with a small additional loss downstream of the LGN.


Assuntos
Macaca mulatta/fisiologia , Córtex Visual/citologia , Córtex Visual/fisiologia , Vias Visuais/fisiologia , Percepção Visual/fisiologia , Animais , Núcleo de Edinger-Westphal/citologia , Núcleo de Edinger-Westphal/fisiologia , Núcleo de Edinger-Westphal/efeitos da radiação , Fenômenos Eletrofisiológicos , Corpos Geniculados/citologia , Corpos Geniculados/fisiologia , Luz , Iluminação , Masculino , Neurônios/fisiologia , Neurônios/efeitos da radiação , Estimulação Luminosa , Células Fotorreceptoras Retinianas Cones/citologia , Células Fotorreceptoras Retinianas Cones/fisiologia , Células Fotorreceptoras Retinianas Cones/efeitos da radiação , Movimentos Sacádicos/fisiologia , Fatores de Tempo , Córtex Visual/efeitos da radiação , Vias Visuais/efeitos da radiação , Percepção Visual/efeitos da radiação
12.
Sci Rep ; 9(1): 16729, 2019 11 13.
Artigo em Inglês | MEDLINE | ID: mdl-31723155

RESUMO

Orexins (OXA, OXB) are hypothalamic peptides playing crucial roles in arousal, feeding, social and reward-related behaviours. A recent study on juvenile rats suggested their involvement in vision modulation due to their direct action on dorsal lateral geniculate (dLGN) neurons. The present study aimed to verify whether a similar action of OXA can be observed in adulthood. Thus, in vivo and in vitro electrophysiological recordings on adult Wistar rats across light-dark and cortical cycles were conducted under urethane anaesthesia. OXA influenced ~28% of dLGN neurons recorded in vivo by either excitation or suppression of neuronal firing. OXA-responsive neurons did not show any spatial distribution nor represent a coherent group of dLGN cells, and responded to OXA similarly across the light-dark cycle. Interestingly, some OXA-responsive neurons worked in a cortical state-dependent manner, especially during the dark phase, and 'preferred' cortical activation over slow-wave activity induced by urethane. The corresponding patch clamp study confirmed these results by showing that < 20% of dLGN neurons were excited by OXA under both light regimes. The results suggest that OXA is involved in the development of the visual system rather than in visual processes and further implicate OXA in the mediation of circadian and arousal-related activity.


Assuntos
Potenciais de Ação , Ritmo Circadiano , Corpos Geniculados/fisiologia , Neurônios/fisiologia , Orexinas/farmacologia , Transmissão Sináptica , Animais , Fenômenos Eletrofisiológicos , Corpos Geniculados/citologia , Masculino , Neurônios/citologia , Receptores de Orexina/metabolismo , Ratos , Ratos Wistar
13.
Cell Rep ; 27(13): 3733-3740.e3, 2019 06 25.
Artigo em Inglês | MEDLINE | ID: mdl-31242407

RESUMO

The retinas of rabbits and rodents have directionally selective (DS) retinal ganglion cells that convey directional signals through the lateral geniculate nucleus (LGN) of the thalamus to the primary visual cortex (V1). Notably, the function and synaptic impact in V1 of these directional LGN signals are unknown. Here we measured, in awake rabbits, the synaptic impact generated in V1 by individual LGN DS neurons. We show that these neurons make fast and strong connections in layers 4 and 6, with postsynaptic effects that are similar to those made by LGN concentric neurons, the main thalamic drivers of V1. By contrast, the synaptic impact of LGN DS neurons on superficial cortical layers was not detectable. These results suggest that LGN DS neurons activate a cortical column by targeting the main cortical input layers and that the role of DS input to superficial cortical layers is likely to be weak and/or modulatory.


Assuntos
Corpos Geniculados/metabolismo , Neurônios/metabolismo , Transmissão Sináptica , Córtex Visual/metabolismo , Vias Visuais/metabolismo , Animais , Corpos Geniculados/citologia , Neurônios/citologia , Coelhos , Córtex Visual/citologia , Vias Visuais/citologia
14.
Biol Cybern ; 113(4): 453-464, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31243531

RESUMO

To understand how anatomy and physiology allow an organism to perform its function, it is important to know how information that is transmitted by spikes in the brain is received and encoded. A natural question is whether the spike rate alone encodes the information about a stimulus (rate code), or additional information is contained in the temporal pattern of the spikes (temporal code). Here we address this question using data from the cat Lateral Geniculate Nucleus (LGN), which is the visual portion of the thalamus, through which visual information from the retina is communicated to the visual cortex. We analyzed the responses of LGN neurons to spatially homogeneous spots of various sizes with temporally random luminance modulation. We compared the Firing Rate with the Shannon Information Transmission Rate , which quantifies the information contained in the temporal relationships between spikes. We found that the behavior of these two rates can differ quantitatively. This suggests that the energy used for spiking does not translate directly into the information to be transmitted. We also compared Firing Rates with Information Rates for X-ON and X-OFF cells. We found that, for X-ON cells the Firing Rate and Information Rate often behave in a completely different way, while for X-OFF cells these rates are much more highly correlated. Our results suggest that for X-ON cells a more efficient "temporal code" is employed, while for X-OFF cells a straightforward "rate code" is used, which is more reliable and is correlated with energy consumption.


Assuntos
Potenciais de Ação/fisiologia , Corpos Geniculados/citologia , Corpos Geniculados/fisiologia , Processos Mentais/fisiologia , Neurônios/fisiologia , Animais , Gatos , Estimulação Luminosa/métodos , Córtex Visual/citologia , Córtex Visual/fisiologia , Vias Visuais/citologia , Vias Visuais/fisiologia
15.
J Neurophysiol ; 121(5): 1938-1952, 2019 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-30917065

RESUMO

Repetitive visual stimulation profoundly changes sensory processing in the primary visual cortex (V1). We show how the associated adaptive changes are linked to an altered flow of synaptic activation across the V1 laminar microcircuit. Using repeated visual stimulation, we recorded layer-specific responses in V1 of two fixating monkeys. We found that repetition-related spiking suppression was most pronounced outside granular V1 layers that receive the main retinogeniculate input. This repetition-related response suppression was robust to alternating stimuli between the eyes, in line with the notion that repetition-related adaptation is predominantly of cortical origin. Most importantly, current source density (CSD) analysis, which provides an estimate of local net depolarization, revealed that synaptic processing during repeated stimulation was most profoundly affected within supragranular layers, which harbor the bulk of cortico-cortical connections. Direct comparison of the temporal evolution of laminar CSD and spiking activity showed that stimulus repetition first affected supragranular synaptic currents, which translated into a reduction of stimulus-evoked spiking across layers. Together, these results suggest that repetition induces an altered state of intracortical processing that underpins visual adaptation. NEW & NOTEWORTHY Our survival depends on our brains rapidly adapting to ever changing environments. A well-studied form of adaptation occurs whenever we encounter the same or similar stimuli repeatedly. We show that this repetition-related adaptation is supported by systematic changes in the flow of sensory activation across the laminar cortical microcircuitry of primary visual cortex. These results demonstrate how adaptation impacts neuronal interactions across cortical circuits.


Assuntos
Adaptação Fisiológica , Potenciais Evocados Visuais , Córtex Visual/fisiologia , Animais , Feminino , Corpos Geniculados/citologia , Corpos Geniculados/fisiologia , Macaca radiata , Masculino , Neurônios/fisiologia , Córtex Visual/citologia
16.
J Neurosci ; 39(20): 3856-3866, 2019 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-30842249

RESUMO

The dorsal lateral geniculate nucleus (dLGN) of the mouse is a model system to study the development of thalamic circuitry. Most studies focus on relay neurons of dLGN, yet little is known about the development of the other principal cell type, intrinsic interneurons. Here we examined whether the structure and function of interneurons relies on retinal signaling. We took a loss-of-function approach and crossed GAD67-GFP mice, which express GFP in dLGN interneurons, with math5 nulls (math5-/-), mutants that lack retinal ganglion cells and retinofugal projections. In vitro recordings and 3-D reconstructions of biocytin-filled interneurons at different postnatal ages showed their development is a multistaged process involving migration, arbor remodeling, and synapse formation. Arbor remodeling begins during the second postnatal week, after migration to and dispersion within dLGN is complete. This phase includes a period of exuberant branching where arbors grow in number, complexity, and field size. Such growth is followed by branch pruning and stabilization, as interneurons adopt a bipolar architecture. The absence of retinal signaling disrupts this process. The math5-/- interneurons fail to branch and prune, and instead maintain a simple, sparse architecture. To test how such defects influence connectivity with dLGN relay neurons, we used DHPG [(RS)-3,5-dihydroxyphenylglycine], the mGluR1,5 agonist that targets F2 terminals. This led to substantial increases in IPSC activity among WT relay neurons but had little impact in math5-/- mice. Together, these data suggest that retinal signaling is needed to support the arbor elaboration and synaptic connectivity of dLGN interneurons.SIGNIFICANCE STATEMENT Presently, our understanding about the development of the dorsal lateral geniculate nucleus is limited to circuits involving excitatory thalamocortical relay neurons. Here we show that the other principal cell type, intrinsic interneurons, has a multistaged developmental plan that relies on retinal innervation. These findings indicate that signaling from the periphery guides the maturation of interneurons and the establishment of inhibitory thalamic circuits.


Assuntos
Potenciais de Ação , Corpos Geniculados/crescimento & desenvolvimento , Interneurônios/fisiologia , Células Ganglionares da Retina/fisiologia , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Fatores de Transcrição Hélice-Alça-Hélice Básicos/fisiologia , Movimento Celular , Feminino , Neurônios GABAérgicos/citologia , Neurônios GABAérgicos/fisiologia , Corpos Geniculados/citologia , Interneurônios/citologia , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/fisiologia , Vias Visuais/crescimento & desenvolvimento
17.
Eur J Neurosci ; 50(4): 2683-2693, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-30803080

RESUMO

Orexins/hypocretins are hypothalamic neuropeptides that have a variety of functions, including maintenance of arousal, control over the sleep/wake cycle, reward and feeding. Accumulating evidence links orexins to the time-keeping system with a documented action in the master clock-the suprachiasmatic nucleus. The intergeniculate leaflet (IGL) is a thalamic structure with the well-known function of collecting photic and non-photic cues to adjust the rhythm of the suprachiasmatic nucleus to changing environmental conditions. The IGL consists of GABAergic neurons that are intrinsically active, even in slice preparations. Our previous studies revealed the excitatory postsynaptic effects of orexins on single IGL neurons, even though the ionic mechanism underlying this effect remained elusive. Therefore, in this study, we used patch clamp electrophysiology to identify the ions and distinct ion channels responsible for the observed depolarisations. The major finding of this article is that the orexin A-evoked depolarisation of IGL neurons depends on non-selective cation channels, implicating the orexinergic tone in establishing the basal firing rate in these cells. The data presented here strengthen the mutual connections between the time-keeping and orexinergic systems.


Assuntos
Corpos Geniculados/efeitos dos fármacos , Canais Iônicos/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Orexinas/farmacologia , Núcleos Talâmicos/efeitos dos fármacos , Animais , Fenômenos Eletrofisiológicos/efeitos dos fármacos , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Corpos Geniculados/citologia , Masculino , Técnicas de Patch-Clamp , Potássio/fisiologia , Ratos , Ratos Wistar , Sódio/fisiologia , Núcleo Supraquiasmático/efeitos dos fármacos , Núcleos Talâmicos/citologia , Ácido gama-Aminobutírico/fisiologia
18.
Neuron ; 102(2): 462-476.e8, 2019 04 17.
Artigo em Inglês | MEDLINE | ID: mdl-30799020

RESUMO

Mouse vision is based on the parallel output of more than 30 functional types of retinal ganglion cells (RGCs). Little is known about how representations of visual information change between retina and dorsolateral geniculate nucleus (dLGN) of the thalamus, the main relay between retina and cortex. Here, we functionally characterized responses of retrogradely labeled dLGN-projecting RGCs and dLGN neurons to the same set of visual stimuli. We found that many of the previously identified functional RGC types innervate dLGN, which maintained a high degree of functional diversity. Using a linear model to assess functional connectivity between RGC types and dLGN neurons, we found that responses of dLGN neurons could be predicted as linear combination of inputs from on average five RGC types, but only two of those had the strongest functional impact. Thus, mouse dLGN receives functional input from a diverse population of RGC types with limited convergence.


Assuntos
Corpos Geniculados/fisiologia , Células Ganglionares da Retina/fisiologia , Visão Ocular/fisiologia , Vias Visuais/fisiologia , Animais , Eletroencefalografia , Corpos Geniculados/citologia , Modelos Lineares , Camundongos , Neurônios/citologia , Neurônios/fisiologia , Estimulação Luminosa
19.
J Comp Neurol ; 527(6): 1118-1126, 2019 04 15.
Artigo em Inglês | MEDLINE | ID: mdl-30536721

RESUMO

The medial geniculate body (MG) receives a large input from the ipsilateral inferior colliculus (IC) and a smaller but substantial input from the contralateral IC. Both crossed and uncrossed inputs comprise a large percentage of glutamatergic cells and a smaller percentage of GABAergic cells. We used double labeling with fluorescent retrograde tracers to identify individual IC cells that project bilaterally to the MGs in adult guinea pigs. We also used immunohistochemistry for glutamic acid decarboxylase to distinguish GABAergic from glutamatergic cells that project bilaterally to the MG. We found cells in the IC that contained both retrograde tracers, indicating that they project bilaterally. Across cases, the bilaterally projecting cells constituted up to 37% of the cells that project to the ipsilateral MG and up to 73% of the cells that project to the contralateral MG. GABAergic cells averaged 20% of the bilaterally-projecting population. We conclude that a population of IC cells sends branching axonal projections to innervate the MG bilaterally. Most of the neurons in this population are glutamatergic, with a minority that are GABAergic. A mixed projection, with glutamatergic cells outnumbering GABAergic cells, originates from each of the major IC subdivisions (central nucleus, dorsal cortex, and lateral cortex). The bilaterally projecting cells are likely to serve functions different from the larger unilateral projections, perhaps synchronizing activity on the two sides of the auditory brain.


Assuntos
Vias Auditivas/citologia , Corpos Geniculados/citologia , Colículos Inferiores/citologia , Neurônios/citologia , Animais , Feminino , Cobaias , Masculino
20.
J Comp Neurol ; 527(3): 522-534, 2019 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-29473163

RESUMO

The dorsal lateral geniculate nucleus of the thalamus (LGN) receives the main outputs of both eyes and relays those signals to the visual cortex. Each retina projects to separate layers of the LGN so that each LGN neuron is innervated by a single eye. In line with this anatomical separation, visual responses of almost all of LGN neurons are driven by one eye only. Nonetheless, many LGN neurons are sensitive to what is shown to the other eye as their visual responses differ when both eyes are stimulated compared to when the driving eye is stimulated in isolation. This, predominantly suppressive, binocular modulation of LGN responses might suggest that the LGN is the first location in the primary visual pathway where the outputs from the two eyes interact. Indeed, the LGN features several anatomical structures that would allow for LGN neurons responding to one eye to modulate neurons that respond to the other eye. However, it is also possible that binocular response modulation in the LGN arises indirectly as the LGN also receives input from binocular visual structures. Here we review the extant literature on the effects of binocular stimulation on LGN spiking responses, highlighting findings from cats and primates, and evaluate the neural circuits that might mediate binocular response modulation in the LGN.


Assuntos
Corpos Geniculados/fisiologia , Visão Binocular/fisiologia , Córtex Visual/fisiologia , Vias Visuais/fisiologia , Potenciais de Ação/fisiologia , Animais , Corpos Geniculados/citologia , Humanos , Estimulação Luminosa/métodos , Retina/fisiologia , Córtex Visual/citologia , Campos Visuais/fisiologia , Vias Visuais/citologia
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...