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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.
Invest Ophthalmol Vis Sci ; 62(6): 17, 2021 05 03.
Artigo em Inglês | MEDLINE | ID: mdl-33988692

RESUMO

Purpose: The purpose of this study was to characterize summation of temporal L- and M-cone contrasts in the parvo- (P-) and magnocellular (M-) pathways in glaucoma and the relationship between the respective temporal contrast sensitivities (tCS) and clinical parameters. Methods: Perifoveal tCS to isolated or combined L- and M-cone contrasts (with different contrast ratios, and therefore different luminance and chromatic components) were measured at different temporal frequencies (at 1 or 2 Hz and at 20 Hz) using triple silent substitution in 73 subjects (13 healthy, 25 with glaucoma, and 35 with perimetric glaucoma). A vector summation model was used to analyze whether perception was driven by the P-pathway, the M-pathway, or both. Using this model, L- and M-cone input strengths (AL, AM) and phase differences between L- and M-cone inputs were estimated. Results: Perception was always mediated by the P-pathway at low frequencies, as indicated by a median phase angle of 179.84 degrees (cone opponency) and a median AL/AM ratio of 1.04 (balanced L- and M-cone input strengths). In contrast, perception was exclusively mediated by the M-pathway at higher frequencies (input strength not balanced: AL/AM = 2.94, median phase angles = 130.17 degrees). Differences in phase were not significant between diagnosis groups (Kruskal-Wallis = 0.092 for P- and 0.35 for M-pathway). We found differences between groups only for the M-pathway (L-cone tCS deviations at 20 Hz were significantly lower in the patients with glaucoma P = 0.014, with a strong tendency in M-cones P = 0.049). L-cone driven tCS deviations at 20 Hz were linearly correlated with perimetric mean defect (MD) and quadratically correlated with retinal nerve fiber layer (RNFL) thickness. Conclusions: Unaltered phase angles between L- and M-cone inputs in glaucoma indicated intact temporal processing. Only in the M-pathway, contrast sensitivity deviations were closely related to diagnosis group, MD, and RNFL thickness, indicating M-pathway involvement.


Assuntos
Opsinas dos Cones/fisiologia , Sensibilidades de Contraste/fisiologia , Corpos Geniculados/fisiologia , Glaucoma de Ângulo Aberto/fisiopatologia , Células Fotorreceptoras Retinianas Cones/fisiologia , Células Ganglionares da Retina/fisiologia , Adulto , Idoso , Feminino , Humanos , Pressão Intraocular/fisiologia , Masculino , Pessoa de Meia-Idade , Tomografia de Coerência Óptica , Testes de Campo Visual , Campos Visuais/fisiologia , Vias Visuais/fisiologia
4.
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
5.
Neuroimage ; 233: 117924, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33753240

RESUMO

Functional magnetic resonance imaging (fMRI) based on the blood oxygenation level-dependent (BOLD) contrast has become an indispensable tool in neuroscience. However, the BOLD signal is nonlocal, lacking quantitative measurement of oxygenation fluctuation. This preclinical study aimed to introduced functional quantitative susceptibility mapping (fQSM) to complement BOLD-fMRI to quantitatively assess the local susceptibility and venous oxygen saturation (SvO2). Rats were subjected to a 5 Hz flashing light and the different inhaled oxygenation levels (30% and 100%) were used to observe the venous susceptibility to quantify SvO2. Phase information was extracted to produce QSM, and the activation responses of magnitude (conventional BOLD) and the QSM time-series were analyzed. During light stimulation, the susceptibility change of fQSM was four times larger than the BOLD signal change in both inhalation oxygenation conditions. Moreover, the responses in the fQSM map were more restricted to the visual pathway, such as the lateral geniculate nucleus and superior colliculus, compared with the relatively diffuse distributions in the BOLD map. Also, the calibrated SvO2 was approximately 84% (88%) when the task was on, 83% (87%) when the task was off during 30% (and during 100%) oxygen inhalation. This is the first fQSM study in a small animal model and increases our understanding of fQSM in the brains of small animals. This study demonstrated the feasibility, sensitivity, and specificity of fQSM using light stimulus, as fQSM provides quantitative clues as well as localized information, complementing the defects of BOLD-fMRI. In addition to neural activity, fQSM also assesses SvO2 as supplementary information while BOLD-fMRI dose not. Accordingly, the fQSM technique could be a useful quantitative tool for functional studies, such as longitudinal follow up of neurodegenerative diseases, functional recovery after brain surgery, and negative BOLD studies.


Assuntos
Mapeamento Encefálico/métodos , Corpos Geniculados/diagnóstico por imagem , Imageamento por Ressonância Magnética/métodos , Estimulação Luminosa/métodos , Colículos Superiores/diagnóstico por imagem , Vias Visuais/diagnóstico por imagem , Animais , Encéfalo/diagnóstico por imagem , Encéfalo/fisiologia , Corpos Geniculados/fisiologia , Masculino , Ratos , Ratos Sprague-Dawley , Colículos Superiores/fisiologia , Vias Visuais/fisiologia
6.
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
7.
J Neurosci ; 41(11): 2382-2392, 2021 03 17.
Artigo em Inglês | MEDLINE | ID: mdl-33500275

RESUMO

The initial encoding of visual information primarily from the contralateral visual field is a fundamental organizing principle of the primate visual system. Recently, the presence of such retinotopic sensitivity has been shown to extend well beyond early visual cortex to regions not historically considered retinotopically sensitive. In particular, human scene-selective regions in parahippocampal and medial parietal cortex exhibit prominent biases for the contralateral visual field. Here, we used fMRI to test the hypothesis that the human hippocampus, which is thought to be anatomically connected with these scene-selective regions, would also exhibit a biased representation of contralateral visual space. First, population receptive field (pRF) mapping with scene stimuli revealed strong biases for the contralateral visual field in bilateral hippocampus. Second, the distribution of retinotopic sensitivity suggested a more prominent representation in anterior medial portions of the hippocampus. Finally, the contralateral bias was confirmed in independent data taken from the Human Connectome Project (HCP) initiative. The presence of contralateral biases in the hippocampus, a structure considered by many as the apex of the visual hierarchy, highlights the truly pervasive influence of retinotopy. Moreover, this finding has important implications for understanding how visual information relates to the allocentric global spatial representations known to be encoded therein.SIGNIFICANCE STATEMENT Retinotopic encoding of visual information is an organizing principle of visual cortex. Recent work demonstrates this sensitivity in structures far beyond early visual cortex, including those anatomically connected to the hippocampus. Here, using population receptive field (pRF) modeling in two independent sets of data we demonstrate a consistent bias for the contralateral visual field in bilateral hippocampus. Such a bias highlights the truly pervasive influence of retinotopy, with important implications for understanding how the presence of retinotopy relates to more allocentric spatial representations.


Assuntos
Hipocampo/fisiologia , Percepção Espacial/fisiologia , Percepção Visual/fisiologia , Adulto , Mapeamento Encefálico/métodos , Conectoma , Feminino , Lateralidade Funcional , Corpos Geniculados/fisiologia , Hipocampo/diagnóstico por imagem , Humanos , Imageamento por Ressonância Magnética , Masculino , Giro Para-Hipocampal/fisiologia , Estimulação Luminosa , Retina/fisiologia , Campos Visuais , Adulto Jovem
8.
J Neurosci ; 41(8): 1755-1768, 2021 02 24.
Artigo em Inglês | MEDLINE | ID: mdl-33443074

RESUMO

After damage to the primary visual cortex (V1), conscious vision is impaired. However, some patients can respond to visual stimuli presented in their lesion-affected visual field using residual visual pathways bypassing V1. This phenomenon is called "blindsight." Many studies have tried to identify the brain regions responsible for blindsight, and the pulvinar and/or lateral geniculate nucleus (LGN) are suggested to play key roles as the thalamic relay of visual signals. However, there are critical problems regarding these preceding studies in that subjects with different sized lesions and periods of time after lesioning were investigated; furthermore, the ability of blindsight was assessed with different measures. In this study, we used double dissociation to clarify the roles of the pulvinar and LGN by pharmacological inactivation of each region and investigated the effects in a simple task with visually guided saccades (VGSs) using monkeys with a unilateral V1 lesion, by which nearly all of the contralesional visual field was affected. Inactivating either the ipsilesional pulvinar or LGN impaired VGS toward a visual stimulus in the affected field. In contrast, inactivation of the contralesional pulvinar had no clear effect, but inactivation of the contralesional LGN impaired VGS to the intact visual field. These results suggest that the pulvinar and LGN play key roles in performing the simple VGS task after V1 lesioning, and that the visuomotor functions of blindsight monkeys were supported by plastic changes in the visual pathway involving the pulvinar, which emerged after V1 lesioning.SIGNIFICANCE STATEMENT Many studies have been devoted to understanding the mechanism of mysterious symptom called "blindsight," in which patients with damage to the primary visual cortex (V1) can respond to visual stimuli despite loss of visual awareness. However, there is still a debate on the thalamic relay of visual signals. In this study, to pin down the issue, we tried double dissociation in the same subjects (hemi-blindsight macaque monkeys) and clarified that the lateral geniculate nucleus (LGN) plays a major role in simple visually guided saccades in the intact state, while both pulvinar and LGN critically contribute after the V1 lesioning, suggesting that plasticity in the visual pathway involving the pulvinar underlies the blindsight.


Assuntos
Corpos Geniculados/fisiologia , Pulvinar/fisiologia , Movimentos Sacádicos/fisiologia , Córtex Visual/lesões , Percepção Visual/fisiologia , Animais , Feminino , Lateralidade Funcional/fisiologia , Macaca fuscata , Estimulação Luminosa , Vias Visuais/fisiologia
9.
Nature ; 589(7840): 96-102, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-33208951

RESUMO

The hippocampus has a major role in encoding and consolidating long-term memories, and undergoes plastic changes during sleep1. These changes require precise homeostatic control by subcortical neuromodulatory structures2. The underlying mechanisms of this phenomenon, however, remain unknown. Here, using multi-structure recordings in macaque monkeys, we show that the brainstem transiently modulates hippocampal network events through phasic pontine waves known as pontogeniculooccipital waves (PGO waves). Two physiologically distinct types of PGO wave appear to occur sequentially, selectively influencing high-frequency ripples and low-frequency theta events, respectively. The two types of PGO wave are associated with opposite hippocampal spike-field coupling, prompting periods of high neural synchrony of neural populations during periods of ripple and theta instances. The coupling between PGO waves and ripples, classically associated with distinct sleep stages, supports the notion that a global coordination mechanism of hippocampal sleep dynamics by cholinergic pontine transients may promote systems and synaptic memory consolidation as well as synaptic homeostasis.


Assuntos
Corpos Geniculados/fisiologia , Hipocampo/fisiologia , Lobo Occipital/fisiologia , Ponte/fisiologia , Sono/fisiologia , Ritmo Teta/fisiologia , Animais , Pareamento Cromossômico/fisiologia , Feminino , Homeostase , Macaca/fisiologia , Consolidação da Memória/fisiologia , Plasticidade Neuronal , Fases do Sono/fisiologia
10.
Elife ; 92020 07 08.
Artigo em Inglês | MEDLINE | ID: mdl-32639231

RESUMO

Learning to associate sensory stimuli with a chosen action involves a dynamic interplay between cortical and thalamic circuits. While the cortex has been widely studied in this respect, how the thalamus encodes learning-related information is still largely unknown. We studied learning-related activity in the medial geniculate body (MGB; Auditory thalamus), targeting mainly the dorsal and medial regions. Using fiber photometry, we continuously imaged population calcium dynamics as mice learned a go/no-go auditory discrimination task. The MGB was tuned to frequency and responded to cognitive features like the choice of the mouse within several hundred milliseconds. Encoding of choice in the MGB increased with learning, and was highly correlated with the learning curves of the mice. MGB also encoded motor parameters of the mouse during the task. These results provide evidence that the MGB encodes task- motor- and learning-related information.


Assuntos
Percepção Auditiva/fisiologia , Corpos Geniculados/fisiologia , Aprendizagem/fisiologia , Animais , Feminino , Camundongos , Camundongos Endogâmicos C57BL
11.
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
12.
PLoS Biol ; 18(5): e3000674, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32396574

RESUMO

Animals use auditory cues generated by defensive responses of others to detect impending danger. Here we identify a neural circuit in rats involved in the detection of one such auditory cue, the cessation of movement-evoked sound resulting from freezing. This circuit comprises the dorsal subnucleus of the medial geniculate body (MGD) and downstream areas, the ventral area of the auditory cortex (VA), and the lateral amygdala (LA). This study suggests a role for the auditory offset pathway in processing a natural sound cue of threat.


Assuntos
Córtex Auditivo/fisiologia , Percepção Auditiva/fisiologia , Complexo Nuclear Basolateral da Amígdala/fisiologia , Corpos Geniculados/fisiologia , Animais , Aprendizagem da Esquiva/fisiologia , Sinais (Psicologia) , Masculino , Ratos Sprague-Dawley
13.
J Neurosci ; 40(26): 5019-5032, 2020 06 24.
Artigo em Inglês | MEDLINE | ID: mdl-32350041

RESUMO

Even though the lateral geniculate nucleus of the thalamus (LGN) is associated with form vision, that is not its sole role. Only the dorsal portion of LGN (dLGN) projects to V1. The ventral division (vLGN) connects subcortically, sending inhibitory projections to sensorimotor structures, including the superior colliculus (SC) and regions associated with certain behavioral states, such as fear (Monavarfeshani et al., 2017; Salay et al., 2018). We combined computational, physiological, and anatomical approaches to explore visual processing in vLGN of mice of both sexes, making comparisons to dLGN and SC for perspective. Compatible with past, qualitative descriptions, the receptive fields we quantified in vLGN were larger than those in dLGN, and most cells preferred bright versus dark stimuli (Harrington, 1997). Dendritic arbors spanned the length and/or width of vLGN and were often asymmetric, positioned to collect input from large but discrete territories. By contrast, arbors in dLGN are compact (Krahe et al., 2011). Consistent with spatially coarse receptive fields in vLGN, visually evoked changes in spike timing were less precise than for dLGN and SC. Notably, however, the membrane currents and spikes of some cells in vLGN displayed gamma oscillations whose phase and strength varied with stimulus pattern, as for SC (Stitt et al., 2013). Thus, vLGN can engage its targets using oscillation-based and conventional rate codes. Finally, dark shadows activate SC and drive escape responses, whereas vLGN prefers bright stimuli. Thus, one function of long-range inhibitory projections from vLGN might be to enable movement by releasing motor targets, such as SC, from suppression.SIGNIFICANCE STATEMENT Only the dorsal lateral geniculate nucleus (dLGN) connects to cortex to serve form vision; the ventral division (vLGN) projects subcortically to sensorimotor nuclei, including the superior colliculus (SC), via long-range inhibitory connections. Here, we asked how vLGN processes visual information, making comparisons with dLGN and SC for perspective. Cells in vLGN versus dLGN had wider dendritic arbors, larger receptive fields, and fired with lower temporal precision, consistent with a modulatory role. Like SC, but not dLGN, visual stimuli entrained oscillations in vLGN, perhaps reflecting shared strategies for visuomotor processing. Finally, most neurons in vLGN preferred bright shapes, whereas dark stimuli activate SC and drive escape behaviors, suggesting that vLGN enables rapid movement by releasing target motor structures from inhibition.


Assuntos
Corpos Geniculados/fisiologia , Percepção Visual/fisiologia , Animais , Potenciais Evocados Visuais/fisiologia , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Vias Visuais/fisiologia
14.
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
15.
Proc Natl Acad Sci U S A ; 117(23): 13066-13077, 2020 06 09.
Artigo em Inglês | MEDLINE | ID: mdl-32461374

RESUMO

Layer 6 (L6) is the sole purveyor of corticothalamic (CT) feedback to first-order thalamus and also sends projections to higher-order thalamus, yet how it engages the full corticothalamic circuit to contribute to sensory processing in an awake animal remains unknown. We sought to elucidate the functional impact of L6CT projections from the primary visual cortex to the dorsolateral geniculate nucleus (first-order) and pulvinar (higher-order) using optogenetics and extracellular electrophysiology in awake mice. While sustained L6CT photostimulation suppresses activity in both visual thalamic nuclei in vivo, moderate-frequency (10 Hz) stimulation powerfully facilitates thalamic spiking. We show that each stimulation paradigm differentially influences the balance between monosynaptic excitatory and disynaptic inhibitory corticothalamic pathways to the dorsolateral geniculate nucleus and pulvinar, as well as the prevalence of burst versus tonic firing. Altogether, our results support a model in which L6CTs modulate first- and higher-order thalamus through parallel excitatory and inhibitory pathways that are highly dynamic and context-dependent.


Assuntos
Corpos Geniculados/fisiologia , Pulvinar/fisiologia , Córtex Visual/fisiologia , Animais , Estimulação Elétrica , Eletrodos Implantados , Feminino , Masculino , Camundongos , Microeletrodos , Optogenética , Técnicas Estereotáxicas , Vias Visuais
16.
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
17.
J Vis ; 20(4): 16, 2020 04 09.
Artigo em Inglês | MEDLINE | ID: mdl-32330221

RESUMO

The response to contrast is one of the most important functions of the macaque primary visual cortex, V1, but up to now there has not been an adequate theory for it. To fill this gap in our understanding of cortical function, we built and analyzed a new large-scale, biologically constrained model of the input layer, 4Cα, of macaque V1. We called the new model CSY2. We challenged CSY2 with a three-parameter family of visual stimuli that varied in contrast, orientation, and spatial frequency. CSY2 accurately simulated experimental data and made many new predictions. It accounted for 1) the shapes of firing-rate-versus-contrast functions, 2) orientation and spatial frequency tuning versus contrast, and 3) the approximate contrast-invariance of cortical activity maps. Post-analysis revealed that the mechanisms that were needed to produce the successful simulations of contrast response included strong recurrent excitation and inhibition that find dynamic equilibria across the cortical surface, dynamic feedback between L6 and L4, and synaptic dynamics like inhibitory synaptic depression.


Assuntos
Sensibilidades de Contraste/fisiologia , Corpos Geniculados/fisiologia , Modelos Neurológicos , Córtex Visual/fisiologia , Vias Visuais/fisiologia , Animais , Mapeamento Encefálico , Simulação por Computador , Macaca , Neurônios/fisiologia , Orientação/fisiologia
18.
Neuron ; 106(1): 21-36, 2020 04 08.
Artigo em Inglês | MEDLINE | ID: mdl-32272065

RESUMO

Since the discovery of ocular dominance plasticity, neuroscientists have understood that changes in visual experience during a discrete developmental time, the critical period, trigger robust changes in the visual cortex. State-of-the-art tools used to probe connectivity with cell-type-specific resolution have expanded the understanding of circuit changes underlying experience-dependent plasticity. Here, we review the visual circuitry of the mouse, describing projections from retina to thalamus, between thalamus and cortex, and within cortex. We discuss how visual circuit development leads to precise connectivity and identify synaptic loci, which can be altered by activity or experience. Plasticity extends to visual features beyond ocular dominance, involving subcortical and cortical regions, and connections between cortical inhibitory interneurons. Experience-dependent plasticity contributes to the alignment of networks spanning retina to thalamus to cortex. Disruption of this plasticity may underlie aberrant sensory processing in some neurodevelopmental disorders.


Assuntos
Dominância Ocular/fisiologia , Plasticidade Neuronal/fisiologia , Retina/fisiologia , Tálamo/fisiologia , Córtex Visual/fisiologia , Animais , Período Crítico Psicológico , Corpos Geniculados/crescimento & desenvolvimento , Corpos Geniculados/fisiologia , Núcleos Laterais do Tálamo/crescimento & desenvolvimento , Núcleos Laterais do Tálamo/fisiologia , Camundongos , Transtornos do Neurodesenvolvimento/fisiopatologia , Retina/crescimento & desenvolvimento , Colículos Superiores/crescimento & desenvolvimento , Colículos Superiores/fisiologia , Núcleo Supraquiasmático/crescimento & desenvolvimento , Núcleo Supraquiasmático/fisiologia , Sinapses/fisiologia , Tálamo/crescimento & desenvolvimento , Visão Binocular/fisiologia , Córtex Visual/crescimento & desenvolvimento , Vias Visuais/crescimento & desenvolvimento , Vias Visuais/fisiologia
19.
World Neurosurg ; 137: 310-318, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32036065

RESUMO

The thalamus is a deep cerebral structure that is crucial for proper neurological functioning as it transmits signals from nearly all pathways in the body. Insult to the thalamus can, therefore, result in complex syndromes involving sensation, cognition, executive function, fine motor control, emotion, and arousal, to name a few. Specific territories in the thalamus that are supplied by deep cerebral arteries have been shown to correlate with clinical symptoms. The aim of this review is to enhance our understanding of the arterial anatomy of the thalamus and the complications that can arise from lesions to it by considering the functions of known thalamic nuclei supplied by each vascular territory.


Assuntos
Artéria Basilar/anatomia & histologia , Infarto Encefálico/fisiopatologia , Círculo Arterial do Cérebro/anatomia & histologia , Artéria Cerebral Posterior/anatomia & histologia , Tálamo/irrigação sanguínea , Núcleos Anteriores do Tálamo/anatomia & histologia , Núcleos Anteriores do Tálamo/irrigação sanguínea , Núcleos Anteriores do Tálamo/fisiologia , Corpos Geniculados/anatomia & histologia , Corpos Geniculados/irrigação sanguínea , Corpos Geniculados/fisiologia , Humanos , Núcleos Laterais do Tálamo/anatomia & histologia , Núcleos Laterais do Tálamo/irrigação sanguínea , Núcleos Laterais do Tálamo/fisiologia , Núcleo Mediodorsal do Tálamo/anatomia & histologia , Núcleo Mediodorsal do Tálamo/irrigação sanguínea , Núcleo Mediodorsal do Tálamo/fisiologia , Pulvinar/anatomia & histologia , Pulvinar/irrigação sanguínea , Pulvinar/fisiologia , Tálamo/anatomia & histologia , Tálamo/fisiologia , Núcleos Ventrais do Tálamo/anatomia & histologia , Núcleos Ventrais do Tálamo/irrigação sanguínea , Núcleos Ventrais do Tálamo/fisiologia
20.
Neuropsychologia ; 138: 107352, 2020 02 17.
Artigo em Inglês | MEDLINE | ID: mdl-31958409

RESUMO

The ability to identify facial expressions rapidly and accurately is central to human evolution. Previous studies have demonstrated that this ability relies to a large extent on the magnocellular, rather than parvocellular, visual pathway, which is biased toward processing low spatial frequencies. Despite the generally consistent finding, no study to date has investigated the reliability of this effect over time. In the present study, 40 participants completed a facial emotion identification task (fearful, happy, or neutral faces) using facial images presented at three different spatial frequencies (low, high, or broad spatial frequency), at two time points separated by one year. Bayesian statistics revealed an advantage for the magnocellular pathway in processing facial expressions; however, no effect for time was found. Furthermore, participants' RT patterns of results were highly stable over time. Our replication, together with the consistency of our measurements within subjects, underscores the robustness of this effect. This capacity, therefore, may be considered in a trait-like manner, suggesting that individuals may possess various ability levels for processing facial expressions that can be captured in behavioral measurements.


Assuntos
Emoções/fisiologia , Expressão Facial , Reconhecimento Facial/fisiologia , Corpos Geniculados/fisiologia , Vias Visuais/fisiologia , Adulto , Variação Biológica Individual , Feminino , Seguimentos , Humanos , Individualidade , Masculino , Adulto Jovem
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