RESUMO
Most studies on the development of the visual system have focused on the mechanisms shaping early visual stages up to the level of primary visual cortex (V1). Much less is known about the development of the stages after V1 that handle the higher visual functions fundamental to everyday life. The standard model for the maturation of these areas is that it occurs sequentially, according to the positions of areas in the adult hierarchy. Yet, the existing literature reviewed here paints a different picture, one in which the adult configuration emerges through a sequence of unique network configurations that are not mere partial versions of the adult hierarchy. In addition to studying higher visual development per se to fill major gaps in knowledge, it will be crucial to adopt a network-level perspective in future investigations to unravel normal developmental mechanisms, identify vulnerabilities to developmental disorders, and eventually devise treatments for these disorders.
Assuntos
Córtex Visual , Vias Visuais , Humanos , Vias Visuais/fisiologia , Animais , Córtex Visual/fisiologia , Córtex Visual/crescimento & desenvolvimento , Rede Nervosa/fisiologia , Visão Ocular/fisiologia , Percepção Visual/fisiologia , Córtex Visual Primário/fisiologiaRESUMO
In the primary visual cortex area V1 activation of inhibitory interneurons, which provide negative feedback for excitatory pyramidal neurons, can improve visual response reliability and orientation selectivity. Moreover, optogenetic activation of one class of interneurons, parvalbumin (PV) positive cells, reduces the receptive field (RF) width. These data suggest that in V1 the negative feedback improves visual information processing. However, according to information theory, noise can limit information content in a signal, and to the best of our knowledge, in V1 signal-to-noise ratio (SNR) has never been estimated following either pyramidal or inhibitory neuron activation. Therefore, we optogenetically activated pyramidal or PV neurons in the deep layers of cortical area V1 and measured the SNR and RF area in nearby pyramidal neurons. Activation of pyramidal or PV neurons increased the SNR by 267% and 318%, respectively, and reduced the RF area to 60.1% and 77.5%, respectively, of that of the control. A simple integrate-and-fire neuron model demonstrated that an improved SNR and a reduced RF area can increase the amount of information encoded by neurons. We conclude that in V1 activation of pyramidal neurons improves visual information processing since the location of the visual stimulus can be pinpointed more accurately (via a reduced RF area), and more information is encoded by neurons (due to increased SNR).
Assuntos
Estimulação Luminosa , Células Piramidais , Córtex Visual , Animais , Células Piramidais/fisiologia , Ratos , Córtex Visual/fisiologia , Córtex Visual/citologia , Masculino , Percepção Visual/fisiologia , Parvalbuminas/metabolismo , Razão Sinal-Ruído , Optogenética , Interneurônios/fisiologia , Córtex Visual Primário/fisiologiaRESUMO
In the mammalian neocortex, inhibition is important for dynamically balancing excitation and shaping the response properties of cells and circuits. The various computational functions of inhibition are thought to be mediated by different inhibitory neuron types, of which a large diversity exists in several species. Current understanding of the function and connectivity of distinct inhibitory neuron types has mainly derived from studies in transgenic mice. However, it is unknown whether knowledge gained from mouse studies applies to the non-human primate, the model system closest to humans. The lack of viral tools to selectively access inhibitory neuron types has been a major impediment to studying their function in the primate. Here, we have thoroughly validated and characterized several recently developed viral vectors designed to restrict transgene expression to GABAergic cells or their parvalbumin (PV) subtype, and identified two types that show high specificity and efficiency in marmoset V1. We show that in marmoset V1, AAV-h56D induces transgene expression in GABAergic cells with up to 91-94% specificity and 79% efficiency, but this depends on viral serotype and cortical layer. AAV-PHP.eB-S5E2 induces transgene expression in PV cells across all cortical layers with up to 98% specificity and 86-90% efficiency, depending on layer. Thus, these viral vectors are promising tools for studying GABA and PV cell function and connectivity in the primate cortex.
Assuntos
Callithrix , Neurônios GABAérgicos , Vetores Genéticos , Interneurônios , Parvalbuminas , Animais , Parvalbuminas/metabolismo , Parvalbuminas/genética , Neurônios GABAérgicos/metabolismo , Interneurônios/metabolismo , Dependovirus/genética , Córtex Visual Primário/metabolismo , Expressão Gênica , Transgenes , Córtex Visual/metabolismo , Córtex Visual/fisiologia , Córtex Visual/virologiaRESUMO
The lightness of a surface depends not only on the amount of light reflected off, it but also on the context in which it is embedded. Despite a long history of research, neural correlates of context-dependent lightness perception remain a topic of ongoing debate. Here, we seek to expand on the existing literature by measuring functional magnetic resonance imaging (fMRI) responses to lightness variations induced by the context. During the fMRI experiment, we presented 10 participants with a dynamic stimulus in which either the luminance of a disk or its surround is modulated at four different frequencies ranging from 1 to 8 Hz. Behaviorally, when the surround luminance is modulated at low frequencies, participants perceive an illusory change in the lightness of the disk (lightness induction). In contrast, they perceive little or no induction at higher frequencies. Using this frequency dependence and controlling for long-range responses to border contrast and luminance changes, we found that activity in the primary visual cortex (V1) correlates with lightness induction, providing further evidence for the involvement of V1 in the processing of context-dependent lightness.
Assuntos
Sensibilidades de Contraste , Imageamento por Ressonância Magnética , Estimulação Luminosa , Humanos , Imageamento por Ressonância Magnética/métodos , Adulto , Masculino , Estimulação Luminosa/métodos , Feminino , Sensibilidades de Contraste/fisiologia , Adulto Jovem , Córtex Visual Primário/fisiologia , Córtex Visual/fisiologia , LuzRESUMO
Conscious reportability of visual input is associated with a bimodal neural response in the primary visual cortex (V1): an early-latency response coupled to stimulus features and a late-latency response coupled to stimulus report or detection. This late wave of activity, central to major theories of consciousness, is thought to be driven by the prefrontal cortex (PFC), responsible for "igniting" it. Here we analyzed two electrophysiological studies in mice performing different stimulus detection tasks and characterized neural activity profiles in three key cortical regions: V1, posterior parietal cortex (PPC), and PFC. We then developed a minimal network model, constrained by known connectivity between these regions, reproducing the spatiotemporal propagation of visual- and report-related activity. Remarkably, while PFC was indeed necessary to generate report-related activity in V1, this occurred only through the mediation of PPC. PPC, and not PFC, had the final veto in enabling the report-related late wave of V1 activity.
Assuntos
Córtex Pré-Frontal , Animais , Córtex Pré-Frontal/fisiologia , Masculino , Camundongos Endogâmicos C57BL , Lobo Parietal/fisiologia , Estimulação Luminosa/métodos , Camundongos , Modelos Neurológicos , Córtex Visual Primário/fisiologia , Percepção Visual/fisiologia , Córtex Visual/fisiologia , Feminino , Neurônios/fisiologia , Retroalimentação Fisiológica/fisiologiaRESUMO
Human primary visual cortex (V1) responds more strongly, or resonates, when exposed to â¼10, â¼15-20, and â¼40-50 Hz rhythmic flickering light. Full-field flicker also evokes the perception of hallucinatory geometric patterns, which mathematical models explain as standing-wave formations emerging from periodic forcing at resonant frequencies of the simulated neural network. However, empirical evidence for such flicker-induced standing waves in the visual cortex was missing. We recorded cortical responses to flicker in awake mice using high-spatial-resolution widefield imaging in combination with high-temporal-resolution glutamate-sensing fluorescent reporter (iGluSnFR). The temporal frequency tuning curves in the mouse V1 were similar to those observed in humans, showing a banded structure with multiple resonance peaks (8, 15, and 33 Hz). Spatially, all flicker frequencies evoked responses in V1 corresponding to retinotopic stimulus location, but some evoked additional peaks. These flicker-induced cortical patterns displayed standing-wave characteristics and matched linear wave equation solutions in an area restricted to the visual cortex. Taken together, the interaction of periodic traveling waves with cortical area boundaries leads to spatiotemporal activity patterns that may affect perception.
Assuntos
Córtex Visual Primário , Animais , Camundongos , Córtex Visual Primário/fisiologia , Masculino , Estimulação Luminosa , Camundongos Endogâmicos C57BL , Feminino , Percepção Visual/fisiologia , Córtex Visual/fisiologiaRESUMO
The cerebral cortex accounts for substantial energy expenditure, primarily driven by the metabolic demands of synaptic signaling. Mitochondria, the organelles responsible for generating cellular energy, play a crucial role in this process. We investigated ultrastructural characteristics of the primary visual cortex in 18 phylogenetically diverse mammals, spanning a broad range of brain sizes from mouse to elephant. Our findings reveal remarkable uniformity in synapse density, postsynaptic density (PSD) length, and mitochondria density, indicating functional and metabolic constraints that maintain these fundamental features. Notably, we observed an average of 1.9 mitochondria per synapse across mammalian species. When considered together with the trend of decreasing neuron density with larger brain size, we find that brain enlargement in mammals is characterized by increasing proportions of synapses and mitochondria per cortical neuron. These results shed light on the adaptive mechanisms and metabolic dynamics that govern cortical ultrastructure across mammals.
Assuntos
Mamíferos , Mitocôndrias , Córtex Visual Primário , Sinapses , Animais , Sinapses/ultraestrutura , Sinapses/metabolismo , Mitocôndrias/ultraestrutura , Mitocôndrias/metabolismo , Córtex Visual Primário/fisiologia , Metabolismo Energético/fisiologia , Especificidade da Espécie , Córtex Visual/metabolismo , Córtex Visual/citologia , Córtex Visual/fisiologia , Córtex Visual/ultraestrutura , Camundongos , HumanosRESUMO
Color is an important visual feature that informs behavior, and the retinal basis for color vision has been studied across various vertebrate species. While many studies have investigated how color information is processed in visual brain areas of primate species, we have limited understanding of how it is organized beyond the retina in other species, including most dichromatic mammals. In this study, we systematically characterized how color is represented in the primary visual cortex (V1) of mice. Using large-scale neuronal recordings and a luminance and color noise stimulus, we found that more than a third of neurons in mouse V1 are color-opponent in their receptive field center, while the receptive field surround predominantly captures luminance contrast. Furthermore, we found that color-opponency is especially pronounced in posterior V1 that encodes the sky, matching the statistics of natural scenes experienced by mice. Using unsupervised clustering, we demonstrate that the asymmetry in color representations across cortex can be explained by an uneven distribution of green-On/UV-Off color-opponent response types that are represented in the upper visual field. Finally, a simple model with natural scene-inspired parametric stimuli shows that green-On/UV-Off color-opponent response types may enhance the detection of 'predatory'-like dark UV-objects in noisy daylight scenes. The results from this study highlight the relevance of color processing in the mouse visual system and contribute to our understanding of how color information is organized in the visual hierarchy across species.
Assuntos
Visão de Cores , Córtex Visual , Animais , Camundongos , Visão de Cores/fisiologia , Córtex Visual/fisiologia , Percepção de Cores/fisiologia , Estimulação Luminosa , Camundongos Endogâmicos C57BL , Neurônios/fisiologia , Córtex Visual Primário/fisiologia , MasculinoRESUMO
The brain functions as a prediction machine, utilizing an internal model of the world to anticipate sensations and the outcomes of our actions. Discrepancies between expected and actual events, referred to as prediction errors, are leveraged to update the internal model and guide our attention towards unexpected events1-10. Despite the importance of prediction-error signals for various neural computations across the brain, surprisingly little is known about the neural circuit mechanisms responsible for their implementation. Here we describe a thalamocortical disinhibitory circuit that is required for generating sensory prediction-error signals in mouse primary visual cortex (V1). We show that violating animals' predictions by an unexpected visual stimulus preferentially boosts responses of the layer 2/3 V1 neurons that are most selective for that stimulus. Prediction errors specifically amplify the unexpected visual input, rather than representing non-specific surprise or difference signals about how the visual input deviates from the animal's predictions. This selective amplification is implemented by a cooperative mechanism requiring thalamic input from the pulvinar and cortical vasoactive-intestinal-peptide-expressing (VIP) inhibitory interneurons. In response to prediction errors, VIP neurons inhibit a specific subpopulation of somatostatin-expressing inhibitory interneurons that gate excitatory pulvinar input to V1, resulting in specific pulvinar-driven response amplification of the most stimulus-selective neurons in V1. Therefore, the brain prioritizes unpredicted sensory information by selectively increasing the salience of unpredicted sensory features through the synergistic interaction of thalamic input and neocortical disinhibitory circuits.
Assuntos
Interneurônios , Córtex Visual Primário , Tálamo , Peptídeo Intestinal Vasoativo , Animais , Camundongos , Masculino , Peptídeo Intestinal Vasoativo/metabolismo , Interneurônios/fisiologia , Feminino , Tálamo/fisiologia , Tálamo/citologia , Córtex Visual Primário/fisiologia , Córtex Visual Primário/citologia , Pulvinar/fisiologia , Pulvinar/citologia , Modelos Neurológicos , Estimulação Luminosa , Inibição Neural/fisiologia , Somatostatina/metabolismo , Camundongos Endogâmicos C57BL , Córtex Visual/fisiologia , Córtex Visual/citologia , Vias Visuais/fisiologiaRESUMO
A key feature of neurons in the primary visual cortex (V1) of primates is their orientation selectivity. Recent studies using deep neural network models showed that the most exciting input (MEI) for mouse V1 neurons exhibit complex spatial structures that predict non-uniform orientation selectivity across the receptive field (RF), in contrast to the classical Gabor filter model. Using local patches of drifting gratings, we identified heterogeneous orientation tuning in mouse V1 that varied up to 90° across sub-regions of the RF. This heterogeneity correlated with deviations from optimal Gabor filters and was consistent across cortical layers and recording modalities (calcium vs. spikes). In contrast, model-synthesized MEIs for macaque V1 neurons were predominantly Gabor like, consistent with previous studies. These findings suggest that complex spatial feature selectivity emerges earlier in the visual pathway in mice than in primates. This may provide a faster, though less general, method of extracting task-relevant information.
Assuntos
Córtex Visual Primário , Animais , Camundongos , Córtex Visual Primário/fisiologia , Orientação/fisiologia , Camundongos Endogâmicos C57BL , Neurônios/fisiologia , Estimulação Luminosa , Masculino , Campos Visuais/fisiologia , Córtex Visual/fisiologia , Vias Visuais/fisiologia , PrimatasRESUMO
Knowledge integration based on the relationship between structure and function of the neural substrate is one of the main targets of neuroinformatics and data-driven computational modeling. However, the multiplicity of data sources, the diversity of benchmarks, the mixing of observables of different natures, and the necessity of a long-term, systematic approach make such a task challenging. Here we present a first snapshot of a long-term integrative modeling program designed to address this issue in the domain of the visual system: a comprehensive spiking model of cat primary visual cortex. The presented model satisfies an extensive range of anatomical, statistical and functional constraints under a wide range of visual input statistics. In the presence of physiological levels of tonic stochastic bombardment by spontaneous thalamic activity, the modeled cortical reverberations self-generate a sparse asynchronous ongoing activity that quantitatively matches a range of experimentally measured statistics. When integrating feed-forward drive elicited by a high diversity of visual contexts, the simulated network produces a realistic, quantitatively accurate interplay between visually evoked excitatory and inhibitory conductances; contrast-invariant orientation-tuning width; center surround interactions; and stimulus-dependent changes in the precision of the neural code. This integrative model offers insights into how the studied properties interact, contributing to a better understanding of visual cortical dynamics. It provides a basis for future development towards a comprehensive model of low-level perception.
Assuntos
Biologia Computacional , Modelos Neurológicos , Córtex Visual Primário , Gatos , Animais , Córtex Visual Primário/fisiologia , Potenciais de Ação/fisiologia , Simulação por Computador , Córtex Visual/fisiologia , Neurônios/fisiologiaRESUMO
Using anti-neurofilament H non-phosphorylated antibodies (SMI-32) as markers for the neuronal maturation level and Y channel responsible for motion processing, we investigated early postnatal development of the primary visual areas 17 and 18 in cats aged 0, 10, 14, and 34 days and in adults. Two analyzed parameters of SMI-32-immunolabeling were used: the total proportion of SMI-32-labeling and the density of labeled neurons. (i) The developmental time course of the total proportion of SMI-32-labeling shows the general increase in the accumulation of heavy-chain neurofilaments. This parameter showed a different time course for cortical layer development; the maximal increment in the total labeling in layer V occurred between the second and fifth postnatal weeks and in layers II-III and VI after the fifth postnatal week. In addition, the delay in accumulation of SMI-32-labeling was shown in layer V of the area 17 periphery representation during the first two postnatal weeks. (ii) The density of SMI-32-labeled neurons decreased in all layers of area 18, but was increased, decreased, or had a transient peak in layers II-III, V, and VI of area 17, respectively. The transient peak is in good correspondence with some transient neurochemical features previously revealed for different classes of cortical and thalamic neurons and reflects the time course of the early development of the thalamocortical circuitry. Some similarities between the time courses for the development of SMI-32-labeling in areas 17/18 and in A- and C-laminae of the LGNd allow us to propose heterochronous postnatal development of two Y sub-channels.
Assuntos
Animais Recém-Nascidos , Proteínas de Neurofilamentos , Neurônios , Animais , Gatos , Proteínas de Neurofilamentos/metabolismo , Neurônios/metabolismo , Córtex Visual Primário/crescimento & desenvolvimento , Córtex Visual Primário/fisiologiaRESUMO
White matter (WM) functional activity has been reliably detected through functional magnetic resonance imaging (fMRI). Previous studies have primarily examined WM bundles as unified entities, thereby obscuring the functional heterogeneity inherent within these bundles. Here, for the first time, we investigate the function of sub-bundles of a prototypical visual WM tract-the optic radiation (OR). We use the 7T retinotopy dataset from the Human Connectome Project (HCP) to reconstruct OR and further subdivide the OR into sub-bundles based on the fiber's termination in the primary visual cortex (V1). The population receptive field (pRF) model is then applied to evaluate the retinotopic properties of these sub-bundles, and the consistency of the pRF properties of sub-bundles with those of V1 subfields is evaluated. Furthermore, we utilize the HCP working memory dataset to evaluate the activations of the foveal and peripheral OR sub-bundles, along with LGN and V1 subfields, during 0-back and 2-back tasks. We then evaluate differences in 2bk-0bk contrast between foveal and peripheral sub-bundles (or subfields), and further examine potential relationships between 2bk-0bk contrast and 2-back task d-prime. The results show that the pRF properties of OR sub-bundles exhibit standard retinotopic properties and are typically similar to the properties of V1 subfields. Notably, activations during the 2-back task consistently surpass those under the 0-back task across foveal and peripheral OR sub-bundles, as well as LGN and V1 subfields. The foveal V1 displays significantly higher 2bk-0bk contrast than peripheral V1. The 2-back task d-prime shows strong correlations with 2bk-0bk contrast for foveal and peripheral OR fibers. These findings demonstrate that the blood oxygen level-dependent (BOLD) signals of OR sub-bundles encode high-fidelity visual information, underscoring the feasibility of assessing WM functional activity at the sub-bundle level. Additionally, the study highlights the role of OR in the top-down processes of visual working memory beyond the bottom-up processes for visual information transmission. Conclusively, this study innovatively proposes a novel paradigm for analyzing WM fiber tracts at the individual sub-bundle level and expands understanding of OR function.
Assuntos
Conectoma , Imageamento por Ressonância Magnética , Memória de Curto Prazo , Vias Visuais , Humanos , Memória de Curto Prazo/fisiologia , Conectoma/métodos , Vias Visuais/fisiologia , Vias Visuais/diagnóstico por imagem , Adulto , Masculino , Feminino , Percepção Visual/fisiologia , Substância Branca/diagnóstico por imagem , Substância Branca/fisiologia , Substância Branca/anatomia & histologia , Córtex Visual Primário/fisiologia , Córtex Visual Primário/diagnóstico por imagem , Corpos Geniculados/fisiologia , Corpos Geniculados/diagnóstico por imagem , Adulto Jovem , Córtex Visual/fisiologia , Córtex Visual/diagnóstico por imagemRESUMO
The local field potential (LFP) is as a measure of the combined activity of neurons within a region of brain tissue. While biophysical modeling schemes for LFP in cortical circuits are well established, there is a paramount lack of understanding regarding the LFP properties along the states assumed in cortical circuits over long periods. Here we use a symbolic information approach to determine the statistical complexity based on Jensen disequilibrium measure and Shannon entropy of LFP data recorded from the primary visual cortex (V1) of urethane-anesthetized rats and freely moving mice. Using these information quantifiers, we find consistent relations between LFP recordings and measures of cortical states at the neuronal level. More specifically, we show that LFP's statistical complexity is sensitive to cortical state (characterized by spiking variability), as well as to cortical layer. In addition, we apply these quantifiers to characterize behavioral states of freely moving mice, where we find indirect relations between such states and spiking variability.
Assuntos
Modelos Neurológicos , Córtex Visual Primário , Animais , Camundongos , Ratos , Córtex Visual Primário/fisiologia , Córtex Visual Primário/citologia , Potenciais de Ação , Neurônios/fisiologia , Córtex Visual/fisiologia , Córtex Visual/citologiaRESUMO
Visual cortical neurons show variability in their responses to repeated presentations of a stimulus and a portion of this variability is shared across neurons. Attention may enhance visual perception by reducing shared spiking variability. However, shared variability and its attentional modulation are not consistent within or across cortical areas, and depend on additional factors such as neuronal type. A critical factor that has not been tested is actual anatomical connectivity. We measured spike count correlations among pairs of simultaneously recorded neurons in the primary visual cortex (V1) for which anatomical connectivity was inferred from spiking cross-correlations. Neurons were recorded in monkeys performing a contrast-change discrimination task requiring covert shifts in visual spatial attention. Accordingly, spike count correlations were compared across trials in which attention was directed toward or away from the visual stimulus overlapping recorded neuronal receptive fields. Consistent with prior findings, attention did not significantly alter spike count correlations among random pairings of unconnected V1 neurons. However, V1 neurons connected via excitatory synapses showed a significant reduction in spike count correlations with attention. Interestingly, V1 neurons connected via inhibitory synapses demonstrated high spike count correlations overall that were not modulated by attention. Correlated variability in excitatory circuits also depended upon neuronal tuning for contrast, the task-relevant stimulus feature. These results indicate that shared variability depends on the type of connectivity in neuronal circuits. Also, attention significantly reduces shared variability in excitatory circuits, even when attention effects on randomly sampled neurons within the same area are weak.
Assuntos
Atenção , Macaca mulatta , Neurônios , Animais , Atenção/fisiologia , Neurônios/fisiologia , Percepção Visual/fisiologia , Córtex Visual/fisiologia , Masculino , Estimulação Luminosa , Córtex Visual Primário/fisiologia , Potenciais de Ação/fisiologia , Sinapses/fisiologiaRESUMO
Perceptual learning refers to any change in discrimination abilities as a result of practice, a fundamental process that improves the organism's response to the external environment. Visual perceptual learning (vPL) is supposed to rely on functional rearrangements in brain circuity occurring at early stages of sensory processing, with a pivotal role for the primary visual cortex (V1). However, top-down inputs from higher-order visual areas (HVAs) have been suggested to play a key part in vPL, conveying information on attention, expectation and the precise nature of the perceptual task. A direct assessment of the possibility to modulate vPL by manipulating top-down activity in awake subjects is still missing. Here, we used a combination of chemogenetics, behavioral analysis and multichannel electrophysiological assessments to show a critical role in vPL acquisition and retention for neuronal activity in the latero-medial secondary visual cortex (LM), the prime source for top-down feedback projections reentering V1.
Assuntos
Aprendizagem , Córtex Visual , Percepção Visual , Córtex Visual/fisiologia , Animais , Percepção Visual/fisiologia , Aprendizagem/fisiologia , Camundongos , Masculino , Camundongos Endogâmicos C57BL , Estimulação Luminosa , Neurônios/fisiologia , Feminino , Córtex Visual Primário/fisiologiaRESUMO
The study of the neural substrates that serve conscious vision is one of the unsolved questions of cognitive neuroscience. So far, consciousness literature has endeavoured to disentangle which brain areas and in what order are involved in giving rise to visual awareness, but the problem of consciousness still remains unsolved. Availing of two different but complementary sources of data (i.e., Fast Optical Imaging and EEG), we sought to unravel the neural dynamics responsible for the emergence of a conscious visual experience. Our results revealed that conscious vision is characterized by a significant increase of activation in extra-striate visual areas, specifically in the Lateral Occipital Complex (LOC), and that, more interestingly, such activity occurred in the temporal window of the ERP component commonly thought to represent the electrophysiological signature of visual awareness, i.e., the Visual Awareness Negativity (VAN). Furthermore, Granger causality analysis, performed to further investigate the flow of activity occurring in the investigated areas, unveiled that neural processes relating to conscious perception mainly originated in LOC and subsequently spread towards visual and motor areas. In general, the results of the present study seem to advocate for an early contribution of LOC in conscious vision, thus suggesting that it could represent a reliable neural correlate of visual awareness. Conversely, striate visual areas, showing awareness-related activity only in later stages of stimulus processing, could be part of the cascade of neural events following awareness emergence.
Assuntos
Estado de Consciência , Eletroencefalografia , Lobo Occipital , Percepção Visual , Humanos , Estado de Consciência/fisiologia , Percepção Visual/fisiologia , Masculino , Feminino , Adulto , Adulto Jovem , Lobo Occipital/fisiologia , Lobo Occipital/diagnóstico por imagem , Córtex Visual Primário/fisiologia , Córtex Visual Primário/diagnóstico por imagem , Mapeamento Encefálico , Potenciais Evocados Visuais/fisiologia , Córtex Visual/fisiologia , Córtex Visual/diagnóstico por imagem , Conscientização/fisiologiaRESUMO
The primary visual cortex (V1) in blindness is engaged in a wide spectrum of tasks and sensory modalities, including audition, touch, language, and memory. This widespread involvement raises questions regarding the constancy of its role and whether it might exhibit flexibility in its function over time, connecting to diverse network functions specific to task demands. This would suggest that reorganized V1 assumes a role like multiple-demand system regions. Alternatively, varying patterns of plasticity in blind V1 may be attributed to individual factors, with different blind individuals recruiting V1 preferentially for different functions. In support of this, we recently showed that V1 functional connectivity (FC) varies greatly across blind individuals. But do these represent stable individual patterns of plasticity, or are they driven more by instantaneous changes, like a multiple-demand system now inhabiting V1? Here, we tested whether individual FC patterns from the V1 of blind individuals are stable over time. We show that over two years, FC from the V1 is unique and highly stable in a small sample of repeatedly sampled congenitally blind individuals. Further, using multivoxel pattern analysis, we demonstrate that the unique reorganization patterns of these individuals allow decoding of participant identity. Together with recent evidence for substantial individual differences in V1 connectivity, this indicates that there may be a consistent role for V1 in blindness, which may differ for each individual. Further, it suggests that the variability in visual reorganization in blindness across individuals could be used to seek stable neuromarkers for sight rehabilitation and assistive approaches.
Assuntos
Cegueira , Plasticidade Neuronal , Humanos , Cegueira/fisiopatologia , Plasticidade Neuronal/fisiologia , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Imageamento por Ressonância Magnética , Córtex Visual Primário/fisiologia , Estudos Longitudinais , Córtex Visual/fisiopatologia , Córtex Visual/fisiologia , Córtex Visual/diagnóstico por imagem , Mapeamento Encefálico/métodosRESUMO
Patients with post-traumatic stress disorder (PTSD) exhibit sex differences in symptomology, with women more likely to report higher rates of intrusive and avoidance symptoms than men, underscoring the need for sex-informed approaches to research and treatment. Our study delved into the sex-specific aspects of stress-induced visual impairments using the single prolonged stress (SPS) model, a partially validated rodent model for PTSD. Male SPS mice exhibit heightened optimal spatial frequency (SF) of primary visual cortex (V1) neurons, while female counterparts exhibit decreased optimal temporal frequency (TF) of V1 neurons. This phenomenon persisted until the 29th day after SPS modeling, and it may be the physiological basis for the observed increase in visual acuity in male SPS mice in visual water task. Furthermore, our study found that corticotropin-releasing factor receptor 1 regulated optimal TF and optimal SF of V1 in mice, but did not exhibit sex differences. These findings indicated that severe stress induces sex-specific effects on visual function.
Assuntos
Modelos Animais de Doenças , Camundongos Endogâmicos C57BL , Receptores de Hormônio Liberador da Corticotropina , Caracteres Sexuais , Estresse Psicológico , Animais , Masculino , Feminino , Estresse Psicológico/fisiopatologia , Estresse Psicológico/psicologia , Receptores de Hormônio Liberador da Corticotropina/metabolismo , Camundongos , Neurônios/fisiologia , Transtornos de Estresse Pós-Traumáticos/fisiopatologia , Transtornos de Estresse Pós-Traumáticos/psicologia , Córtex Visual Primário/fisiologia , Acuidade Visual/fisiologia , Córtex VisualRESUMO
N, N-dimethyltryptamine (DMT) is a psychedelic tryptamine acting on 5-HT2A serotonin receptors, which is associated with intense visual hallucinatory phenomena and perceptual changes such as distortions in visual space. The neural underpinnings of these effects remain unknown. We hypothesised that changes in population receptive field (pRF) properties in the primary visual cortex (V1) might underlie visual perceptual experience. We tested this hypothesis using magnetic resonance imaging (MRI) in a within-subject design. We used a technique called pRF mapping, which measures neural population visual response properties and retinotopic maps in early visual areas. We show that in the presence of visual effects, as documented by the Hallucinogen Rating Scale (HRS), the mean pRF sizes in V1 significantly increase in the peripheral visual field for active condition (inhaled DMT) compared to the control. Eye and head movement differences were absent across conditions. This evidence for short-term effects of DMT in pRF may explain perceptual distortions induced by psychedelics such as field blurring, tunnel vision (peripheral vision becoming blurred while central vision remains sharp) and the enlargement of nearby visual space, particularly at the visual locations surrounding the fovea. Our findings are also consistent with a mechanistic framework whereby gain control of ongoing and evoked activity in the visual cortex is controlled by activation of 5-HT2A receptors.