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1.
Brain ; 147(1): 56-80, 2024 01 04.
Artigo em Inglês | MEDLINE | ID: mdl-37703310

RESUMO

Integrating independent but converging lines of research on brain function and neurodevelopment across scales, this article proposes that serotonin 2A receptor (5-HT2AR) signalling is an evolutionary and developmental driver and potent modulator of the macroscale functional organization of the human cerebral cortex. A wealth of evidence indicates that the anatomical and functional organization of the cortex follows a unimodal-to-transmodal gradient. Situated at the apex of this processing hierarchy-where it plays a central role in the integrative processes underpinning complex, human-defining cognition-the transmodal cortex has disproportionately expanded across human development and evolution. Notably, the adult human transmodal cortex is especially rich in 5-HT2AR expression and recent evidence suggests that, during early brain development, 5-HT2AR signalling on neural progenitor cells stimulates their proliferation-a critical process for evolutionarily-relevant cortical expansion. Drawing on multimodal neuroimaging and cross-species investigations, we argue that, by contributing to the expansion of the human cortex and being prevalent at the apex of its hierarchy in the adult brain, 5-HT2AR signalling plays a major role in both human cortical expansion and functioning. Owing to its unique excitatory and downstream cellular effects, neuronal 5-HT2AR agonism promotes neuroplasticity, learning and cognitive and psychological flexibility in a context-(hyper)sensitive manner with therapeutic potential. Overall, we delineate a dual role of 5-HT2ARs in enabling both the expansion and modulation of the human transmodal cortex.


Assuntos
Córtex Cerebral , Receptor 5-HT2A de Serotonina , Adulto , Humanos , Encéfalo , Córtex Cerebral/fisiologia , Cognição/fisiologia , Neuroimagem
2.
Proc Natl Acad Sci U S A ; 119(3)2022 01 18.
Artigo em Inglês | MEDLINE | ID: mdl-35027449

RESUMO

Inferotemporal (IT) cortex in humans and other primates is topographically organized, containing multiple hierarchically organized areas selective for particular domains, such as faces and scenes. This organization is commonly viewed in terms of evolved domain-specific visual mechanisms. Here, we develop an alternative, domain-general and developmental account of IT cortical organization. The account is instantiated in interactive topographic networks (ITNs), a class of computational models in which a hierarchy of model IT areas, subject to biologically plausible connectivity-based constraints, learns high-level visual representations optimized for multiple domains. We find that minimizing a wiring cost on spatially organized feedforward and lateral connections, alongside realistic constraints on the sign of neuronal connectivity within model IT, results in a hierarchical, topographic organization. This organization replicates a number of key properties of primate IT cortex, including the presence of domain-selective spatial clusters preferentially involved in the representation of faces, objects, and scenes; columnar responses across separate excitatory and inhibitory units; and generic spatial organization whereby the response correlation of pairs of units falls off with their distance. We thus argue that topographic domain selectivity is an emergent property of a visual system optimized to maximize behavioral performance under generic connectivity-based constraints.


Assuntos
Modelos Neurológicos , Redes Neurais de Computação , Neurônios/fisiologia , Córtex Visual/fisiologia , Animais , Simulação por Computador , Primatas , Vias Visuais/fisiologia
3.
Cereb Cortex ; 33(21): 10770-10783, 2023 10 14.
Artigo em Inglês | MEDLINE | ID: mdl-37727985

RESUMO

It is well known that functional magnetic resonance imaging (fMRI) is a widely used tool for studying brain activity. Recent research has shown that fluctuations in fMRI data can reflect functionally meaningful patterns of brain activity within the white matter. We leveraged resting-state fMRI from an adolescent population to characterize large-scale white matter functional gradients and their formation during adolescence. The white matter showed gray-matter-like unimodal-to-transmodal and sensorimotor-to-visual gradients with specific cognitive associations and a unique superficial-to-deep gradient with nonspecific cognitive associations. We propose two mechanisms for their formation in adolescence. One is a "function-molded" mechanism that may mediate the maturation of the transmodal white matter via the transmodal gray matter. The other is a "structure-root" mechanism that may support the mutual mediation roles of the unimodal and transmodal white matter maturation during adolescence. Thus, the spatial layout of the white matter functional gradients is in concert with the gray matter functional organization. The formation of the white matter functional gradients may be driven by brain anatomical wiring and functional needs.


Assuntos
Substância Branca , Adolescente , Humanos , Substância Branca/patologia , Encéfalo/diagnóstico por imagem , Encéfalo/patologia , Substância Cinzenta/patologia , Imageamento por Ressonância Magnética , Mapeamento Encefálico/métodos
4.
Scand J Med Sci Sports ; 34(9): e14726, 2024 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-39263841

RESUMO

Patellar tendinopathy (PT) typically affects jumping-sport athletes with functional impairments frequently observed. Alterations to the functional organization of corticomotor neurons within the motor cortex that project to working muscles are evident in some musculoskeletal conditions and linked to functional impairments. We aimed to determine if functional organization of corticomotor neuron projections differs between athletes with PT and asymptomatic controls, and if organization is associated with neuromuscular control. We used a cross-sectional design, and the setting was Monash Biomedical Imaging. Basketball and volleyball athletes with (n = 8) and without PT (n = 8) completed knee extension and ankle dorsiflexion force matching tasks while undergoing fMRI. We determined functional organization via identification of the location of peak corticomotor neuron activation during respective tasks (expressed in X, Y, and Z coordinates) and calculated force matching accuracy for both tasks to quantify neuromuscular control. We observed significant interactions between group and coordinate plane for functional organization of corticomotor projections to knee extensors (p < 0.001) and ankle dorsiflexors (p = 0.016). Compared to controls, PT group peak corticomotor activation during the knee extension task was 9.6 mm medial (p < 0.001) and 5.2 mm posterior (p = 0.036), and during the ankle dorsiflexion task 8.2 mm inferior (p = 0.024). In the PT group, more posterior Y coordinate peak activation location during the knee extension task was associated with greater task accuracy (r = 0.749, p = 0.034). Functional organization of corticomotor neurons differed in jumping athletes with PT compared to controls. Links between functional organization and neuromuscular control in the PT group suggest organizational differences may be relevant to knee extension neuromuscular control preservation.


Assuntos
Basquetebol , Imageamento por Ressonância Magnética , Córtex Motor , Tendinopatia , Voleibol , Humanos , Voleibol/fisiologia , Basquetebol/fisiologia , Córtex Motor/fisiologia , Córtex Motor/fisiopatologia , Estudos Transversais , Tendinopatia/fisiopatologia , Masculino , Adulto Jovem , Feminino , Adulto , Neurônios Motores/fisiologia , Ligamento Patelar/fisiopatologia , Ligamento Patelar/fisiologia , Atletas , Estudos de Casos e Controles
5.
Hippocampus ; 32(11-12): 839-856, 2022 11.
Artigo em Inglês | MEDLINE | ID: mdl-36314648

RESUMO

Memory is vital to our daily existence. Although a large number of studies have suggested that the hippocampus is dedicated to long-term memory, understanding how memory is anatomically encoded within the hippocampal neuronal network is still lacking. Previously our laboratory showed that hippocampal pyramidal cells are organized in cell clusters to encode both spatial and episodic memory. Based on these findings, we hypothesized that "cluster-type" is a functional organization principal in the hippocampus to encode all types of memory. Here, we tested whether contextual fear, another hippocampus-dependent memory, is also organized in cell clusters. We further investigated the possibility that post-learning sleep may affect functional organization. Cluster formation was examined by assessing the topographic localization of active cells using immediate early gene (IEG, Zif268) imaging methods. The first experiment provides evidence of a cluster-type organization in the hippocampus for fear memory by showing a spatial distribution of adjacent Zif268 positive cells. Exposure to the context itself, without electric shocks, induced a similar cellular formation; however, the degree of clustering was significantly lower. The second experiment provides evidence that sleep plays a role in the refinement and long-term stability of the clusters. The present results confirm the existence of a cluster-type topographic functional neuronal organization in the hippocampus for memory, and further suggest that post-learning sleep enhances the cluster-type organization.


Assuntos
Proteína 1 de Resposta de Crescimento Precoce , Hipocampo , Proteína 1 de Resposta de Crescimento Precoce/metabolismo , Hipocampo/fisiologia , Medo/fisiologia , Genes Precoces , Sono
6.
Neuroimage ; 225: 117528, 2021 01 15.
Artigo em Inglês | MEDLINE | ID: mdl-33157264

RESUMO

Understanding cortical organization is a fundamental goal of neuroscience that requires comparisons across species and modalities. Large-scale connectivity gradients have recently been introduced as a data-driven representation of the intrinsic organization of the cortex. We studied resting-state functional connectivity gradients in the mouse cortex and found robust spatial patterns across four data sets. The principal gradient of functional connectivity shows a striking overlap with an axis of neocortical evolution from two primordial origins. Additional gradients reflect sensory specialization and aspects of a sensory-to-transmodal hierarchy, and are associated with transcriptomic features. While some of these gradients strongly resemble observations in the human cortex, the overall pattern in the mouse cortex emphasizes the specialization of sensory areas over a global functional hierarchy.


Assuntos
Evolução Biológica , Neocórtex/diagnóstico por imagem , Vias Neurais/diagnóstico por imagem , Animais , Mapeamento Encefálico , Córtex Cerebral/diagnóstico por imagem , Córtex Cerebral/fisiologia , Conectoma , Neuroimagem Funcional , Imageamento por Ressonância Magnética , Camundongos , Camundongos Endogâmicos C57BL , Neocórtex/fisiologia , Vias Neurais/fisiologia , Descanso
7.
Cereb Cortex ; 30(5): 3313-3324, 2020 05 14.
Artigo em Inglês | MEDLINE | ID: mdl-32080708

RESUMO

The corpus callosum is the commissural bridge of white-matter bundles important for the human brain functions. Previous studies have analyzed the structural links between cortical gray-matter networks and subregions of corpus callosum. While meaningful white-matter functional networks (WM-FNs) were recently reported, how these networks functionally link with distinct subregions of corpus callosum remained unknown. The current study used resting-state functional magnetic resonance imaging of the Human Connectome Project test-retest data to identify 10 cerebral WM-FNs in 119 healthy subjects and then parcellated the corpus callosum into distinct subregions based on the functional connectivity between each callosal voxel and above networks. Our results demonstrated the reproducible identification of WM-FNs and their links with known gray-matter functional networks across two runs. Furthermore, we identified reliably parcellated subregions of the corpus callosum, which might be involved in primary and higher order functional systems by functionally connecting with WM-FNs. The current study extended our knowledge about the white-matter functional signals to the intrinsic functional organization of human corpus callosum, which could help researchers understand the neural substrates underlying normal interhemispheric functional connectivity as well as dysfunctions in various mental disorders.


Assuntos
Conectoma , Corpo Caloso/diagnóstico por imagem , Substância Branca/diagnóstico por imagem , Encéfalo/diagnóstico por imagem , Encéfalo/fisiologia , Corpo Caloso/fisiologia , Neuroimagem Funcional , Voluntários Saudáveis , Humanos , Imageamento por Ressonância Magnética , Vias Neurais , Substância Branca/fisiologia
8.
J Physiol ; 598(5): 1039-1072, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-31943205

RESUMO

KEY POINTS: In the central nucleus of the inferior colliculus (ICC), which acts as the hub of the auditory pathways, how the sound is coded by distinct cell types is largely unknown. Large GABAergic cells are tuned broadly to pure tones and respond more strongly to frequency-modulated sweeps than small GABAergic and glutamatergic (GLU) cells. Neurons, especially GLU cells, which share sharpness of tuning and sweep sensitivity, were spatially clustered inside the ICC. The difference in responsiveness between cell types was partially explained by the morphology of dendritic trees and the spatial distributions of excitatory and inhibitory inputs. The results suggest that each ICC cell type has a particular sound-encoding strategy, which is partially determined by the morphological characteristics and location of cells, and contributes information coding in higher centres in different ways. ABSTRACT: The rules governing the encoding of sound information in the higher auditory centres are largely unknown. In the central nucleus of the inferior colliculus (ICC), which acts as the hub of the auditory pathways, the presence of functional maps other than tonotopicity has been suggested but not established, due to significant heterogeneity in the response properties of single microdomains. Since each ICC cell type has distinct neuronal circuitry, each cell type might encode sound information differently. Here, juxtacellular recording from rat ICC of both sexes revealed that large GABAergic (LG), small GABAergic (SG) and glutamatergic (GLU) cells encode sound information differently. LG cells are broadly tuned and respond more strongly to frequency-modulated sweeps than SG and GLU cells. At a population level, responsiveness to sweeps is location dependent: the responsiveness to sweeps is shared in local clusters of GLU cells, whereas that to directional selectivity of sweeps is shared in local clusters of LG cells. The difference in responsiveness between cell types was partially explained by the morphology of dendritic trees and the spatial distributions of excitatory and inhibitory inputs. LG neurons had a dense local axonal plexus with projection fibres to multiple distant targets, whereas GLU projection neurons mainly aimed at a single, distant target and had less dense local collaterals. These results suggest that each ICC cell type has a particular sound-encoding strategy, which is partially determined by the morphological characteristics and location of the cell, and the different cell types contribute information coding in higher centres in different ways.


Assuntos
Colículos Inferiores , Localização de Som , Estimulação Acústica , Animais , Vias Auditivas , Feminino , Humanos , Masculino , Mesencéfalo , Ratos , Som
9.
Proc Natl Acad Sci U S A ; 114(8): 2030-2035, 2017 02 21.
Artigo em Inglês | MEDLINE | ID: mdl-28174269

RESUMO

Human prefrontal cortex supports goal-directed behavior by representing abstract information about task context. The organizational basis of these context representations, and of representations underlying other higher-order processes, is unknown. Here, we use multivariate decoding and analyses of spontaneous correlations to show that context representations are distributed across subnetworks within prefrontal cortex. Examining targeted prefrontal regions, we found that pairs of voxels with similar context preferences exhibited spontaneous correlations that were approximately twice as large as those between pairs with opposite context preferences. This subnetwork organization was stable across task-engaged and resting states, suggesting that abstract context representations are constrained by an intrinsic functional architecture. These results reveal a principle of fine-scaled functional organization in association cortex.


Assuntos
Cognição/fisiologia , Tomada de Decisões/fisiologia , Rede Nervosa/fisiologia , Córtex Pré-Frontal/fisiologia , Adulto , Mapeamento Encefálico , Biologia Computacional , Feminino , Voluntários Saudáveis , Humanos , Masculino , Análise Multivariada , Adulto Jovem
10.
J Neurophysiol ; 120(6): 2796-2805, 2018 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-30281380

RESUMO

During anticipated postural perturbations induced by limb movement, the central nervous system generates anticipatory postural adjustments (APAs) in the trunk and hip musculature to minimize disturbances to equilibrium. Age-related changes in functional organization of the nervous system may contribute to changes in APAs in healthy older adults. Here we examined if altered APAs of trunk/hip musculature in older adults are accompanied by changes in the representation of these muscles in motor cortex. Twelve healthy older adults, 5 with a history of falls and 7 nonfallers, were compared with 13 young adults. APAs were assessed during a mediolateral arm raise task in standing. Temporal organization of postural adjustments was quantified as latency of APAs in the contralateral external oblique, lumbar paraspinals, and gluteus medius relative to activation of the deltoid. Spatial organization was quantified as extent of synergistic coactivation between muscles. Volume and location of the muscle representations in motor cortex were mapped using transcranial magnetic stimulation. We found that older adults demonstrated significantly delayed APAs in the gluteus medius muscle. Spatial organization of the three muscles in motor cortex differed between groups, with the older adults demonstrating more lateral external oblique representation than the other two muscles. Separate comparisons of the faller and nonfaller subgroups with young adults indicated that nonfallers had the greatest delay in gluteus medius APAs and a reduced distance between the representational areas of the lumbar paraspinals and gluteus medius. This study indicates that altered spatial organization of motor cortex accompanies altered temporal organization of APA synergies in older adults. NEW & NOTEWORTHY Anticipatory postural adjustments are a critical component of postural control. Here we demonstrate that, in healthy older adults with and without a history of falls, delayed anticipatory postural adjustments in the hip musculature during mediolateral perturbations are accompanied by altered organization of trunk/hip muscle representation in motor cortex. The largest adaptations are evident in older adults with no history of falls.


Assuntos
Adaptação Fisiológica , Envelhecimento/fisiologia , Antecipação Psicológica , Córtex Motor/fisiologia , Equilíbrio Postural , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Masculino , Córtex Motor/crescimento & desenvolvimento , Músculo Esquelético/crescimento & desenvolvimento , Músculo Esquelético/fisiologia , Percepção Espacial
11.
Cerebellum ; 17(5): 654-682, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-29876802

RESUMO

The compartmentalization of the cerebellum into modules is often used to discuss its function. What, exactly, can be considered a module, how do they operate, can they be subdivided and do they act individually or in concert are only some of the key questions discussed in this consensus paper. Experts studying cerebellar compartmentalization give their insights on the structure and function of cerebellar modules, with the aim of providing an up-to-date review of the extensive literature on this subject. Starting with an historical perspective indicating that the basis of the modular organization is formed by matching olivocorticonuclear connectivity, this is followed by consideration of anatomical and chemical modular boundaries, revealing a relation between anatomical, chemical, and physiological borders. In addition, the question is asked what the smallest operational unit of the cerebellum might be. Furthermore, it has become clear that chemical diversity of Purkinje cells also results in diversity of information processing between cerebellar modules. An additional important consideration is the relation between modular compartmentalization and the organization of the mossy fiber system, resulting in the concept of modular plasticity. Finally, examination of cerebellar output patterns suggesting cooperation between modules and recent work on modular aspects of emotional behavior are discussed. Despite the general consensus that the cerebellum has a modular organization, many questions remain. The authors hope that this joint review will inspire future cerebellar research so that we are better able to understand how this brain structure makes its vital contribution to behavior in its most general form.


Assuntos
Cerebelo/anatomia & histologia , Cerebelo/fisiologia , Animais , Humanos
12.
J Neurosci ; 36(6): 2014-26, 2016 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-26865624

RESUMO

The human superior temporal gyrus (STG) is critical for speech perception, yet the organization of spectrotemporal processing of speech within the STG is not well understood. Here, to characterize the spatial organization of spectrotemporal processing of speech across human STG, we use high-density cortical surface field potential recordings while participants listened to natural continuous speech. While synthetic broad-band stimuli did not yield sustained activation of the STG, spectrotemporal receptive fields could be reconstructed from vigorous responses to speech stimuli. We find that the human STG displays a robust anterior-posterior spatial distribution of spectrotemporal tuning in which the posterior STG is tuned for temporally fast varying speech sounds that have relatively constant energy across the frequency axis (low spectral modulation) while the anterior STG is tuned for temporally slow varying speech sounds that have a high degree of spectral variation across the frequency axis (high spectral modulation). This work illustrates organization of spectrotemporal processing in the human STG, and illuminates processing of ethologically relevant speech signals in a region of the brain specialized for speech perception. SIGNIFICANCE STATEMENT: Considerable evidence has implicated the human superior temporal gyrus (STG) in speech processing. However, the gross organization of spectrotemporal processing of speech within the STG is not well characterized. Here we use natural speech stimuli and advanced receptive field characterization methods to show that spectrotemporal features within speech are well organized along the posterior-to-anterior axis of the human STG. These findings demonstrate robust functional organization based on spectrotemporal modulation content, and illustrate that much of the encoded information in the STG represents the physical acoustic properties of speech stimuli.


Assuntos
Percepção da Fala/fisiologia , Lobo Temporal/fisiologia , Estimulação Acústica , Adulto , Algoritmos , Mapeamento Encefálico , Metabolismo Energético/fisiologia , Potenciais Evocados/fisiologia , Feminino , Humanos , Masculino , Fonética
13.
J Neurophysiol ; 117(3): 910-918, 2017 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-27927787

RESUMO

Mammalian neocortical circuits are functionally organized such that the selectivity of individual neurons systematically shifts across the cortical surface, forming a continuous map. Maps of the sensory space exist in cortex, such as retinotopic maps in the visual system or tonotopic maps in the auditory system, but other functional response properties also may be similarly organized. For example, many carnivores and primates possess a map for orientation selectivity in primary visual cortex (V1), whereas mice, rabbits, and the gray squirrel lack orientation maps. In this report we show that a carnivorous rodent with predatory behaviors, the grasshopper mouse (Onychomys arenicola), lacks a canonical columnar organization of orientation preference in V1; however, neighboring neurons within 50 µm exhibit related tuning preference. Using a combination of two-photon microscopy and extracellular electrophysiology, we demonstrate that the functional organization of visual cortical neurons in the grasshopper mouse is largely the same as in the C57/BL6 laboratory mouse. We also find similarity in the selectivity for stimulus orientation, direction, and spatial frequency. Our results suggest that the properties of V1 neurons across rodent species are largely conserved.NEW & NOTEWORTHY Carnivores and primates possess a map for orientation selectivity in primary visual cortex (V1), whereas rodents and lagomorphs lack this organization. We examine, for the first time, V1 of a wild carnivorous rodent with predatory behaviors, the grasshopper mouse (Onychomys arenicola). We demonstrate the cellular organization of V1 in the grasshopper mouse is largely the same as the C57/BL6 laboratory mouse, suggesting that V1 neuron properties across rodent species are largely conserved.


Assuntos
Neurônios/fisiologia , Comportamento Predatório/fisiologia , Córtex Visual/fisiologia , Percepção Visual/fisiologia , Animais , Camundongos , Camundongos Endogâmicos C57BL , Estimulação Luminosa , Especificidade da Espécie , Vias Visuais/fisiologia
14.
Hum Brain Mapp ; 38(12): 6118-6132, 2017 12.
Artigo em Inglês | MEDLINE | ID: mdl-28921724

RESUMO

The primary motor cortex (M1) presents a somatotopic organization of body parts, but with overlap between muscle/movement representations. This distinct but overlapping M1 organization is believed to be important for individuated control and movement coordination, respectively. Discrete peaks of greater excitability observed within M1 might underpin organization of cortical motor control. This study aimed to examine interactions between M1 representations of synergist and antagonist forearm muscles, compare regions of greater excitability during different functional tasks, and compare characteristics of M1 representation recorded using surface and fine-wire (fw ) electrodes. Transcranial magnetic stimulation (TMS) was applied over M1 for mapping the representation of 4 forearm muscles (extensor carpi radialis brevis [ECRB], extensor digitorum communis, flexor carpi radialis, and flexor digitorum superficialis) during three tasks: rest, grip, and wrist extension in 14 participants. There are three main findings. First, discrete areas of peak excitability within the M1 representation of ECRBfw were identified during grip and wrist extension suggesting that different M1 areas are involved in different motor functions. Second, M1 representations of synergist muscles presented with greater overlap of M1 representations than muscles with mainly antagonist actions, which suggests a role in muscle coordination. Third, as larger normalized map volume and overlap were observed using surface than fine-wire electrodes, data suggest that cross-talk from adjacent muscles compromised interpretation of recordings made with surface electrodes in response to TMS. These results provide a novel understanding of the spatial organization of M1 with evidence of "functional somatotopy." This has important implications for cortical control of movement. Hum Brain Mapp 38:6118-6132, 2017. © 2017 Wiley Periodicals, Inc.


Assuntos
Antebraço/fisiologia , Força da Mão/fisiologia , Córtex Motor/fisiologia , Movimento/fisiologia , Músculo Esquelético/fisiologia , Mapeamento Encefálico/métodos , Eletromiografia/métodos , Potencial Evocado Motor , Feminino , Humanos , Masculino , Descanso , Estimulação Magnética Transcraniana , Adulto Jovem
15.
Cereb Cortex ; 26(1): 211-24, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-25183885

RESUMO

While functional connectivity in the human cortex has been increasingly studied, its relationship to cortical representation of sensory features has not been documented as much. We used functional magnetic resonance imaging to demonstrate that voxel-by-voxel intrinsic functional connectivity (FC) is selective to frequency preference of voxels in the human auditory cortex. Thus, FC was significantly higher for voxels with similar frequency tuning than for voxels with dissimilar tuning functions. Frequency-selective FC, measured via the correlation of residual hemodynamic activity, was not explained by generic FC that is dependent on spatial distance over the cortex. This pattern remained even when FC was computed using residual activity taken from resting epochs. Further analysis showed that voxels in the core fields in the right hemisphere have a higher frequency selectivity in within-area FC than their counterpart in the left hemisphere, or than in the noncore-fields in the same hemisphere. Frequency-selective FC is consistent with previous findings of topographically organized FC in the human visual and motor cortices. The high degree of frequency selectivity in the right core area is in line with findings and theoretical proposals regarding the asymmetry of human auditory cortex for spectral processing.


Assuntos
Córtex Auditivo/fisiologia , Mapeamento Encefálico , Córtex Motor/fisiologia , Rede Nervosa/fisiologia , Vias Neurais/fisiologia , Adulto , Mapeamento Encefálico/métodos , Feminino , Humanos , Processamento de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Masculino , Descanso/fisiologia
16.
J Neurosci ; 35(17): 6952-68, 2015 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-25926470

RESUMO

Binocular disparity is a powerful depth cue for object perception. The computations for object vision culminate in inferior temporal cortex (IT), but the functional organization for disparity in IT is unknown. Here we addressed this question by measuring fMRI responses in alert monkeys to stimuli that appeared in front of (near), behind (far), or at the fixation plane. We discovered three regions that showed preferential responses for near and far stimuli, relative to zero-disparity stimuli at the fixation plane. These "near/far" disparity-biased regions were located within dorsal IT, as predicted by microelectrode studies, and on the posterior inferotemporal gyrus. In a second analysis, we instead compared responses to near stimuli with responses to far stimuli and discovered a separate network of "near" disparity-biased regions that extended along the crest of the superior temporal sulcus. We also measured in the same animals fMRI responses to faces, scenes, color, and checkerboard annuli at different visual field eccentricities. Disparity-biased regions defined in either analysis did not show a color bias, suggesting that disparity and color contribute to different computations within IT. Scene-biased regions responded preferentially to near and far stimuli (compared with stimuli without disparity) and had a peripheral visual field bias, whereas face patches had a marked near bias and a central visual field bias. These results support the idea that IT is organized by a coarse eccentricity map, and show that disparity likely contributes to computations associated with both central (face processing) and peripheral (scene processing) visual field biases, but likely does not contribute much to computations within IT that are implicated in processing color.


Assuntos
Mapeamento Encefálico , Percepção de Cores/fisiologia , Face , Reconhecimento Visual de Modelos/fisiologia , Lobo Temporal/fisiologia , Campos Visuais/fisiologia , Animais , Viés , Percepção de Profundidade , Processamento de Imagem Assistida por Computador , Macaca mulatta , Imageamento por Ressonância Magnética , Masculino , Oxigênio/sangue , Estimulação Luminosa , Lobo Temporal/irrigação sanguínea , Disparidade Visual , Vias Visuais/irrigação sanguínea , Vias Visuais/fisiologia
17.
J Neurosci ; 35(14): 5589-605, 2015 Apr 08.
Artigo em Inglês | MEDLINE | ID: mdl-25855175

RESUMO

Vocal communication depends on the coordinated activity of sensorimotor neurons important to vocal perception and production. How vocalizations are represented by spatiotemporal activity patterns in these neuronal populations remains poorly understood. Here we combined intracellular recordings and two-photon calcium imaging in anesthetized adult zebra finches (Taeniopygia guttata) to examine how learned birdsong and its component syllables are represented in identified projection neurons (PNs) within HVC, a sensorimotor region important for song perception and production. These experiments show that neighboring HVC PNs can respond at markedly different times to song playback and that different syllables activate spatially intermingled PNs within a local (~100 µm) region of HVC. Moreover, noise correlations were stronger between PNs that responded most strongly to the same syllable and were spatially graded within and between classes of PNs. These findings support a model in which syllabic and temporal features of song are represented by spatially intermingled PNs functionally organized into cell- and syllable-type networks within local spatial scales in HVC.


Assuntos
Vias Auditivas/fisiologia , Neurônios/fisiologia , Reconhecimento Fisiológico de Modelo/fisiologia , Córtex Sensório-Motor/citologia , Córtex Sensório-Motor/fisiologia , Vocalização Animal/fisiologia , Estimulação Acústica , Potenciais de Ação/fisiologia , Animais , Cálcio/metabolismo , Estimulação Elétrica , Tentilhões , Técnicas In Vitro , Masculino , Música , Rede Nervosa/fisiologia , Compostos Orgânicos/metabolismo , Técnicas de Patch-Clamp , Telencéfalo/lesões , Telencéfalo/fisiologia , Fatores de Tempo
18.
Cereb Cortex ; 25(4): 959-71, 2015 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24122139

RESUMO

Over 40 years ago, Hubel and Wiesel gave a preliminary report of the first account of cells in monkey cerebral cortex selective for binocular disparity. The cells were located outside of V-1 within a region referred to then as "area 18." A full-length manuscript never followed, because the demarcation of the visual areas within this region had not been fully worked out. Here, we provide a full description of the physiological experiments and identify the locations of the recorded neurons using a contemporary atlas generated by functional magnetic resonance imaging; we also perform an independent analysis of the location of the neurons relative to an anatomical landmark (the base of the lunate sulcus) that is often coincident with the border between V-2 and V-3. Disparity-tuned cells resided not only in V-2, the area now synonymous with area 18, but also in V-3 and probably within V-3A. The recordings showed that the disparity-tuned cells were biased for near disparities, tended to prefer vertical orientations, clustered by disparity preference, and often required stimulation of both eyes to elicit responses, features strongly suggesting a role in stereoscopic depth perception.


Assuntos
Neurônios/fisiologia , Disparidade Visual/fisiologia , Córtex Visual/fisiologia , Potenciais de Ação , Animais , Atlas como Assunto , Macaca , Masculino , Microeletrodos , Estimulação Luminosa , Visão Binocular/fisiologia
19.
J Neurophysiol ; 112(4): 981-98, 2014 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-25128560

RESUMO

The central auditory system has traditionally been divided into lemniscal and nonlemniscal pathways leading from the midbrain through the thalamus to the cortex. This view has served as an organizing principle for studying, modeling, and understanding the encoding of sound within the brain. However, there is evidence that the lemniscal pathway could be further divided into at least two subpathways, each potentially coding for sound in different ways. We investigated whether such an interpretation is supported by the spatial distribution of response features in the central nucleus of the inferior colliculus (ICC), the part of the auditory midbrain assigned to the lemniscal pathway. We recorded responses to pure tone stimuli in the ICC of ketamine-xylazine-anesthetized guinea pigs and used three-dimensional brain reconstruction techniques to map the location of the recording sites. Compared with neurons in caudal-and-medial regions within an isofrequency lamina of the ICC, neurons in rostral-and-lateral regions responded with shorter first-spike latencies with less spiking jitter, shorter durations of spiking responses, a higher proportion of spikes occurring near the onset of the stimulus, lower thresholds, and larger local field potentials with shorter latencies. Further analysis revealed two distinct clusters of response features located in either the caudal-and-medial or the rostral-and-lateral parts of the isofrequency laminae of the ICC. Thus we report substantial differences in coding properties in two regions of the ICC that are consistent with the hypothesis that the lemniscal pathway is made up of at least two distinct subpathways from the midbrain up to the cortex.


Assuntos
Vias Auditivas/fisiologia , Potenciais Evocados Auditivos do Tronco Encefálico , Colículos Inferiores/fisiologia , Tegmento Pontino/fisiologia , Animais , Vias Auditivas/citologia , Feminino , Cobaias , Colículos Inferiores/citologia , Masculino , Neurônios/fisiologia , Tegmento Pontino/citologia , Tempo de Reação
20.
Res Sq ; 2024 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-38260553

RESUMO

Current models of scene processing in the human brain include three scene-selective areas: the Parahippocampal Place Area (or the temporal place areas; PPA/TPA), the restrosplenial cortex (or the medial place area; RSC/MPA) and the transverse occipital sulcus (or the occipital place area; TOS/OPA). Here, we challenged this model by showing that at least one other scene-selective site can also be detected within the human posterior intraparietal gyrus. Despite the smaller size of this site compared to the other scene-selective areas, the posterior intraparietal gyrus scene-selective (PIGS) site was detected consistently in a large pool of subjects (n=59; 33 females). The reproducibility of this finding was tested based on multiple criteria, including comparing the results across sessions, utilizing different scanners (3T and 7T) and stimulus sets. Furthermore, we found that this site (but not the other three scene-selective areas) is significantly sensitive to ego-motion in scenes, thus distinguishing the role of PIGS in scene perception relative to other scene-selective areas. These results highlight the importance of including finer scale scene-selective sites in models of scene processing - a crucial step toward a more comprehensive understanding of how scenes are encoded under dynamic conditions.

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