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1.
Cereb Cortex ; 30(4): 2658-2672, 2020 04 14.
Artigo em Inglês | MEDLINE | ID: mdl-31828299

RESUMO

Visual motion processing is a well-established model system for studying neural population codes in primates. The common marmoset, a small new world primate, offers unparalleled opportunities to probe these population codes in key motion processing areas, such as cortical areas MT and MST, because these areas are accessible for imaging and recording at the cortical surface. However, little is currently known about the perceptual abilities of the marmoset. Here, we introduce a paradigm for studying motion perception in the marmoset and compare their psychophysical performance with human observers. We trained two marmosets to perform a motion estimation task in which they provided an analog report of their perceived direction of motion with an eye movement to a ring that surrounded the motion stimulus. Marmosets and humans exhibited similar trade-offs in speed versus accuracy: errors were larger and reaction times were longer as the strength of the motion signal was reduced. Reverse correlation on the temporal fluctuations in motion direction revealed that both species exhibited short integration windows; however, marmosets had substantially less nondecision time than humans. Our results provide the first quantification of motion perception in the marmoset and demonstrate several advantages to using analog estimation tasks.

2.
J Vis ; 19(11): 12, 2019 09 03.
Artigo em Inglês | MEDLINE | ID: mdl-31557762

RESUMO

Saccadic eye movements sample the visual world and ensure high acuity across the visual field. To compensate for delays in processing, saccades to moving targets require predictions: The eyes must intercept the target's future position to then pursue its direction of motion. Although prediction is crucial to voluntary pursuit, it is unclear whether it is an obligatory feature of saccade planning. Saccade planning involves an involuntary enhanced processing of the target, called presaccadic attention. Does this presaccadic attention recruit smooth eye movements automatically? To test this, we had human participants perform a saccade to one of four apertures, which were static, but each contained a random dot field with motion tangential to the required saccade. In this task, saccades were deviated along the direction of target motion, and the eyes exhibited a following response upon saccade landing. This postsaccadic following response (PFR) increased with spatial uncertainty of the target position and persisted even when we removed the motion stimulus in midflight of the saccade, confirming that it relied on presaccadic information. Motion from 50-100 ms prior to the saccade had the strongest influence on PFR, consistent with the time course of perceptual enhancements reported in presaccadic attention. Finally, the PFR magnitude related linearly to the logarithm of stimulus velocity and generally had low gain, similar to involuntary ocular following movements commonly observed after sudden motion onsets. These results suggest that presaccadic attention selects motion features of targets predictively, presumably to ensure successful immediate tracking of saccade targets in motion.


Assuntos
Atenção/fisiologia , Movimentos Sacádicos/fisiologia , Adolescente , Adulto , Antecipação Psicológica/fisiologia , Feminino , Humanos , Masculino , Movimento (Física) , Estimulação Luminosa , Tempo de Reação/fisiologia , Percepção Espacial/fisiologia , Incerteza , Visão Ocular/fisiologia , Campos Visuais/fisiologia , Adulto Jovem
3.
Dev Neurobiol ; 77(3): 300-313, 2017 03.
Artigo em Inglês | MEDLINE | ID: mdl-27804251

RESUMO

The common marmoset has attracted increasing interest as a model for visual neuroscience. A measurement of fundamental importance to ensure the validity of visual studies is spatial acuity. The marmoset has excellent acuity that has been reported at the fovea to be nearly half that of the human (Ordy and Samorajski []: Vision Res 8:1205-1225), a value that is consistent with them having similar photoreceptor densities combined with their smaller eye size (Troilo et al. []: Vision Res 33:1301-1310). Of interest, the marmoset exhibits a higher proportion of cones than rods in peripheral vision than human or macaque, which in principle could endow them with better peripheral acuity depending on how those signals are pooled in subsequent processing. Here, we introduce a simple behavioral paradigm to measure acuity and then test how acuity in the marmoset scales with eccentricity. We trained subjects to fixate a central point and detect a peripheral Gabor by making a saccade to its location. First, we found that accurate assessment of acuity required correction for myopia in all adult subjects. This is an important point because marmosets raised in laboratory conditions often have mild to severe myopia (Graham and Judge []: Vision Res 39:177-187), a finding that we confirm, and that would limit their utility for studies of vision if uncorrected. With corrected vision, we found that their acuity scales with eccentricity similar to that of humans and macaques, having roughly half the value of the human and with no clear departure for higher acuity in the periphery. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 300-313, 2017.


Assuntos
Callithrix/fisiologia , Movimentos Oculares/fisiologia , Modelos Animais , Miopia/fisiopatologia , Reconhecimento Visual de Modelos/fisiologia , Psicofísica/métodos , Acuidade Visual/fisiologia , Animais , Comportamento Animal
4.
Neuron ; 91(4): 920-930, 2016 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-27499085

RESUMO

To deepen our understanding of object recognition, it is critical to understand the nature of transformations that occur in intermediate stages of processing in the ventral visual pathway, such as area V4. Neurons in V4 are selective to local features of global shape, such as extended contours. Previously, we found that V4 neurons selective for curved elements exhibit a high degree of spatial variation in their preference. If spatial variation in curvature selectivity was also marked by distinct temporal response patterns at different spatial locations, then it might be possible to untangle this information in subsequent processing based on temporal responses. Indeed, we find that V4 neurons whose receptive fields exhibit intricate selectivity also show variation in their temporal responses across locations. A computational model that decodes stimulus identity based on population responses benefits from using this temporal information, suggesting that it could provide a multiplexed code for spatio-temporal features.


Assuntos
Percepção de Forma/fisiologia , Neurônios/fisiologia , Córtex Visual/citologia , Córtex Visual/fisiologia , Animais , Macaca mulatta , Modelos Neurológicos , Estimulação Luminosa , Fatores de Tempo
5.
J Neurophysiol ; 116(3): 1286-94, 2016 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-27334951

RESUMO

Optogenetics has revolutionized the study of functional neuronal circuitry (Boyden ES, Zhang F, Bamberg E, Nagel G, Deisseroth K. Nat Neurosci 8: 1263-1268, 2005; Deisseroth K. Nat Methods 8: 26-29, 2011). Although these techniques have been most successfully implemented in rodent models, they have the potential to be similarly impactful in studies of nonhuman primate brains. Common marmosets (Callithrix jacchus) have recently emerged as a candidate primate model for gene editing, providing a potentially powerful model for studies of neural circuitry and disease in primates. The application of viral transduction methods in marmosets for identifying and manipulating neuronal circuitry is a crucial step in developing this species for neuroscience research. In the present study we developed a novel, chronic method to successfully induce rapid photostimulation in individual cortical neurons transduced by adeno-associated virus to express channelrhodopsin (ChR2) in awake marmosets. We found that large proportions of neurons could be effectively photoactivated following viral transduction and that this procedure could be repeated for several months. These data suggest that techniques for viral transduction and optical manipulation of neuronal populations are suitable for marmosets and can be combined with existing behavioral preparations in the species to elucidate the functional neural circuitry underlying perceptual and cognitive processes.


Assuntos
Encéfalo/fisiologia , Callithrix/fisiologia , Neurônios/fisiologia , Optogenética , Potenciais de Ação , Animais , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Dependovirus/genética , Feminino , Vetores Genéticos , Proteínas Luminescentes/genética , Proteínas Luminescentes/metabolismo , Microeletrodos , Modelos Animais , Vias Neurais/fisiologia , Estimulação Luminosa , Rodopsina/genética , Rodopsina/metabolismo , Sorogrupo , Vigília
6.
Comp Med ; 66(3): 254-8, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27298252

RESUMO

A 5-y-old multiparous female common marmoset (Callithrix jacchus) presented with acute weight loss of approximately 25% over a 1-wk period. An abdominal mass was apparent on physical examination, and radiographs suggested peritoneal effusion. Exploratory laparotomy revealed hemoperitoneum and an enlarged, gray, hemorrhaging uterus; ovariohysterectomy was performed, and the marmoset recovered. Histologic evaluation of the ovaries and uterus revealed uterine rupture, with invasion of placental villi lined by trophoblasts through the myometrium to the serosal layer. Primary uterine rupture is a rare but serious obstetric event in humans and has been reported only rarely in NHP. This report is the first description of primary uterine rupture during early pregnancy in a common marmoset.


Assuntos
Doenças dos Macacos/diagnóstico por imagem , Ruptura Uterina/veterinária , Animais , Callithrix , Feminino , Doenças dos Macacos/patologia , Ruptura Uterina/diagnóstico por imagem , Ruptura Uterina/patologia
7.
Neuron ; 90(2): 219-33, 2016 04 20.
Artigo em Inglês | MEDLINE | ID: mdl-27100195

RESUMO

The common marmoset (Callithrix jacchus) has garnered interest recently as a powerful model for the future of neuroscience research. Much of this excitement has centered on the species' reproductive biology and compatibility with gene editing techniques, which together have provided a path for transgenic marmosets to contribute to the study of disease as well as basic brain mechanisms. In step with technical advances is the need to establish experimental paradigms that optimally tap into the marmosets' behavioral and cognitive capacities. While conditioned task performance of a marmoset can compare unfavorably with rhesus monkey performance on conventional testing paradigms, marmosets' social behavior and cognition are more similar to that of humans. For example, marmosets are among only a handful of primates that, like humans, routinely pair bond and care cooperatively for their young. They are also notably pro-social and exhibit social cognitive abilities, such as imitation, that are rare outside of the Apes. In this Primer, we describe key facets of marmoset natural social behavior and demonstrate that emerging behavioral paradigms are well suited to isolate components of marmoset cognition that are highly relevant to humans. These approaches generally embrace natural behavior, which has been rare in conventional primate testing, and thus allow for a new consideration of neural mechanisms underlying primate social cognition and signaling. We anticipate that through parallel technical and paradigmatic advances, marmosets will become an essential model of human social behavior, including its dysfunction in neuropsychiatric disorders.


Assuntos
Callithrix/psicologia , Modelos Animais , Comportamento Social , Animais , Animais Geneticamente Modificados/psicologia , Encéfalo/fisiologia , Callithrix/genética , Cognição , Modelos Animais de Doenças , Movimentos Oculares/fisiologia , Haplorrinos/psicologia , Humanos , Roedores , Transtornos do Comportamento Social/genética , Transtornos do Comportamento Social/psicologia , Vocalização Animal/fisiologia
8.
Neuron ; 86(3): 617-31, 2015 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-25950631

RESUMO

One of the great strengths of the mouse model is the wide array of genetic tools that have been developed. Striking examples include methods for directed modification of the genome, and for regulated expression or inactivation of genes. Within neuroscience, it is now routine to express reporter genes, neuronal activity indicators, and opsins in specific neuronal types in the mouse. However, there are considerable anatomical, physiological, cognitive, and behavioral differences between the mouse and the human that, in some areas of inquiry, limit the degree to which insights derived from the mouse can be applied to understanding human neurobiology. Several recent advances have now brought into reach the goal of applying these tools to understanding the primate brain. Here we describe these advances, consider their potential to advance our understanding of the human brain and brain disorders, discuss bioethical considerations, and describe what will be needed to move forward.


Assuntos
Encéfalo/fisiologia , Genes , Primatas/genética , Animais , Evolução Biológica , Humanos , Camundongos , Modelos Biológicos
9.
J Neurophysiol ; 113(10): 3954-60, 2015 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-25867740

RESUMO

Smooth pursuit eye movements stabilize slow-moving objects on the retina by matching eye velocity with target velocity. Two critical components are required to generate smooth pursuit: first, because it is a voluntary eye movement, the subject must select a target to pursue to engage the tracking system; and second, generating smooth pursuit requires a moving stimulus. We examined whether this behavior also exists in the common marmoset, a New World primate that is increasingly attracting attention as a genetic model for mental disease and systems neuroscience. We measured smooth pursuit in two marmosets, previously trained to perform fixation tasks, using the standard Rashbass step-ramp pursuit paradigm. We first measured the aspects of visual motion that drive pursuit eye movements. Smooth eye movements were in the same direction as target motion, indicating that pursuit was driven by target movement rather than by displacement. Both the open-loop acceleration and closed-loop eye velocity exhibited a linear relationship with target velocity for slow-moving targets, but this relationship declined for higher speeds. We next examined whether marmoset pursuit eye movements depend on an active engagement of the pursuit system by measuring smooth eye movements evoked by small perturbations of motion from fixation or during pursuit. Pursuit eye movements were much larger during pursuit than from fixation, indicating that pursuit is actively gated. Several practical advantages of the marmoset brain, including the accessibility of the middle temporal (MT) area and frontal eye fields at the cortical surface, merit its utilization for studying pursuit movements.


Assuntos
Percepção de Movimento/fisiologia , Movimento (Física) , Acompanhamento Ocular Uniforme/fisiologia , Retina/fisiologia , Aceleração , Animais , Callithrix , Estimulação Luminosa , Campos Visuais/fisiologia
10.
Proc Biol Sci ; 282(1807): 20150069, 2015 May 22.
Artigo em Inglês | MEDLINE | ID: mdl-25904663

RESUMO

Conversational turn-taking is an integral part of language development, as it reflects a confluence of social factors that mitigate communication. Humans coordinate the timing of speech based on the behaviour of another speaker, a behaviour that is learned during infancy. While adults in several primate species engage in vocal turn-taking, the degree to which similar learning processes underlie its development in these non-human species or are unique to language is not clear. We recorded the natural vocal interactions of common marmosets (Callithrix jacchus) occurring with both their sibling twins and parents over the first year of life and observed at least two parallels with language development. First, marmoset turn-taking is a learned vocal behaviour. Second, marmoset parents potentially played a direct role in guiding the development of turn-taking by providing feedback to their offspring when errors occurred during vocal interactions similarly to what has been observed in humans. Though species-differences are also evident, these findings suggest that similar learning mechanisms may be implemented in the ontogeny of vocal turn-taking across our Order, a finding that has important implications for our understanding of language evolution.


Assuntos
Comunicação Animal , Callithrix/fisiologia , Aprendizagem , Vocalização Animal , Animais , Callithrix/crescimento & desenvolvimento , Comportamento Cooperativo , Feminino , Masculino
11.
Neurosci Res ; 93: 20-46, 2015 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-25683292

RESUMO

The common marmoset (Callithrix jacchus) has been valuable as a primate model in biomedical research. Interest in this species has grown recently, in part due to the successful demonstration of transgenic marmosets. Here we examine the prospects of the marmoset model for visual neuroscience research, adopting a comparative framework to place the marmoset within a broader evolutionary context. The marmoset's small brain bears most of the organizational features of other primates, and its smooth surface offers practical advantages over the macaque for areal mapping, laminar electrode penetration, and two-photon and optical imaging. Behaviorally, marmosets are more limited at performing regimented psychophysical tasks, but do readily accept the head restraint that is necessary for accurate eye tracking and neurophysiology, and can perform simple discriminations. Their natural gaze behavior closely resembles that of other primates, with a tendency to focus on objects of social interest including faces. Their immaturity at birth and routine twinning also makes them ideal for the study of postnatal visual development. These experimental factors, together with the theoretical advantages inherent in comparing anatomy, physiology, and behavior across related species, make the marmoset an excellent model for visual neuroscience.


Assuntos
Encéfalo/fisiologia , Callithrix/fisiologia , Modelos Animais , Visão Ocular/fisiologia , Percepção Visual , Animais , Evolução Biológica , Percepção de Cores , Visão de Cores/fisiologia , Comportamento Exploratório , Macaca/fisiologia , Comportamento Social , Visão Binocular
12.
Comp Med ; 64(4): 300-8, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-25427343

RESUMO

Macaques are the most common animal model for studies in vision research, and due to their high value as research subjects, often continue to participate in studies well into old age. As is true in humans, visual acuity in macaques is susceptible to refractive errors. Here we report a case study in which an aged macaque demonstrated clear impairment in visual acuity according to performance on a demanding behavioral task. Refraction demonstrated bilateral myopia that significantly affected behavioral and visual tasks. Using corrective lenses, we were able to restore visual acuity. After correction of myopia, the macaque's performance on behavioral tasks was comparable to that of a healthy control. We screened 20 other male macaques to assess the incidence of refractive errors and ocular pathologies in a larger population. Hyperopia was the most frequent ametropia but was mild in all cases. A second macaque had mild myopia and astigmatism in one eye. There were no other pathologies observed on ocular examination. We developed a simple behavioral task that visual research laboratories could use to test visual acuity in macaques. The test was reliable and easily learned by the animals in 1 d. This case study stresses the importance of screening macaques involved in visual science for refractive errors and ocular pathologies to ensure the quality of research; we also provide simple methodology for screening visual acuity in these animals.


Assuntos
Animais de Laboratório , Astigmatismo/veterinária , Óculos/veterinária , Macaca mulatta , Doenças dos Macacos/terapia , Miopia/veterinária , Visão Ocular , Fatores Etários , Animais , Astigmatismo/diagnóstico , Astigmatismo/fisiopatologia , Astigmatismo/psicologia , Astigmatismo/terapia , Comportamento Animal , Masculino , Doenças dos Macacos/diagnóstico , Doenças dos Macacos/fisiopatologia , Doenças dos Macacos/psicologia , Miopia/diagnóstico , Miopia/fisiopatologia , Miopia/psicologia , Miopia/terapia , Valor Preditivo dos Testes , Refração Ocular , Reprodutibilidade dos Testes , Testes Visuais/veterinária , Acuidade Visual
13.
J Neurosci ; 34(4): 1183-94, 2014 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-24453311

RESUMO

The common marmoset (Callithrix jacchus), a small-bodied New World primate, offers several advantages to complement vision research in larger primates. Studies in the anesthetized marmoset have detailed the anatomy and physiology of their visual system (Rosa et al., 2009) while studies of auditory and vocal processing have established their utility for awake and behaving neurophysiological investigations (Lu et al., 2001a,b; Eliades and Wang, 2008a,b; Osmanski and Wang, 2011; Remington et al., 2012). However, a critical unknown is whether marmosets can perform visual tasks under head restraint. This has been essential for studies in macaques, enabling both accurate eye tracking and head stabilization for neurophysiology. In one set of experiments we compared the free viewing behavior of head-fixed marmosets to that of macaques, and found that their saccadic behavior is comparable across a number of saccade metrics and that saccades target similar regions of interest including faces. In a second set of experiments we applied behavioral conditioning techniques to determine whether the marmoset could control fixation for liquid reward. Two marmosets could fixate a central point and ignore peripheral flashing stimuli, as needed for receptive field mapping. Both marmosets also performed an orientation discrimination task, exhibiting a saturating psychometric function with reliable performance and shorter reaction times for easier discriminations. These data suggest that the marmoset is a viable model for studies of active vision and its underlying neural mechanisms.


Assuntos
Callithrix , Modelos Animais , Neurofisiologia/métodos , Neurociências/métodos , Visão Ocular/fisiologia , Percepção Visual/fisiologia , Animais , Condicionamento Operante , Movimentos Sacádicos/fisiologia
14.
Nat Neurosci ; 16(8): 1125-31, 2013 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-23852114

RESUMO

Attention improves the encoding of visual stimuli. One mechanism that is implicated in facilitating sensory encoding is the firing of action potentials in bursts. We tested the hypothesis that when spatial attention is directed to a stimulus, this causes an increase in burst firing to the attended stimulus. To the contrary, we found an attention-dependent reduction in 'burstiness' among putative pyramidal neurons in macaque area V4. We accounted for this using a conductance-based Hodgkin-Huxley style model in which attentional modulation stems from scaling excitation and inhibition. The model exhibited attention-dependent increases in firing rate and made the surprising and correct prediction that when attention is directed into a neuron's receptive field, this reduces action-potential height. The model thus provided a unified explanation for three distinct forms of attentional modulation, two of them previously undescribed, and implicates scaling of the responses of excitatory and inhibitory input populations in mediating attention.


Assuntos
Potenciais de Ação/fisiologia , Atenção/fisiologia , Interneurônios/fisiologia , Modelos Neurológicos , Células Piramidais/fisiologia , Córtex Visual/fisiologia , Animais , Sinais (Psicologia) , Transporte de Íons , Macaca , Masculino , Técnicas de Patch-Clamp , Estimulação Luminosa , Canais de Potássio de Abertura Dependente da Tensão da Membrana/fisiologia , Desempenho Psicomotor/fisiologia , Córtex Visual/citologia
15.
Neuron ; 78(6): 1102-15, 2013 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-23791199

RESUMO

Previous studies have shown that neurons in area V4 are involved in the processing of shapes of intermediate complexity and are sensitive to curvature. These studies also suggest that curvature-tuned neurons are position invariant. We sought to examine the mechanisms that endow V4 neurons with these properties. Consistent with previous studies, we found that response rank order to the most- and least-preferred stimuli was preserved throughout the receptive field. However, a fine-grained analysis of shape tuning revealed a surprising result: V4 neurons tuned to highly curved shapes exhibit very limited translation invariance. At a fine spatial scale, these neurons exhibit local variation in orientation. In contrast, neurons that prefer straight contours exhibit spatially invariant orientation-tuning and homogenous fine-scale orientation maps. Both of these patterns are consistent with a simple orientation-pooling model, with tuning for straight or curved shapes resulting, respectively, from pooling of homogenous or heterogeneous orientation signals inherited from early visual areas.


Assuntos
Percepção de Forma/fisiologia , Reconhecimento Visual de Modelos/fisiologia , Estimulação Luminosa/métodos , Córtex Visual/citologia , Córtex Visual/fisiologia , Animais , Macaca mulatta
16.
J Neurosci ; 32(45): 16040-50, 2012 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-23136440

RESUMO

Many previous studies have demonstrated that changes in selective attention can alter the response magnitude of visual cortical neurons, but there has been little evidence for attention affecting response latency. Small latency differences, though hard to detect, can potentially be of functional importance, and may also give insight into the mechanisms of neuronal computation. We therefore reexamined the effect of attention on the response latency of both single units and the local field potential (LFP) in primate visual cortical area V4. We find that attention does produce small (1-2 ms) but significant reductions in the latency of both the spiking and LFP responses. Though attention, like contrast elevation, reduces response latencies, we find that the two have different effects on the magnitude of the LFP. Contrast elevations increase and attention decreases the magnitude of the initial deflection of the stimulus-evoked LFP. Both contrast elevation and attention increase the magnitude of the spiking response. We speculate that latencies may be reduced at higher contrast because stronger stimulus inputs drive neurons more rapidly to spiking threshold, while attention may reduce latencies by placing neurons in a more depolarized state closer to threshold before stimulus onset.


Assuntos
Potenciais de Ação/fisiologia , Atenção/fisiologia , Neurônios/fisiologia , Tempo de Reação/fisiologia , Córtex Visual/fisiologia , Animais , Potenciais Evocados Visuais/fisiologia , Macaca mulatta , Masculino , Estimulação Luminosa
17.
J Neurosci ; 31(30): 10983-92, 2011 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-21795547

RESUMO

One of the most well established forms of attentional modulation is an increase in firing rate when attention is directed into the receptive field of a neuron. The degree of rate modulation, however, can vary considerably across individual neurons, especially among broad spiking neurons (putative pyramids). We asked whether this heterogeneity might be correlated with a neuronal response property that is used in intracellular recording studies to distinguish among distinct neuronal classes: the burstiness of the neuronal spike train. We first characterized the burst spiking behavior of visual area V4 neurons and found that this varies considerably across the population, but we did not find evidence for distinct classes of burst behavior. Burstiness did, however, vary more widely across the class of neurons that shows the greatest heterogeneity in attentional modulation, and within that class, burstiness helped account for differences in attentional modulation. Among these broad spiking neurons, rate modulation was primarily restricted to bursty neurons, which as a group showed a highly significant increase in firing rate with attention. Furthermore, every bursty broad spiking neuron whose firing rate was significantly modulated by attention exhibited an increase in firing rate. In contrast, non-bursty broad spiking neurons exhibited no net attentional modulation, and, although some individual neurons did show significant rate modulation, these were divided among neurons showing increases and decreases. These findings show that macaque area V4 shows a range of bursting behavior and that the heterogeneity of attentional modulation can be explained, in part, by variation in burstiness.


Assuntos
Potenciais de Ação/fisiologia , Atenção/fisiologia , Células Piramidais/fisiologia , Córtex Visual/citologia , Animais , Macaca , Testes Neuropsicológicos , Estimulação Luminosa/métodos , Movimentos Sacádicos/fisiologia
18.
J Neurophysiol ; 105(3): 1258-65, 2011 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-21228306

RESUMO

Faced with an overwhelming amount of sensory information, we are able to prioritize the processing of select spatial locations and visual features. The neuronal mechanisms underlying such spatial and feature-based selection have been studied in considerable detail. More recent work shows that attention can also be allocated to objects, even spatially superimposed objects composed of dynamically changing features that must be integrated to create a coherent object representation. Much less is known about the mechanisms underlying such object-based selection. Our goal was to investigate behavioral and neuronal responses when attention was directed to one of two objects, specifically one of two superimposed transparent surfaces, in a task designed to preclude space-based and feature-based selection. We used functional magnetic resonance imaging (fMRI) to measure changes in blood oxygen level-dependent (BOLD) signals when attention was deployed to one or the other surface. We found that visual areas V1, V2, V3, V3A, and MT+ showed enhanced BOLD responses to translations of an attended relative to an unattended surface. These results reveal that visual areas as early as V1 can be modulated by attending to objects, even objects defined by dynamically changing elements. This provides definitive evidence in humans that early visual areas are involved in a seemingly high-order process. Furthermore, our results suggest that these early visual areas may participate in object-specific feature "binding," a process that seemingly must occur for an object or a surface to be the unit of attentional selection.


Assuntos
Atenção/fisiologia , Sinais (Psicologia) , Potenciais Evocados Visuais/fisiologia , Reconhecimento Visual de Modelos/fisiologia , Córtex Visual/fisiologia , Adaptação Fisiológica/fisiologia , Adulto , Feminino , Humanos , Masculino
19.
Neuron ; 63(6): 879-88, 2009 Sep 24.
Artigo em Inglês | MEDLINE | ID: mdl-19778515

RESUMO

Attention typically amplifies neuronal responses evoked by task-relevant stimuli while attenuating responses to task-irrelevant distracters. In this context, visual distracters constitute an external source of noise that is diminished to improve attended signal quality. Activity that is internal to the cortex itself, stimulus-independent ongoing correlated fluctuations in firing, might also act as task-irrelevant noise. To examine this, we recorded from area V4 of macaques performing an attention-demanding task. The firing of neurons to identically repeated stimuli was highly variable. Much of this variability originates from ongoing low-frequency (<5 Hz) fluctuations in rate correlated across the neuronal population. When attention is directed to a stimulus inside a neuron's receptive field, these correlated fluctuations in rate are reduced. This attention-dependent reduction of ongoing cortical activity improves the signal-to-noise ratio of pooled neural signals substantially more than attention-dependent increases in firing rate.


Assuntos
Potenciais de Ação/fisiologia , Atenção/fisiologia , Macaca/fisiologia , Neurônios/fisiologia , Percepção Espacial/fisiologia , Córtex Visual/citologia , Animais , Testes Neuropsicológicos , Estimulação Luminosa/métodos , Tempo de Reação , Estatística como Assunto , Fatores de Tempo , Córtex Visual/fisiologia , Campos Visuais , Vias Visuais
20.
Neuron ; 61(6): 952-63, 2009 Mar 26.
Artigo em Inglês | MEDLINE | ID: mdl-19324003

RESUMO

In natural viewing, a visual stimulus that is the target of attention is generally surrounded by many irrelevant distracters. Stimuli falling in the receptive field surround can influence the neuronal response evoked by a stimulus appearing within the classical receptive field. Such modulation by task-irrelevant distracters may degrade the target-related neuronal signal. We therefore examined whether directing attention to a target stimulus can reduce the influence of task-irrelevant distracters on neuronal response. We find that in area V4 attention to a stimulus within a neuron's receptive field filters out a large fraction of the suppression induced by distracters appearing in the surround. When attention is instead directed to the surround stimulus, suppression is increased, thereby filtering out part of the neuronal response to the irrelevant distracter positioned within the receptive field. These findings demonstrate that attention modulates the neural mechanisms that give rise to center-surround interactions.


Assuntos
Atenção/fisiologia , Sensibilidades de Contraste/fisiologia , Percepção Espacial/fisiologia , Córtex Visual/fisiologia , Campos Visuais/fisiologia , Potenciais de Ação/fisiologia , Animais , Movimentos Oculares/fisiologia , Macaca mulatta , Masculino , Neurônios/fisiologia , Estimulação Luminosa/métodos , Tempo de Reação/fisiologia , Fatores de Tempo , Córtex Visual/citologia
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