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1.
Neuroimage ; 235: 118017, 2021 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-33794355

RESUMO

Brain perturbation studies allow detailed causal inferences of behavioral and neural processes. Because the combination of brain perturbation methods and neural measurement techniques is inherently challenging, research in humans has predominantly focused on non-invasive, indirect brain perturbations, or neurological lesion studies. Non-human primates have been indispensable as a neurobiological system that is highly similar to humans while simultaneously being more experimentally tractable, allowing visualization of the functional and structural impact of systematic brain perturbation. This review considers the state of the art in non-human primate brain perturbation with a focus on approaches that can be combined with neuroimaging. We consider both non-reversible (lesions) and reversible or temporary perturbations such as electrical, pharmacological, optical, optogenetic, chemogenetic, pathway-selective, and ultrasound based interference methods. Method-specific considerations from the research and development community are offered to facilitate research in this field and support further innovations. We conclude by identifying novel avenues for further research and innovation and by highlighting the clinical translational potential of the methods.


Assuntos
Encéfalo/diagnóstico por imagem , Encéfalo/fisiologia , Neuroimagem/métodos , Animais , Humanos , Optogenética , Primatas
2.
Neuroimage ; 226: 117519, 2021 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-33227425

RESUMO

Neuroimaging non-human primates (NHPs) is a growing, yet highly specialized field of neuroscience. Resources that were primarily developed for human neuroimaging often need to be significantly adapted for use with NHPs or other animals, which has led to an abundance of custom, in-house solutions. In recent years, the global NHP neuroimaging community has made significant efforts to transform the field towards more open and collaborative practices. Here we present the PRIMatE Resource Exchange (PRIME-RE), a new collaborative online platform for NHP neuroimaging. PRIME-RE is a dynamic community-driven hub for the exchange of practical knowledge, specialized analytical tools, and open data repositories, specifically related to NHP neuroimaging. PRIME-RE caters to both researchers and developers who are either new to the field, looking to stay abreast of the latest developments, or seeking to collaboratively advance the field .


Assuntos
Acesso à Informação , Neuroimagem/métodos , Sistemas On-Line , Primatas/anatomia & histologia , Primatas/fisiologia , Animais
3.
Neuron ; 100(1): 61-74.e2, 2018 10 10.
Artigo em Inglês | MEDLINE | ID: mdl-30269990

RESUMO

Non-human primate neuroimaging is a rapidly growing area of research that promises to transform and scale translational and cross-species comparative neuroscience. Unfortunately, the technological and methodological advances of the past two decades have outpaced the accrual of data, which is particularly challenging given the relatively few centers that have the necessary facilities and capabilities. The PRIMatE Data Exchange (PRIME-DE) addresses this challenge by aggregating independently acquired non-human primate magnetic resonance imaging (MRI) datasets and openly sharing them via the International Neuroimaging Data-sharing Initiative (INDI). Here, we present the rationale, design, and procedures for the PRIME-DE consortium, as well as the initial release, consisting of 25 independent data collections aggregated across 22 sites (total = 217 non-human primates). We also outline the unique pitfalls and challenges that should be considered in the analysis of non-human primate MRI datasets, including providing automated quality assessment of the contributed datasets.


Assuntos
Encéfalo , Conjuntos de Dados como Assunto , Neuroimagem , Animais , Encéfalo/anatomia & histologia , Encéfalo/fisiologia , Conectoma/métodos , Disseminação de Informação/métodos , Imageamento por Ressonância Magnética , Primatas
4.
Trends Cogn Sci ; 22(7): 598-610, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29729902

RESUMO

Recent advances in neuroscience and technology have made it possible to record from large assemblies of neurons and to decode their activity to extract information. At the same time, available methods to stimulate the brain and influence ongoing processing are also rapidly expanding. These developments pave the way for advanced neurotechnological applications that directly read from, and write to, the human brain. While such technologies are still primarily used in restricted therapeutic contexts, this may change in the future once their performance has improved and they become more widely applicable. Here, we provide an overview of methods to interface with the brain, speculate about potential applications, and discuss important issues associated with a neurotechnologically assisted future.


Assuntos
Interfaces Cérebro-Computador , Encéfalo/fisiologia , Processos Mentais/fisiologia , Animais , Estado de Consciência/fisiologia , Humanos
5.
Sci Rep ; 7(1): 9082, 2017 08 22.
Artigo em Inglês | MEDLINE | ID: mdl-28831072

RESUMO

The richness of sensory input dictates that the brain must prioritize and select information for further processing and storage in working memory. Stimulus salience and reward expectations influence this prioritization but their relative contributions and underlying mechanisms are poorly understood. Here we investigate how the quality of working memory for multiple stimuli is determined by priority during encoding and later memory phases. Selective attention could, for instance, act as the primary gating mechanism when stimuli are still visible. Alternatively, observers might still be able to shift priorities across memories during maintenance or retrieval. To distinguish between these possibilities, we investigated how and when reward cues determine working memory accuracy and found that they were only effective during memory encoding. Previously learned, but currently non-predictive, color-reward associations had a similar influence, which gradually weakened without reinforcement. Finally, we show that bottom-up salience, manipulated through varying stimulus contrast, influences memory accuracy during encoding with a fundamentally different time-course than top-down reward cues. While reward-based effects required long stimulus presentation, the influence of contrast was strongest with brief presentations. Our results demonstrate how memory resources are distributed over memory targets and implicates selective attention as a main gating mechanism between sensory and memory systems.


Assuntos
Encéfalo/fisiologia , Memória de Curto Prazo , Recompensa , Análise de Variância , Feminino , Humanos , Masculino , Estimulação Física
6.
Sci Rep ; 7(1): 7585, 2017 08 08.
Artigo em Inglês | MEDLINE | ID: mdl-28790394

RESUMO

Faces are important visual objects for humans and other social animals. A complex network of specialized brain areas is involved in the recognition and interpretation of faces. This network needs to strike a balance between being sensitive enough to distinguish between different faces with similar features, and being tolerant of low-level visual changes so that a given face is stably perceived as a particular individual. Such stability may require feedback from higher brain regions down to the level where details are represented. Here, we describe a phenomenon in which interocular competition between face features is stabilized and eliminated when observers attend high-level face characteristics. Two different face images presented to the individual eyes do not cause the perceptual fluctuations that are typically observed in binocular rivalry. Instead, they merge into a stable percept of an intermediate face that combines features from both eyes' images. The stability of the intermediate face percept depends on the observer attending holistic face properties such as identity or gender. It disappears when observers explicitly attend facial features, suggesting a crucial role of top-down stabilizing feedback from high-level areas that represent holistic faces back to lower processing levels where detailed face features compete for conscious representation.


Assuntos
Reconhecimento Facial , Percepção Visual , Adulto , Feminino , Humanos , Masculino , Estimulação Luminosa , Visão Binocular , Adulto Jovem
7.
Neuron ; 95(1): 209-220.e3, 2017 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-28625487

RESUMO

The visual cortex is hierarchically organized, with low-level areas coding for simple features and higher areas for complex ones. Feedforward and feedback connections propagate information between areas in opposite directions, but their functional roles are only partially understood. We used electrical microstimulation to perturb the propagation of neuronal activity between areas V1 and V4 in monkeys performing a texture-segregation task. In both areas, microstimulation locally caused a brief phase of excitation, followed by inhibition. Both these effects propagated faithfully in the feedforward direction from V1 to V4. Stimulation of V4, however, caused little V1 excitation, but it did yield a delayed suppression during the late phase of visually driven activity. This suppression was pronounced for the V1 figure representation and weaker for background representations. Our results reveal functional differences between feedforward and feedback processing in texture segregation and suggest a specific modulating role for feedback connections in perceptual organization.


Assuntos
Retroalimentação , Córtex Visual/fisiologia , Animais , Estimulação Elétrica , Macaca mulatta , Masculino , Percepção Visual
8.
J Neurosci Methods ; 286: 38-55, 2017 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-28512008

RESUMO

BACKGROUND: Primate neurobiologists use chronically implanted devices such as pedestals for head stabilization and chambers to gain access to the brain and study its activity. Such implants are skull-mounted, and made from a hard, durable material, such as titanium. NEW METHOD: Here, we present a low-cost method of creating customized 3D-printed cranial implants that are tailored to the anatomy of individual animals. We performed pre-surgical computed tomography (CT) and magnetic resonance (MR) scans to generate three-dimensional (3D) models of the skull and brain. We then used 3D modelling software to design implantable head posts, chambers, and a pedestal anchorage base, as well as craniotomy guides to aid us during surgery. Prototypes were made from plastic or resin, while implants were 3D-printed in titanium. The implants underwent post-processing and received a coating of osteocompatible material to promote bone integration. RESULTS: Their tailored fit greatly facilitated surgical implantation, and eliminated the gap between the implant and the bone. To date, our implants remain robust and well-integrated with the skull. COMPARISON WITH EXISTING METHOD(S): Commercial-off-the-shelf solutions typically come with a uniform, flat base, preventing them from sitting flush against the curved surface of the skull. This leaves gaps for fluid and tissue ingress, increasing the risk of microbial infection and tissue inflammation, as well as implant loss. CONCLUSIONS: The use of 3D printing technology enabled us to quickly and affordably create unique, complex designs, avoiding the constraints levied by traditional production methods, thereby boosting experimental success and improving the wellbeing of the animals.


Assuntos
Encéfalo/diagnóstico por imagem , Cabeça/diagnóstico por imagem , Cabeça/cirurgia , Modelos Anatômicos , Impressão Tridimensional , Próteses e Implantes , Animais , Vasos Sanguíneos/diagnóstico por imagem , Encéfalo/cirurgia , Mapeamento Encefálico , Imageamento Tridimensional , Macaca mulatta , Masculino , Impressão Tridimensional/instrumentação , Tomografia Computadorizada por Raios X
9.
Trends Cogn Sci ; 21(2): 111-124, 2017 02.
Artigo em Inglês | MEDLINE | ID: mdl-28063661

RESUMO

Studies in humans and non-human primates have provided evidence for storage of working memory contents in multiple regions ranging from sensory to parietal and prefrontal cortex. We discuss potential explanations for these distributed representations: (i) features in sensory regions versus prefrontal cortex differ in the level of abstractness and generalizability; and (ii) features in prefrontal cortex reflect representations that are transformed for guidance of upcoming behavioral actions. We propose that the propensity to produce persistent activity is a general feature of cortical networks. Future studies may have to shift focus from asking where working memory can be observed in the brain to how a range of specialized brain areas together transform sensory information into a delayed behavioral response.


Assuntos
Memória de Curto Prazo/fisiologia , Córtex Pré-Frontal/fisiologia , Animais , Encéfalo , Mapeamento Encefálico , Humanos
13.
J Neurophysiol ; 108(8): 2101-14, 2012 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-22832573

RESUMO

Repeated stimulation impacts neuronal responses. Here we show how response characteristics of sensory neurons in macaque visual cortex are influenced by the duration of the interruptions during intermittent stimulus presentation. Besides effects on response magnitude consistent with neuronal adaptation, the response variability was also systematically influenced. Spike rate variability in motion-sensitive area MT decreased when interruption durations were systematically increased from 250 to 2,000 ms. Activity fluctuations between subsequent trials and Fano factors over full response sequences were both lower with longer interruptions, while spike timing patterns became more regular. These variability changes partially depended on the response magnitude, but another significant effect that was uncorrelated with adaptation-induced changes in response magnitude was also present. Reduced response variability was furthermore accompanied by changes in spike-field coherence, pointing to the possibility that reduced spiking variability results from interactions in the local cortical network. While neuronal response stabilization may be a general effect of repeated sensory stimulation, we discuss its potential link with the phenomenon of perceptual stabilization of ambiguous stimuli as a result of interrupted presentation.


Assuntos
Potenciais Evocados Visuais , Células Receptoras Sensoriais/fisiologia , Córtex Visual/fisiologia , Animais , Macaca mulatta , Masculino , Vias Neurais , Estimulação Luminosa , Células Receptoras Sensoriais/classificação , Córtex Visual/citologia , Percepção Visual
14.
PLoS One ; 7(3): e32786, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22403709

RESUMO

Catfish detect and identify invisible prey by sensing their ultra-weak electric fields with electroreceptors. Any neuron that deals with small-amplitude input has to overcome sensitivity limitations arising from inherent threshold non-linearities in spike-generation mechanisms. Many sensory cells solve this issue with stochastic resonance, in which a moderate amount of intrinsic noise causes irregular spontaneous spiking activity with a probability that is modulated by the input signal. Here we show that catfish electroreceptors have adopted a fundamentally different strategy. Using a reverse correlation technique in which we take spike interval durations into account, we show that the electroreceptors generate a supra-threshold bias current that results in quasi-periodically produced spikes. In this regime stimuli modulate the interval between successive spikes rather than the instantaneous probability for a spike. This alternative for stochastic resonance combines threshold-free sensitivity for weak stimuli with similar sensitivity for excitations and inhibitions based on single interspike intervals.


Assuntos
Eletricidade , Fenômenos Eletrofisiológicos , Ictaluridae/fisiologia , Modelos Neurológicos , Neurônios/citologia , Periodicidade , Animais , Estimulação Elétrica , Processos Estocásticos
15.
Atten Percept Psychophys ; 73(1): 219-36, 2011 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-21258921

RESUMO

Here, we investigate how audiovisual context affects perceived event duration with experiments in which observers reported which of two stimuli they perceived as longer. Target events were visual and/or auditory and could be accompanied by nontargets in the other modality. Our results demonstrate that the temporal information conveyed by irrelevant sounds is automatically used when the brain estimates visual durations but that irrelevant visual information does not affect perceived auditory duration (Experiment 1). We further show that auditory influences on subjective visual durations occur only when the temporal characteristics of the stimuli promote perceptual grouping (Experiments 1 and 2). Placed in the context of scalar expectancy theory of time perception, our third and fourth experiments have the implication that audiovisual context can lead both to changes in the rate of an internal clock and to temporal ventriloquism-like effects on perceived on- and offsets. Finally, intramodal grouping of auditory stimuli diminished any crossmodal effects, suggesting a strong preference for intramodal over crossmodal perceptual grouping (Experiment 5).


Assuntos
Associação , Atenção , Julgamento , Reconhecimento Visual de Modelos , Distorção da Percepção , Percepção da Altura Sonora , Percepção do Tempo , Adulto , Tomada de Decisões , Limiar Diferencial , Feminino , Humanos , Masculino , Psicofísica , Adulto Jovem
16.
Brain Res Rev ; 67(1-2): 56-72, 2011 Jun 24.
Artigo em Inglês | MEDLINE | ID: mdl-21059373

RESUMO

The majority of research on functional cerebral lateralization in primates revolves around vocal abilities, addressing the evolutionary origin of the human language faculty and its predominance in the left hemisphere of the brain. Right hemisphere specialization in spatial cognition is commonly reported in humans. This functional asymmetry is especially evident in the context of the unilateral neglect, a deficit in attention to and awareness of one side of space, that more frequently occurs after right-side rather than left-side brain damage. Since most of the research efforts are concentrated on vocalization in primates, much less is known about the presence or absence of spatial functions lateralization. Obtaining this knowledge can provide insight into the evolutionary aspect of the functionally lateralized brain of Homo sapiens and deliver refinement and validation of the nonhuman primate unilateral neglect model. This paper reviews the literature on functional brain asymmetries in processing spatial information, limiting the search to nonhuman primates, and concludes there is no clear evidence that monkeys process spatial information with different efficiency in the two hemispheres. We suggest that lateralization of spatial cognition in humans represents a relatively new feature on the evolutionary time scale, possibly developed as a by-product of the left hemisphere intrusion of language competence. Further, we argue that the monkey model of hemispatial neglect requires reconsideration.


Assuntos
Cérebro/fisiologia , Lateralidade Funcional/fisiologia , Primatas/fisiologia , Percepção Espacial/fisiologia , Animais , Evolução Biológica , Humanos , Transtornos da Percepção/fisiopatologia , Especificidade da Espécie
17.
J Neurophysiol ; 105(3): 1150-8, 2011 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-21177995

RESUMO

While neurons in posterior parietal cortex have been found to signal the presence of a salient stimulus among multiple items in a display, spatial summation within their receptive field in the absence of an attentional bias has never been investigated. This information, however, is indispensable when one investigates the mechanisms of spatial attention and competition between multiple visual objects. To examine the spatial summation rule in parietal area 7a neurons, we trained rhesus monkeys to fixate on a central cross while two identical stimuli were briefly displayed in a neuron's receptive field. The response to a pair of dots was compared with the responses to the same dots when they were presented individually. The scaling and power parameters of a generalized summation algorithm varied greatly, both across neurons and across combinations of stimulus locations. However, the averaged response of the recorded population of 7a neurons was consistent with a winner-take-all rule for spatial summation. A control experiment where a monkey covertly attended to both stimuli simultaneously suggests that attention introduces additional competition by facilitating the less optimal stimulus. Thus an averaging stage is introduced between ∼ 200 and 300 ms of the response to a pair of stimuli. In short, the summation algorithm over the population of area 7a neurons carries the signature of a winner-take-all operation, with spatial attention possibly influencing the temporal dynamics of stimulus competition, that is the moment that the "winner" takes "victory" over the "loser" stimulus.


Assuntos
Atenção/fisiologia , Sinais (Psicologia) , Tomada de Decisões/fisiologia , Rede Nervosa/fisiologia , Lobo Parietal/fisiologia , Mascaramento Perceptivo , Campos Visuais/fisiologia , Animais , Macaca mulatta , Masculino , Estimulação Luminosa/métodos
18.
Curr Biol ; 20(16): 1464-9, 2010 Aug 24.
Artigo em Inglês | MEDLINE | ID: mdl-20674360

RESUMO

Experience-driven neuronal plasticity allows the brain to adapt its functional connectivity to recent sensory input. Here we use binocular rivalry, an experimental paradigm in which conflicting images are presented to the individual eyes, to demonstrate plasticity in the neuronal mechanisms that convert visual information from two separated retinas into single perceptual experiences. Perception during binocular rivalry tended to initially consist of alternations between exclusive representations of monocularly defined images, but upon prolonged exposure, mixture percepts became more prevalent. The completeness of suppression, reflected in the incidence of mixture percepts, plausibly reflects the strength of inhibition that likely plays a role in binocular rivalry. Recovery of exclusivity was possible but required highly specific binocular stimulation. Documenting the prerequisites for these observed changes in perceptual exclusivity, our experiments suggest experience-driven plasticity at interocular inhibitory synapses, driven by the correlated activity (and also the lack thereof) of neurons representing the conflicting stimuli. This form of plasticity is consistent with a previously proposed but largely untested anti-Hebbian learning mechanism for inhibitory synapses in vision. Our results implicate experience-driven plasticity as one governing principle in the neuronal organization of binocular vision.


Assuntos
Visão Binocular/fisiologia , Humanos , Estimulação Luminosa , Disparidade Visual/fisiologia
19.
J Vis ; 9(10): 20.1-20, 2009 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-19810801

RESUMO

Local sensory information is often ambiguous forcing the brain to integrate spatiotemporally separated information for stable conscious perception. Lateral connections between clusters of similarly tuned neurons in the visual cortex are a potential neural substrate for the coupling of spatially separated visual information. Ecological optics suggests that perceptual coupling of visual information is particularly beneficial in occlusion situations. Here we present a novel neural network model and a series of human psychophysical experiments that can together explain the perceptual coupling of kinetic depth stimuli with activity-driven lateral information sharing in the far depth plane. Our most striking finding is the perceptual coupling of an ambiguous kinetic depth cylinder with a coaxially presented and disparity defined cylinder backside, while a similar frontside fails to evoke coupling. Altogether, our findings are consistent with the idea that clusters of similarly tuned far depth neurons share spatially separated motion information in order to resolve local perceptual ambiguities. The classification of far depth in the facilitation mechanism results from a combination of absolute and relative depth that suggests a functional role of these lateral connections in the perception of partially occluded objects.


Assuntos
Percepção de Profundidade/fisiologia , Modelos Neurológicos , Percepção de Movimento/fisiologia , Rede Nervosa , Simulação por Computador , Sinais (Psicologia) , Humanos , Cinética , Estimulação Luminosa/métodos , Psicofísica , Fatores de Tempo
20.
PLoS One ; 3(10): e3473, 2008.
Artigo em Inglês | MEDLINE | ID: mdl-18941522

RESUMO

The mechanisms underlying conscious visual perception are often studied with either binocular rivalry or perceptual rivalry stimuli. Despite existing research into both types of rivalry, it remains unclear to what extent their underlying mechanisms involve common computational rules. Computational models of binocular rivalry mechanisms are generally tested against Levelt's four propositions, describing the psychophysical relation between stimulus strength and alternation dynamics in binocular rivalry. Here we use a bistable rotating structure-from-motion sphere, a generally studied form of perceptual rivalry, to demonstrate that Levelt's propositions also apply to the alternation dynamics of perceptual rivalry. Importantly, these findings suggest that bistability in structure-from-motion results from active cross-inhibition between neural populations with computational principles similar to those present in binocular rivalry. Thus, although the neural input to the computational mechanism of rivalry may stem from different cortical neurons and different cognitive levels the computational principles just prior to the production of visual awareness appear to be common to the two types of rivalry.


Assuntos
Modelos Biológicos , Visão Binocular/fisiologia , Percepção Visual/fisiologia , Dominância Ocular , Lateralidade Funcional , Humanos , Mascaramento Perceptivo , Estimulação Luminosa , Disparidade Visual
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