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1.
Brain Sci ; 14(7)2024 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-39061384

RESUMO

Motor intention is a high-level brain function related to planning for movement. Although studies have shown that motor intentions can be decoded from brain signals before movement execution, it is unclear whether intentions relating to mental imagery of movement can be decoded. Here, we investigated whether differences in spatial and temporal patterns of brain activation were elicited by intentions to perform different types of motor imagery and whether the patterns could be used by a multivariate pattern classifier to detect such differential intentions. The results showed that it is possible to decode intentions before the onset of different types of motor imagery from functional MR signals obtained from fronto-parietal brain regions, such as the premotor cortex and posterior parietal cortex, while controlling for eye movements and for muscular activity of the hands. These results highlight the critical role played by the aforementioned brain regions in covert motor intentions. Moreover, they have substantial implications for rehabilitating patients with motor disabilities.

3.
J Neurosci ; 42(33): 6469-6482, 2022 08 17.
Artigo em Inglês | MEDLINE | ID: mdl-35831173

RESUMO

Atypical sensory processing is now thought to be a core feature of the autism spectrum. Influential theories have proposed that both increased and decreased neural response reliability within sensory systems could underlie altered sensory processing in autism. Here, we report evidence for abnormally increased reliability of visual-evoked responses in layer 2/3 neurons of adult male and female primary visual cortex in the MECP2-duplication syndrome animal model of autism. Increased response reliability was due in part to decreased response amplitude, decreased fluctuations in endogenous activity, and an abnormal decoupling of visual-evoked activity from endogenous activity. Similar to what was observed neuronally, the optokinetic reflex occurred more reliably at low contrasts in mutant mice compared with controls. Retinal responses did not explain our observations. These data suggest that the circuit mechanisms for combining sensory-evoked and endogenous signal and noise processes may be altered in this form of syndromic autism.SIGNIFICANCE STATEMENT Atypical sensory processing is now thought to be a core feature of the autism spectrum. Influential theories have proposed that both increased and decreased neural response reliability within sensory systems could underlie altered sensory processing in autism. Here, we report evidence for abnormally increased reliability of visual-evoked responses in primary visual cortex of the animal model for MECP2-duplication syndrome, a high-penetrance single-gene cause of autism. Visual-evoked activity was abnormally decoupled from endogenous activity in mutant mice, suggesting in line with the influential "hypo-priors" theory of autism that sensory priors embedded in endogenous activity may have less influence on perception in autism.


Assuntos
Transtorno do Espectro Autista , Transtorno Autístico , Animais , Transtorno Autístico/genética , Modelos Animais de Doenças , Potenciais Evocados Visuais , Feminino , Masculino , Deficiência Intelectual Ligada ao Cromossomo X , Proteína 2 de Ligação a Metil-CpG/genética , Camundongos , Córtex Visual Primário , Reprodutibilidade dos Testes
4.
PLoS Pathog ; 17(12): e1010092, 2021 12.
Artigo em Inglês | MEDLINE | ID: mdl-34914812

RESUMO

The development of safe and effective vaccines to prevent SARS-CoV-2 infections remains an urgent priority worldwide. We have used a recombinant vesicular stomatitis virus (rVSV)-based prime-boost immunization strategy to develop an effective COVID-19 vaccine candidate. We have constructed VSV genomes carrying exogenous genes resulting in the production of avirulent rVSV carrying the full-length spike protein (SF), the S1 subunit, or the receptor-binding domain (RBD) plus envelope (E) protein of SARS-CoV-2. Adding the honeybee melittin signal peptide (msp) to the N-terminus enhanced the protein expression, and adding the VSV G protein transmembrane domain and the cytoplasmic tail (Gtc) enhanced protein incorporation into pseudotype VSV. All rVSVs expressed three different forms of SARS-CoV-2 spike proteins, but chimeras with VSV-Gtc demonstrated the highest rVSV-associated expression. In immunized mice, rVSV with chimeric S protein-Gtc derivatives induced the highest level of potent neutralizing antibodies and T cell responses, and rVSV harboring the full-length msp-SF-Gtc proved to be the superior immunogen. More importantly, rVSV-msp-SF-Gtc vaccinated animals were completely protected from a subsequent SARS-CoV-2 challenge. Overall, we have developed an efficient strategy to induce a protective response in SARS-CoV-2 challenged immunized mice. Vaccination with our rVSV-based vector may be an effective solution in the global fight against COVID-19.


Assuntos
Enzima de Conversão de Angiotensina 2/metabolismo , Anticorpos Neutralizantes/imunologia , Anticorpos Antivirais/imunologia , Vacinas contra COVID-19/administração & dosagem , COVID-19/prevenção & controle , Glicoproteína da Espícula de Coronavírus/imunologia , Vírus da Estomatite Vesicular Indiana/genética , Enzima de Conversão de Angiotensina 2/genética , Animais , COVID-19/imunologia , COVID-19/virologia , Vacinas contra COVID-19/genética , Chlorocebus aethiops , Humanos , Imunização , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , SARS-CoV-2/imunologia , Glicoproteína da Espícula de Coronavírus/genética , Glicoproteína da Espícula de Coronavírus/metabolismo , Células Vero , Proteínas Virais/genética , Proteínas Virais/imunologia
5.
J Gen Virol ; 102(4)2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33913804

RESUMO

The development of a vaccine to prevent Zika virus (ZIKV) infection has been one of the priorities in infectious disease research in recent years. There have been numerous attempts to develop an effective vaccine against ZIKV. It is imperative to choose the safest and the most effective ZIKV vaccine from all candidate vaccines to control this infection globally. We have employed a dual serotype of prime-boost recombinant vesicular stomatitis virus (VSV) vaccine strategy, to develop a ZIKV vaccine candidate, using a type 1 IFN-receptor knock-out (Ifnar-/-) mouse model for challenge studies. Prime vaccination with an attenuated recombinant VSV Indiana serotype (rVSVInd) carrying a genetically modified ZIKV envelope (E) protein gene followed by boost vaccination with attenuated recombinant VSV New Jersey serotype (rVSVNJ) carrying the same E gene induced robust adaptive immune responses. In particular, rVSV carrying the ZIKV E gene with the honeybee melittin signal peptide (msp) at the N terminus and VSV G protein transmembrane domain and cytoplasmic tail (Gtc) at the C terminus of the E gene induced strong protective immune responses. This vaccine regimen induced highly potent neutralizing antibodies and T cell responses in the absence of an adjuvant and protected Ifnar-/- mice from a lethal dose of the ZIKV challenge.


Assuntos
Vírus da Estomatite Vesicular New Jersey/imunologia , Proteínas do Envelope Viral/imunologia , Vacinas Virais/imunologia , Infecção por Zika virus/prevenção & controle , Animais , Anticorpos Neutralizantes/sangue , Anticorpos Antivirais/sangue , Chlorocebus aethiops , Cricetinae , Células HEK293 , Humanos , Imunidade , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Células Vero
6.
PeerJ ; 8: e10429, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33354420

RESUMO

Turbidity currents are the main drivers behind the transportation of terrestrial sediments to the deep sea, and turbidite deposits from such currents have been widely used in geological studies. Nevertheless, the contribution of turbidity currents to vertical displacement of seawater has rarely been discussed. This is partly because until recently, deep-sea turbidity currents have rarely been observed due to their unpredictable nature, being usually triggered by meteorological or geological events such as typhoons and earthquakes. Here, we report a direct observation of a deep-sea turbidity current using the recently developed Edokko Mark 1 monitoring system deployed in 2019 at a depth of 1,370 m in Suruga Bay, central Japan. A turbidity current occurred two days after its probable cause, the Super Typhoon Hagibis (2019), passed through Suruga Bay causing devastating damage. Over aperiod of 40 hours, we observed increased turbidity with turbulent conditions confirmed by a video camera. The turbidity exhibited two sharp peaks around 3:00 and 11:00 on October 14 (Japan Standard Time). The temperature and salinity characteristics during these high turbidity events agreed with independent measurements for shallow water layers in Suruga Bay at the same time, strongly suggesting that the turbidity current caused vertical displacement in the bay's water column by transporting warmer and shallower waters downslope of the canyon. Our results add to the previous few examples that show meteorological and geological events may have significant contributions in the transportation of shallower seawater to the deep sea. Recent technological developments pertaining to the Edokko Mark 1 and similar devices enable straightforward, long-term monitoring of the deep-seafloor and will contribute to the understanding of similar spontaneous events in the deep ocean.

7.
J Neurosci ; 39(9): 1671-1687, 2019 02 27.
Artigo em Inglês | MEDLINE | ID: mdl-30647148

RESUMO

Neurons in primary visual cortex are strongly modulated both by stimulus contrast and by fluctuations of internal inputs. An important question is whether the population code is preserved under these conditions. Changes in stimulus contrast are thought to leave the population code invariant, whereas the effect of internal gain modulations remains unknown. To address these questions we studied how the direction-of-motion of oriented gratings is encoded in layer 2/3 primary visual cortex of mouse (with C57BL/6 background, of either sex). We found that, because contrast gain responses across cells are heterogeneous, a change in contrast alters the information distribution profile across cells leading to a violation of contrast invariance. Remarkably, internal input fluctuations that cause commensurate firing rate modulations at the single-cell level result in more homogeneous gain responses, respecting population code invariance. These observations argue that the brain strives to maintain the stability of the neural code in the face of fluctuating internal inputs.SIGNIFICANCE STATEMENT Neuronal responses are modulated both by stimulus contrast and by the spontaneous fluctuation of internal inputs. It is not well understood how these different types of input impact the population code. Specifically, it is important to understand whether the neural code stays invariant in the face of significant internal input modulations. Here, we show that changes in stimulus contrast lead to different optimal population codes, whereas spontaneous internal input fluctuations leave the population code invariant. This is because spontaneous internal input fluctuations modulate the gain of neuronal responses more homogeneously across cells compared to changes in stimulus contrast.


Assuntos
Córtex Visual/fisiologia , Percepção Visual , Animais , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Modelos Neurológicos , Neurônios/fisiologia , Córtex Visual/citologia
8.
Oncotarget ; 9(9): 8334-8349, 2018 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-29492199

RESUMO

Genetically engineered mouse models have proven to be essential tools for unraveling fundamental aspects of cancer biology and for testing novel therapeutic strategies. To optimally serve these goals, it is essential that the mouse model faithfully recapitulates the human disease. Recently, novel mouse models for neuroblastoma have been developed. Here, we report on the further genomic characterization through exome sequencing and DNA copy number analysis of four of the currently available murine neuroblastoma model systems (ALK, Th-MYCN, Dbh-MYCN and Lin28b). The murine tumors revealed a low number of genomic alterations - in keeping with human neuroblastoma - and a positive correlation of the number of genetic lesions with the time to onset of tumor formation was observed. Gene copy number alterations are the hallmark of both murine and human disease and frequently affect syntenic genomic regions. Despite low mutational load, the genes mutated in murine disease were found to be enriched for genes mutated in human disease. Taken together, our study further supports the validity of the tested mouse models for mechanistic and preclinical studies of human neuroblastoma.

9.
Front Neural Circuits ; 11: 50, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28785207

RESUMO

Cortical neuropil modulations recorded by calcium imaging reflect the activity of large aggregates of axo-dendritic processes and synaptic compartments from a large number of neurons. The organization of this activity impacts neuronal firing but is not well understood. Here we used in vivo 2-photon imaging with Oregon Green Bapta (OGB) and GCaMP6s to study neuropil visual responses to moving gratings in layer 2/3 of mouse area V1. We found neuropil responses to be strongly modulated and more reliable than neighboring somatic activity. Furthermore, stimulus independent modulations in neuropil activity, i.e., noise correlations, were highly coherent across the cortical surface, up to distances of at least 200 µm. Pairwise neuropil-to-neuropil-patch noise correlation strength was much higher than cell-to-cell noise correlation strength and depended strongly on brain state, decreasing in quiet wakefulness relative to light anesthesia. The profile of neuropil noise correlation strength decreased gently with distance, dropping by ~11% at a distance of 200 µm. This was comparatively slower than the profile of cell-to-cell noise correlations, which dropped by ~23% at 200 µm. Interestingly, in spite of the "salt & pepper" organization of orientation and direction encoding across mouse V1 neurons, populations of neuropil patches, even of moderately large size (radius ~100 µm), showed high accuracy for discriminating perpendicularly moving gratings. This was commensurate to the accuracy of corresponding cell populations. The dynamic, stimulus dependent, nature of neuropil activity further underscores the need to carefully separate neuropil from cell soma activity in contemporary imaging studies.


Assuntos
Neurópilo/fisiologia , Transmissão Sináptica/fisiologia , Córtex Visual/fisiologia , Percepção Visual/fisiologia , Algoritmos , Animais , Cálcio/metabolismo , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Neurópilo/citologia , Neurópilo/efeitos dos fármacos , Técnicas de Patch-Clamp , Estimulação Luminosa , Processamento de Sinais Assistido por Computador , Transmissão Sináptica/efeitos dos fármacos , Córtex Visual/citologia , Córtex Visual/efeitos dos fármacos , Percepção Visual/efeitos dos fármacos , Imagens com Corantes Sensíveis à Voltagem , Vigília/efeitos dos fármacos , Vigília/fisiologia
10.
Front Neurosci ; 11: 237, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28496399

RESUMO

Kahneman and Tversky (1979) first demonstrated that when individuals decide whether or not to accept a gamble, potential losses receive more weight than possible gains in the decision. This phenomenon is referred to as loss aversion. We investigated how loss aversion in risky financial decisions is influenced by sudden changes to wealth, employing both behavioral and neurobiological measures. We implemented an fMRI experimental paradigm, based on that employed by Tom et al. (2007). There are two treatments, called RANDOM and CONTINGENT. In RANDOM, the baseline setting, the changes to wealth, referred to as wealth shocks in economics, are independent of the actual choices participants make. Under CONTINGENT, we induce the belief that the changes in income are a consequence of subjects' own decisions. The magnitudes and sequence of the shocks to wealth are identical between the CONTINGENT and RANDOM treatments. We investigated whether more loss aversion existed in one treatment than another. The behavioral results showed significantly greater loss aversion in CONTINGENT compared to RANDOM after a negative wealth shock. No differences were observed in the response to positive shocks. The fMRI results revealed a neural loss aversion network, comprising the bilateral striatum, amygdala and dorsal anterior cingulate cortex that was common to the CONTINGENT and RANDOM tasks. However, the ventral prefrontal cortex, primary somatosensory cortex and superior occipital cortex, showed greater activation in response to a negative change in wealth due to individual's own decisions than when the change was exogenous. These results indicate that striatum activation correlates with loss aversion independently of the source of the shock, and that the ventral prefrontal cortex (vPFC) codes the experimental manipulation of agency in one's actions influencing loss aversion.

11.
Retrovirology ; 13(1): 82, 2016 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-27894306

RESUMO

BACKGROUND: Vaccination with inactivated (killed) whole-virus particles has been used to prevent a wide range of viral diseases. However, for an HIV vaccine this approach has been largely negated due to inherent safety concerns, despite the ability of killed whole-virus vaccines to generate a strong, predominantly antibody-mediated immune response in vivo. HIV-1 Clade B NL4-3 was genetically modified by deleting the nef and vpu genes and substituting the coding sequence for the Env signal peptide with that of honeybee melittin signal peptide to produce a less virulent and more replication efficient virus. This genetically modified virus (gmHIV-1NL4-3) was inactivated and formulated as a killed whole-HIV vaccine, and then used for a Phase I human clinical trial (Trial Registration: Clinical Trials NCT01546818). The gmHIV-1NL4-3 was propagated in the A3.01 human T cell line followed by virus purification and inactivation with aldrithiol-2 and γ-irradiation. Thirty-three HIV-1 positive volunteers receiving cART were recruited for this observer-blinded, placebo-controlled Phase I human clinical trial to assess the safety and immunogenicity. RESULTS: Genetically modified and killed whole-HIV-1 vaccine, SAV001, was well tolerated with no serious adverse events. HIV-1NL4-3-specific PCR showed neither evidence of vaccine virus replication in the vaccine virus-infected human T lymphocytes in vitro nor in the participating volunteers receiving SAV001 vaccine. Furthermore, SAV001 with adjuvant significantly increased the pre-existing antibody response to HIV-1 proteins. Antibodies in the plasma of vaccinees were also found to recognize HIV-1 envelope protein on the surface of infected cells as well as showing an enhancement of broadly neutralizing antibodies inhibiting tier I and II of HIV-1 B, D, and A subtypes. CONCLUSION: The killed whole-HIV vaccine, SAV001, is safe and triggers anti-HIV immune responses. It remains to be determined through an appropriate trial whether this immune response prevents HIV infection.


Assuntos
Vacinas contra a AIDS , Anticorpos Neutralizantes/sangue , Anticorpos Anti-HIV/sangue , Infecções por HIV/prevenção & controle , HIV-1/imunologia , Imunogenicidade da Vacina , Vacinas contra a AIDS/administração & dosagem , Vacinas contra a AIDS/efeitos adversos , Vacinas contra a AIDS/imunologia , Adulto , Animais , Anticorpos Neutralizantes/imunologia , Abelhas/genética , Feminino , Produtos do Gene nef/genética , Anticorpos Anti-HIV/imunologia , Infecções por HIV/imunologia , HIV-1/genética , Proteínas do Vírus da Imunodeficiência Humana/genética , Humanos , Masculino , Pessoa de Meia-Idade , Sinais Direcionadores de Proteínas , Vacinas de Produtos Inativados/administração & dosagem , Vacinas de Produtos Inativados/efeitos adversos , Vacinas de Produtos Inativados/imunologia , Proteínas Virais Reguladoras e Acessórias/genética , Adulto Jovem
12.
Neuroimage ; 120: 176-90, 2015 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-26146195

RESUMO

There is extensive controversy over whether the adult visual cortex is able to reorganize following visual field loss (scotoma) as a result of retinal or cortical lesions. Functional magnetic resonance imaging (fMRI) methods provide a useful tool to study the aggregate receptive field properties and assess the capacity of the human visual cortex to reorganize following injury. However, these methods are prone to biases near the boundaries of the scotoma. Retinotopic changes resembling reorganization have been observed in the early visual cortex of normal subjects when the visual stimulus is masked to simulate retinal or cortical scotomas. It is not known how the receptive fields of higher visual areas, like hV5/MT+, are affected by partial stimulus deprivation. We measured population receptive field (pRF) responses in human area V5/MT+ of 5 healthy participants under full stimulation and compared them with responses obtained from the same area while masking the left superior quadrant of the visual field ("artificial scotoma" or AS). We found that pRF estimations in area hV5/MT+ are nonlinearly affected by the AS. Specifically, pRF centers shift towards the AS, while the pRF amplitude increases and the pRF size decreases near the AS border. The observed pRF changes do not reflect reorganization but reveal important properties of normal visual processing under different test-stimulus conditions.


Assuntos
Imageamento por Ressonância Magnética/métodos , Reconhecimento Visual de Modelos/fisiologia , Escotoma/fisiopatologia , Córtex Visual/fisiologia , Campos Visuais/fisiologia , Adulto , Idoso , Feminino , Voluntários Saudáveis , Humanos , Masculino , Pessoa de Meia-Idade , Adulto Jovem
13.
Nat Genet ; 47(8): 872-7, 2015 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-26121086

RESUMO

Neuroblastoma is a malignancy of the developing sympathetic nervous system that is often lethal when relapse occurs. We here used whole-exome sequencing, mRNA expression profiling, array CGH and DNA methylation analysis to characterize 16 paired samples at diagnosis and relapse from individuals with neuroblastoma. The mutational burden significantly increased in relapsing tumors, accompanied by altered mutational signatures and reduced subclonal heterogeneity. Global allele frequencies at relapse indicated clonal mutation selection during disease progression. Promoter methylation patterns were consistent over disease course and were patient specific. Recurrent alterations at relapse included mutations in the putative CHD5 neuroblastoma tumor suppressor, chromosome 9p losses, DOCK8 mutations, inactivating mutations in PTPN14 and a relapse-specific activity pattern for the PTPN14 target YAP. Recurrent new mutations in HRAS, KRAS and genes mediating cell-cell interaction in 13 of 16 relapse tumors indicate disturbances in signaling pathways mediating mesenchymal transition. Our data shed light on genetic alteration frequency, identity and evolution in neuroblastoma.


Assuntos
Regulação Neoplásica da Expressão Gênica , Mutação , Recidiva Local de Neoplasia/genética , Neuroblastoma/genética , Proteínas Adaptadoras de Transdução de Sinal/genética , Linhagem Celular Tumoral , Hibridização Genômica Comparativa , Variações do Número de Cópias de DNA , DNA Helicases/genética , Exoma/genética , Perfilação da Expressão Gênica/métodos , Frequência do Gene , Fatores de Troca do Nucleotídeo Guanina/genética , Via de Sinalização Hippo , Humanos , Hibridização in Situ Fluorescente , Proteínas do Tecido Nervoso/genética , Neuroblastoma/patologia , Análise de Sequência com Séries de Oligonucleotídeos , Fosfoproteínas/genética , Proteínas Serina-Treonina Quinases/genética , Proteínas Tirosina Fosfatases não Receptoras/genética , Análise de Sequência de DNA/métodos , Transdução de Sinais/genética , Fatores de Transcrição , Proteínas de Sinalização YAP
14.
Oncotarget ; 6(17): 15425-35, 2015 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-26029996

RESUMO

Dysregulation of the cell cycle and cyclin-dependent kinases (cdks) is a hallmark of cancer cells. Intervention with cdk function is currently evaluated as a therapeutic option in many cancer types including neuroblastoma (NB), a common solid tumor of childhood. Re-analyses of mRNA profiling data from primary NB revealed that high level mRNA expression of both cdk1 and its corresponding cyclin, CCNB1, were significantly associated with worse patient outcome independent of MYCN amplification, a strong indicator of adverse NB prognosis. Cdk1 as well as CCNB1 expression were readily detectable in all embryonal tumor cell lines investigated. Pharmacological inhibition or siRNA-mediated knockdown of cdk1/CCNB1 induced proliferation arrest independent of MYCN status in NB cells. Sensitivity to cdk1 inhibition was modulated by TP53, which was demonstrated using isogenic cells with wild-type TP53 expressing either dominant-negative p53 or a short hairpin RNA directed against TP53. Apoptosis induced by cdk1 inhibition was dependent on caspase activation and was concomitant with upregulation of transcriptional targets of TP53. Our results confirm an essential role for the cdk1/CCNB1 complex in tumor cell survival. As relapsing embryonal tumors often present with p53 pathway alterations, these findings have potential implications for therapy approaches targeting cdks.


Assuntos
Ciclina B1/antagonistas & inibidores , Quinases Ciclina-Dependentes/antagonistas & inibidores , Neuroblastoma/patologia , Rabdomiossarcoma/patologia , Proteína Supressora de Tumor p53/metabolismo , Apoptose/efeitos dos fármacos , Apoptose/genética , Proteína Quinase CDC2 , Caspase 8/metabolismo , Caspase 9/metabolismo , Proliferação de Células/genética , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/genética , Ciclina B1/genética , Quinases Ciclina-Dependentes/genética , Ativação Enzimática/efeitos dos fármacos , Pontos de Checagem da Fase G2 do Ciclo Celular/efeitos dos fármacos , Humanos , Lactente , Proteína Proto-Oncogênica N-Myc , Proteínas Nucleares/genética , Proteínas Oncogênicas/genética , Quinolinas/farmacologia , Interferência de RNA , RNA Mensageiro/genética , RNA Interferente Pequeno , Tiazóis/farmacologia , Células Tumorais Cultivadas , Proteína Supressora de Tumor p53/genética
15.
J Vis Exp ; (96)2015 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-25741774

RESUMO

Visual cortex is retinotopically organized so that neighboring populations of cells map to neighboring parts of the visual field. Functional magnetic resonance imaging allows us to estimate voxel-based population receptive fields (pRF), i.e., the part of the visual field that activates the cells within each voxel. Prior, direct, pRF estimation methods(1) suffer from certain limitations: 1) the pRF model is chosen a-priori and may not fully capture the actual pRF shape, and 2) pRF centers are prone to mislocalization near the border of the stimulus space. Here a new topographical pRF estimation method(2) is proposed that largely circumvents these limitations. A linear model is used to predict the Blood Oxygen Level-Dependent (BOLD) signal by convolving the linear response of the pRF to the visual stimulus with the canonical hemodynamic response function. PRF topography is represented as a weight vector whose components represent the strength of the aggregate response of voxel neurons to stimuli presented at different visual field locations. The resulting linear equations can be solved for the pRF weight vector using ridge regression(3), yielding the pRF topography. A pRF model that is matched to the estimated topography can then be chosen post-hoc, thereby improving the estimates of pRF parameters such as pRF-center location, pRF orientation, size, etc. Having the pRF topography available also allows the visual verification of pRF parameter estimates allowing the extraction of various pRF properties without having to make a-priori assumptions about the pRF structure. This approach promises to be particularly useful for investigating the pRF organization of patients with disorders of the visual system.


Assuntos
Imageamento por Ressonância Magnética/métodos , Córtex Visual/fisiologia , Campos Visuais/fisiologia , Mapeamento Encefálico/métodos , Humanos , Modelos Neurológicos , Neurônios/fisiologia , Orientação , Estimulação Luminosa/métodos
16.
PLoS One ; 9(10): e108818, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25295525

RESUMO

Identifying relevant signatures for clinical patient outcome is a fundamental task in high-throughput studies. Signatures, composed of features such as mRNAs, miRNAs, SNPs or other molecular variables, are often non-overlapping, even though they have been identified from similar experiments considering samples with the same type of disease. The lack of a consensus is mostly due to the fact that sample sizes are far smaller than the numbers of candidate features to be considered, and therefore signature selection suffers from large variation. We propose a robust signature selection method that enhances the selection stability of penalized regression algorithms for predicting survival risk. Our method is based on an aggregation of multiple, possibly unstable, signatures obtained with the preconditioned lasso algorithm applied to random (internal) subsamples of a given cohort data, where the aggregated signature is shrunken by a simple thresholding strategy. The resulting method, RS-PL, is conceptually simple and easy to apply, relying on parameters automatically tuned by cross validation. Robust signature selection using RS-PL operates within an (external) subsampling framework to estimate the selection probabilities of features in multiple trials of RS-PL. These probabilities are used for identifying reliable features to be included in a signature. Our method was evaluated on microarray data sets from neuroblastoma, lung adenocarcinoma, and breast cancer patients, extracting robust and relevant signatures for predicting survival risk. Signatures obtained by our method achieved high prediction performance and robustness, consistently over the three data sets. Genes with high selection probability in our robust signatures have been reported as cancer-relevant. The ordering of predictor coefficients associated with signatures was well-preserved across multiple trials of RS-PL, demonstrating the capability of our method for identifying a transferable consensus signature. The software is available as an R package rsig at CRAN (http://cran.r-project.org).


Assuntos
Algoritmos , Neoplasias/mortalidade , Neoplasias da Mama/mortalidade , Humanos , Modelos Teóricos , Neuroblastoma/mortalidade , Modelos de Riscos Proporcionais
17.
J Nanosci Nanotechnol ; 13(12): 7932-7, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-24266167

RESUMO

We fabricated dual-beam cantilevers on the microelectromechanical system (MEMS) scale with an integrated Si proof mass. A Pb(Zr,Ti)O3 (PZT) cantilever was designed as a mechanical vibration energy-harvesting system for low power applications. The resonant frequency of the multilayer composition cantilevers were simulated using the finite element method (FEM) with parametric analysis carried out in the design process. According to simulations, the resonant frequency, voltage, and average power of a dual-beam cantilever was 69.1 Hz, 113.9 mV, and 0.303 microW, respectively, at optimal resistance and 0.5 g (gravitational acceleration, m/s2). Based on these data, we subsequently fabricated cantilever devices using dual-beam cantilevers. The harvested power density of the dual-beam cantilever compared favorably with the simulation. Experiments revealed the resonant frequency, voltage, and average power density to be 78.7 Hz, 118.5 mV, and 0.34 microW, respectively. The error between the measured and simulated results was about 10%. The maximum average power and power density of the fabricated dual-beam cantilever at 1 g were 0.803 microW and 1322.80 microW cm(-3), respectively. Furthermore, the possibility of a MEMS-scale power source for energy conversion experiments was also tested.

18.
Front Neurosci ; 7: 170, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24151454

RESUMO

There is a recent increase in the use of multivariate analysis and pattern classification in prediction and real-time feedback of brain states from functional imaging signals and mapping of spatio-temporal patterns of brain activity. Here we present MANAS, a generalized software toolbox for performing online and offline classification of fMRI signals. MANAS has been developed using MATLAB, LIBSVM, and SVMlight packages to achieve a cross-platform environment. MANAS is targeted for neuroscience investigations and brain rehabilitation applications, based on neurofeedback and brain-computer interface (BCI) paradigms. MANAS provides two different approaches for real-time classification: subject dependent and subject independent classification. In this article, we present the methodology of real-time subject dependent and subject independent pattern classification of fMRI signals; the MANAS software architecture and subsystems; and finally demonstrate the use of the system with experimental results.

19.
Neuroimage ; 81: 144-157, 2013 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-23684878

RESUMO

We introduce a new method for measuring visual population receptive fields (pRF) with functional magnetic resonance imaging (fMRI). The pRF structure is modeled as a set of weights that can be estimated by solving a linear model that predicts the Blood Oxygen Level-Dependent (BOLD) signal using the stimulus protocol and the canonical hemodynamic response function. This method does not make a priori assumptions about the specific pRF shape and is therefore a useful tool for uncovering the underlying pRF structure at different spatial locations in an unbiased way. We show that our method is more accurate than a previously described method (Dumoulin and Wandell, 2008) which directly fits a 2-dimensional isotropic Gaussian pRF model to predict the fMRI time-series. We demonstrate that direct-fit models do not fully capture the actual pRF shape, and can be prone to pRF center mislocalization when the pRF is located near the border of the stimulus space. A quantitative comparison demonstrates that our method outperforms the direct-fit methods in the pRF center modeling by achieving higher explained variance of the BOLD signal. This was true for direct-fit isotropic Gaussian, anisotropic Gaussian, and difference of isotropic Gaussians model. Importantly, our model is also capable of exploring a variety of pRF properties such as surround suppression, receptive field center elongation, orientation, location and size. Additionally, the proposed method is particularly attractive for monitoring pRF properties in the visual areas of subjects with lesions of the visual pathways, where it is difficult to anticipate what shape the reorganized pRF might take. Finally, the method proposed here is more efficient in computation time than direct-fit methods, which need to search for a set of parameters in an extremely large searching space. Instead, this method uses the pRF topography to constrain the space that needs to be searched for the subsequent modeling.


Assuntos
Algoritmos , Mapeamento Encefálico/métodos , Imageamento por Ressonância Magnética/métodos , Córtex Visual/fisiologia , Campos Visuais/fisiologia , Adulto , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Masculino , Estimulação Luminosa , Adulto Jovem
20.
Hum Brain Mapp ; 34(1): 200-12, 2013 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-22021045

RESUMO

Real-time functional magnetic resonance imaging (rtfMRI) is a novel technique that has allowed subjects to achieve self-regulation of circumscribed brain regions. Despite its anticipated therapeutic benefits, there is no report on successful application of this technique in psychiatric populations. The objectives of the present study were to train schizophrenia patients to achieve volitional control of bilateral anterior insula cortex on multiple days, and to explore the effect of learned self-regulation on face emotion recognition (an extensively studied deficit in schizophrenia) and on brain network connectivity. Nine patients with schizophrenia were trained to regulate the hemodynamic response in bilateral anterior insula with contingent rtfMRI neurofeedback, through a 2-weeks training. At the end of the training stage, patients performed a face emotion recognition task to explore behavioral effects of learned self-regulation. A learning effect in self-regulation was found for bilateral anterior insula, which persisted through the training. Following successful self-regulation, patients recognized disgust faces more accurately and happy faces less accurately. Improvements in disgust recognition were correlated with levels of self-activation of right insula. RtfMRI training led to an increase in the number of the incoming and outgoing effective connections of the anterior insula. This study shows for the first time that patients with schizophrenia can learn volitional brain regulation by rtfMRI feedback training leading to changes in the perception of emotions and modulations of the brain network connectivity. These findings open the door for further studies of rtfMRI in severely ill psychiatric populations, and possible therapeutic applications.


Assuntos
Emoções/fisiologia , Imageamento por Ressonância Magnética/métodos , Neurorretroalimentação/métodos , Esquizofrenia/fisiopatologia , Esquizofrenia/terapia , Volição/fisiologia , Adulto , Mapeamento Encefálico/métodos , Córtex Cerebral/citologia , Córtex Cerebral/fisiologia , Face , Expressão Facial , Feminino , Humanos , Masculino , Modelos Neurológicos , Vias Neurais/fisiologia , Reconhecimento Visual de Modelos/fisiologia , Estimulação Luminosa/métodos , Reconhecimento Psicológico/fisiologia , Adulto Jovem
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