The role of negative conductances in neuronal subthreshold properties and synaptic integration

Cesar C. Ceballos, Antonio C. Roque and Ricardo M. Leão

Based on passive cable theory, an increase in membrane conductance produces a decrease in the membrane time constant and input resistance. Unlike the classical leak currents, voltage-dependent currents have a nonlinear behavior which can create regions of negative conductance, despite the increase in membrane conductance (permeability). This negative conductance opposes the effects of the passive membrane conductance on the membrane input resistance and time constant, increasing their values and thereby substantially affecting the amplitude and time course of postsynaptic potentials at the voltage range of the negative conductance. This paradoxical effect has been described for three types of voltage-dependent inward currents: persistent sodium currents, L- and T-type calcium currents and ligand-gated glutamatergic N-methyl-D-aspartate currents. In this review, we describe the impact of the creation of a negative conductance region by these currents on neuronal membrane properties and synaptic integration. We also discuss recent contributions of the quasi-active cable approximation, an extension of the passive cable theory that includes voltage-dependent currents, and its effects on neuronal subthreshold properties.

Variability in functional brain networks predicts expertise during action observation

Amoruso L, Ibáñez A, Fonseca B, Gadea S, Sedeño L, Sigman M, García AM, Fraiman R, Fraiman D.

Observing an action performed by another individual activates, in the observer, similar circuits as those involved in the actual execution of that action. This activation is modulated by prior experience; indeed, sustained training in a particular motor domain leads to structural and functional changes in critical brain areas. Here, we capitalized on a novel graph-theory approach to electroencephalographic data (Fraiman et al., 2016) to test whether variability in functional brain networks implicated in Tango observation can discriminate between groups differing in their level of expertise. We found that experts and beginners significantly differed in the functional organization of task-relevant networks. Specifically, networks in expert Tango dancers exhibited less variability and a more robust functional architecture. Notably, these expertise-dependent effects were captured within networks derived from electrophysiological brain activity recorded in a very short time window (2s). In brief, variability in the organization of task-related networks seems to be a highly sensitive indicator of long-lasting training effects. This finding opens new methodological and theoretical windows to explore the impact of domain-specific expertise on brain plasticity, while highlighting variability as a fruitful measure in neuroimaging research.

Nota de repúdio à campanha difamatória da organização Wiki Educação Brasil

Em 6 de novembro, o Centro de Pesquisa, Inovação e Difusão em Neuromatemática (CEPID NeuroMat) foi surpreendido por uma campanha difamatória e um abaixo-assinado promovidos pela organização Wiki Educação Brasil contra a Universidade de São Paulo (USP) e o CEPID NeuroMat. O título do abaixo-assinado é: “USP, pare imediatamente de usar a justiça americana para tirar Wiki Brasil do ar!”; o documento está endereçado ao reitor da USP, a sua chefia de gabinete da USP, ao setor de Relações Internacionais da USP e a mim mesmo, enquanto coordenador do CEPID NeuroMat. A campanha e o abaixo-assinado foram difundidos globalmente em redes sociais, em fóruns de discussão, nos projetos Wikimedia e em cartas endereçadas a pesquisadores e militantes pela ciência aberta.

O CEPID NeuroMat repudia veementemente essa campanha e convoca a comunidade acadêmica a divulgar essa nota de repúdio.

Putting into discussion a research agenda: an assessment of the workshop on Random Structures in the Brain

NeuroMat held from October 16 to 20 the workshop "Random Structures in the Brain," that brought together most team members for presentations and discussions on the work the center engages with and for an effort to frame and consolidate directions for the years to come. The workshop was attended by over 60 NeuroMat members, including principal and associate investigators, senior and junior researchers and students. Leonardo Cohen (NIH/NINDS) and Wojciech Szpankowski (Purdue University), from NeuroMat's international advisory board, as well as international guest speakers Markus Diesmann (Research Centre Jüllich) and William Lytton (State University of New York) took part in the event.

1st AMPARO Workshop: First year of activities of the NeuroMat network to educate people with Parkinson's disease

Last October the International Parkinson and Movement Disorder Society published a text about the upcoming event of the NeuroMat initiative called "Rede Amparo". NeuroMat has a network to promote the collaboration of people living with Parkinson's disease, families and health professionals to face clinical and research challenges associated with Parkinson’s disease. This initiative, called AMPARO in Portuguese, is coordinated by the NeuroMat investigator Maria Elisa Pimentel Piemonte, a physical therapist and professor at the University of São Paulo in Brazil.

In its first year of activities AMPARO offered twelve lectures for people with Parkinson, their care partner and family about important issues an improve the quality of life. In parallel, AMPARO offered 12 lectures for health professionals about the interprofessional care in PD. All lectures are available in the AMPARO website and their key points are being published in the AMPARO Book 2017. International Parkinson and Movement Disorder Society (MDS) website, 23/10/2017. (In English)

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O Centro de Pesquisa, Inovação e Difusão em Neuromatemática está sediado na Universidade de São Paulo e é financiado pela FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo).

 

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