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Adult neurogenesis persists in the adult hippocampus due to the presence of multipotent neural stem cells (NSCs). Hippocampal neurogenesis is involved in a range of cognitive functions and is tightly regulated by neuronal activity. NSCs respond promptly to physiological and pathological stimuli altering their neurogenic and gliogenic potential. In a mouse model of mesial temporal lobe epilepsy (MTLE), seizures triggered by the intrahippocampal injection of the glutamate receptor agonist kainic acid (KA) induce NSCs to convert into reactive NSCs (React-NSCs) which stop producing new neurons and ultimately generate reactive astrocytes thus contributing to the development of hippocampal sclerosis and abolishing neurogenesis. We herein show how seizures triggered by the injection of KA in the amygdala, an alternative model of MTLE which allows parallel experimental manipulation in the dentate gyrus, also trigger the induction of React-NSCs and provoke the disruption of the neurogenic niche resulting in impaired neurogenesis. These results highlight the sensitivity of NSCs to the surrounding neuronal circuit activity and demonstrate that the induction of React-NSCs and the disruption of the neurogenic niche are not due to the direct effect of KA in the hippocampus. These results also suggest that neurogenesis might be lost in the hippocampus of patients with MTLE. Indeed we provide results from human MTLE samples absence of cell proliferation, of neural stem cell-like cells and of neurogenesis.

“Ojalá nos alcance la vida… para sembrar, argumentar y defender la paz”. Estas historias de vida se refieren al dolor, a la fortaleza y a la esperanza de personas mayores víctimas del conflicto armado en Colombia. Son experiencias que nos invitan a reconocer las particularidades que enfrentan las personas mayores en contextos de violencia, a reflexionar sobre la larga duración de la confrontación armada, pero sobre todo, a visibilizar sus posibilidades de aportar en entornos familiares, comunitarios y nacionales a la edificación de un nuevo país. Las voces de las personas mayores son indispensables para la reconstrucción de la memoria histórica, son un llamado sobre las transformaciones que necesitamos en el presente para envejecer de otros modos. Descripción tomada de: http://www.centrodememoriahistorica.gov.co/informes-2017/ojala-nos-alcance-la-vida, OJALÁ NOS ALCANCE LA VIDA Historias de vida de personas mayores víctimas del conflicto armado colombiano OJALÁ NOS ALCANCE LA VIDA HISTORIAS DE VIDA DE PERSONAS MAYORES VÍCTIMAS DEL CONFLICTO ARMADO COLOMBIANO OJALÁ NOS ALCANCE LA VIDA HISTORIAS DE VIDA DE PERSONAS MAYORES VÍCTIMAS DEL CONFLICTO ARMADO COLOMBIANO Gladys Orozco Soto Esperanza Trujillo Uribe Irene Muñoz de Benavides Ángela Sanabria González Luz Gladyz Tabares O. Rubén Darío Zapata Paul Alzate Flórez Julio Casas Castro Rodrigo Callejas Bedoya Nelson Hoyos Espinosa Héctor Tabares O. María Tila Uribe Investigación, entrevistas y redacción Héctor Tabares Ortiz Coordinador – Editor general Corporación Asuntos Mayores – COASUMA Javier Darío Restrepo Diana Durán Edición de contenido Javier Darío Restrepo María Tila Uribe Prólogo y posfacio María Tila Uribe Javier Darío Restrepo Héctor Tabares Ortiz Nayibe Lizeth Sánchez Rodríguez (Enfoque de Personas Mayores - CNMH) Marlon Ricardo Acuña Rivera (Enfoque de Personas Mayores - CNMH) Ángela Sanabria González (HelpAge International Colombia) Equipo de trabajo CENTRO NACIONAL DE MEMORIA HISTÓRICA Gonzalo Sánchez Gómez Director General Camila Medina Arbeláez Dirección para la Construcción de la Memoria Histórica Nayibe Sánchez Enfoque de Personas Mayores Este proyecto se desarrolló con el apoyo técnico y financiero del Centro Nacional de Memoria Histórica (CNMH) en el marco del Convenio No. 471 de 2015 y contó con el apoyo de HelpAge International. Las opiniones y conceptos que aquí se expresan son de los autores y personajes y no reflejan necesariamente la posición ni las opiniones de sus editores, del CNMH o de HelpAge Internacional. OJALÁ NOS ALCANCE LA VIDA HISTORIAS DE VIDA DE PERSONAS MAYORES VÍCTIMAS DEL CONFLICTO ARMADO COLOMBIANO ISBN: 978-958-8944-69-2 Primera edición: agosto de 2017 Número de páginas: 300 Formato: 15 x 23 cm Coordinación Grupo de Comunicaciones: Adriana Correa Mazuera Coordinación editorial: Tatiana Peláez Acevedo Edición y corrección de

[Abstract] The neural substrates of fatigue induced by muscular activity have been addressed in depth in relation to isometric tasks. For these activities, when fatigue develops, it has been noted that the duration of the silent periods (SPs) increases in response to both transcranial magnetic stimulation (TMS) of primary motor cortex or electric cervicomedullary stimulation (CMS). However, fatigue is known to be task-dependent and the mechanisms giving rise to a decrease in motor performance during brief, fast repetitive tasks have been less studied. We hypothesized that fatigue induced by repetitive fast finger tapping may have physiological mechanisms different from those accounting for fatigue during an isometric contraction, even in cases of matched effort durations. In these tasks, we examined the contribution of spinal and supraspinal motor circuits to the production of fatigue. The tapping rate and maximal voluntary contractions (MVC), and TMS- and CMS-evoked SPs were obtained at the time of fatigue, and while subjects maintained maximal muscle activation after fast finger-tapping (or isometric activity) of different durations (10 or 30 s). Results showed different mechanisms of fatigue triggered by isometric contraction and repetitive movements, even of short duration. Short-lasting repetitive movements induce fatigue within intracortical inhibitory circuits. They increased TMS-SPs, but not CMS-SPs. On the other hand, isometric contraction had a clear impact on spinal circuits. The consideration of these differences might help to optimize the study of fatigue in physiological conditions and neurological disorders.

[Abstract] A new cross-correlation synchrony index for neural activity is proposed. The index is based on the integration of the kernel estimation of the cross-correlation function. It is used to test for the dynamic synchronization levels of spontaneous neural activity under two induced brain states: sleep-like and awake-like. Two bootstrap resampling plans are proposed to approximate the distribution of the test statistics. The results of the first bootstrap method indicate that it is useful to discern significant differences in the synchronization dynamics of brain states characterized by a neural activity with low firing rate. The second bootstrap method is useful to unveil subtle differences in the synchronization levels of the awake-like state, depending on the activation pathway.

[Abstract] The corticospinal tract excitability is modulated when preparing movements. Earlier to movement execution, the excitability of the spinal cord increases waiting for supraspinal commands to release the movement. Movement execution and movement observation share processes within the motor system, although movement observation research has focused on processes later to movement onset. We used single and paired pulse transcranial magnetic stimulation on M1 (n = 12), and electrical cervicomedullary stimulation (n = 7), to understand the modulation of the corticospinal system during the “preparation” to observe a third person's movement. Subjects passively observed a hand that would remain still or make an index finger extension. The observer's corticospinal excitability rose when “expecting to see a movement” vs. when “expecting to see a still hand.” The modulation took origin at a spinal level and not at the corticocortical networks explored. We conclude that expectancy of seeing movements increases the excitability of the spinal cord.

[Abstract] A new synchrony index for neural activity is de ned in this paper. The method is able to measure synchrony dynamics in low ring rate scenarios. It is based on the computation of the time intervals between nearest spikes of two given spike trains. Generalized additive models are proposed for the synchrony pro les obtained by this method. Two hypothesis tests are proposed to assess for di erences in the level of synchronization in a real data example. Bootstrap methods are used to calibrate the distribution of the tests. Also, the expected synchrony due to chance is computed analytically and by simulation to assess for actual synchronization.

[Abstract] Background: Pairwise association between neurons is a key feature in understanding neural coding. Statistical neuroscience provides tools to estimate and assess these associations. In the mammalian brain, activating ascending pathways arise from neuronal nuclei located at the brainstem and at the basal forebrain that regulate the transition between sleep and awake neuronal firing modes in extensive regions of the cerebral cortex, including the primary visual cortex, where neurons are known to be selective for the orientation of a given stimulus. In this paper, the estimation of neural synchrony as a function of time is studied in data obtained from anesthetized cats. A functional data analysis of variance model is proposed. Bootstrap statistical tests are introduced in this context; they are useful tools for the study of differences in synchrony strength regarding 1) transition between different states (anesthesia and awake), and 2) affinity given by orientation selectivity. Results: An analysis of variance model for functional data is proposed for neural synchrony curves, estimated with a cross-correlation based method. Dependence arising from the experimental setting needs to be accounted for. Bootstrap tests allow the identification of differences between experimental conditions (modes of activity) and between pairs of neurons formed by cells with different affinities given by their preferred orientations. In our test case, interactions between experimental conditions and preferred orientations are not statistically significant. Conclusions: The results reflect the effect of different experimental conditions, as well as the affinity regarding orientation selectivity in neural synchrony and, therefore, in neural coding. A cross-correlation based method is proposed that works well under low firing activity. Functional data statistical tools produce results that are useful in this context. Dependence is shown to be necessary to account for, and bootstrap

[Abstract] Although observation of a movement increases the excitability of the motor system of the observer, it does not induce a motor replica. What is the mechanism for replica suppression? We performed a series of experiments, involving a total of 66 healthy humans, to explore the excitability of different M1 circuits and the spinal cord during observation of simple movements. Several strategies were used. In the first and second experimental blocks, we used several delay times from movement onset to evaluate the time-course modulation of the cortico-spinal excitability (CSE), and its potential dependency on the duration of the movement observed; in order to do this single pulse transcranial magnetic stimulation (TMS) over M1 was used. In subsequent experiments, at selected delay times from movement-onset, we probed the excitability of the cortico-spinal circuits using three different approaches: (i) electric cervicomedullary stimulation (CMS), to test spinal excitability, (ii) paired-pulse TMS over M1, to evaluate the cortical inhibitory-excitatory balance (short intracortical inhibition (SICI) and intracortical facilitation (ICF)], and (iii) continuous theta-burst stimulation (cTBS), to modulate the excitability of M1 cortical circuits. We observed a stereotyped response in the modulation of CSE. At 500 ms after movement-onset the ICF was increased; although the most clear-cut effect was a decrease of CSE. The compensatory mechanism was not explained by changes in SICI, but by M1-intracortical circuits targeted by cTBS. Meanwhile, the spinal cord maintained the elevated level of excitability induced when expecting to observe movements, potentially useful to facilitate any required response to the movement observed.

Este artículo aspira analizar teóricamente el carácter de la relación entre cultura y política. Para ello se hace referencia al debate teórico en torno al significado de los conceptos Cultura y culturas; y se formulan las siguientes interrogantes ¿Es complementaria o antagónica la relación entre cultura y política? ¿Practican los pueblos la política que imaginan? Para cuyas respuestas se hace uso de la propuesta filosófica elaborada por Michael Oakeshott y la modalidad de la teoría del discurso desarrollada por Ernesto Laclau. A partir de estas consideraciones teóricas se intenta formular un esquema interpretativo de la construcción discusiva de la realidad política venezolana en cuatro momentos históricos: la ruptura del nexo colonial, los regímenes oligárquico-liberales, la “adequidad” y el “chavecismo”.

El tema de la crisis se ha impuesto con fuerza tópica en nuestra cotidianidad política. Se supone que ésta es producto de la exacerbación de las demandas sociales sobre las instituciones gubernamentales, cuya sobrecarga genera una situación de ingobernabilidad. Preocupa que los diagnósticos que se hacen sobre el particular tiendan a obliterar la dimensión simbólica que interviene en la formación de la identidad de los actores colectivos. Postulamos que la crisis que confronta la sociedad venezolana debe ser analizada además, en términos de los desplazamientos y reacomodos a que han sido sometidos sus dispositivos simbólicos. Esta vertiente de análisis, de inspiración antropológica, privilegia la dimensión discursiva e intenta despejar pistas que faciliten la indagación sobre la constitución de nuestra modernidad política y cultural.

Se analiza la relación entre dos dimensiones civilizacionales: formas culturales y expresión política. Se hace referencia a los aportes que sobre esta problemática ha proporcionado la sociología clásica, en particular Durkheim y Weber. Igualmente se revisan los formulados por la teoría de la transición (Gino Germani, Torcuato Di Tella) y los contenidos en el libro editado por Lawrence Harrison y Samuel Huntington, “Culture Maters. How Values Shape Human Progress”. Se presta especial atención al concepto de capital social. Asimismo se discute la relación entre universalismo y particularismo en términos del debate teórico presente en la filosofía política contemporánea y se formula una hipótesis explicativa sobre la situación política actual que enfrenta Venezuela.

Las sociedades latinoamericanas han experimentado históricamente dificultades para construir una cultura política verdaderamente democrática. A manera de hipótesis proponemos que estas dificultades de circunstancia son producto de la disociación que tradicionalmente ha existido entre lengua y palabra. A partir de los aportes de la lingüística estructural y el psicoanálisis lacaniano se formula una diferenciación entre lenguaje público y habla popular; y se propone que la articulación entre ambas dimensiones debe darse en el marco de un intenso proceso de hibridación cultural que facilite la apertura hacia el otro sin menoscabo de lo propio. Se concluye que la verdadera radicalidad democrática en América Latina debe buscarse a través de la construcción de una cultura política que promueva el mestizaje entre las diversas identidades culturales: la homogeneidad nunca ha sido democrática.

[Abstract] Increased antagonist muscle co-activation of the lower limb during walking seems to be an adaptive process to the physiological changes of aging, in order to gain joint stability. In the healthy subjects this view seems to be reinforced by the fact that the co-activation index (CAI) increases when the gait is faster. The few reports on antagonist co-activation in Parkinson's disease (PD) patients indicate that they have larger co-activation than the healthy elderly, supporting the idea of the stabilization role of CAI during gait, as postural instability is a cardinal feature of PD. However it has also been reported that there is a reduction of the CAI when increasing velocity in PD or normal elderly. This questions the role of coactivation in stabilization during increased velocity. In this study we have analyzed the gait of healthy subjects (young and elderly), and PD patients (with and without freezing of gait, FOG) in order to better understand the relation between co-activation and gait kinematics, and to gain insight into the pathological changes associated with FOG in PD. We used Multiple Linear Regression models to study the relationship in shank muscles between CAI, velocity and cadence. Our results indicate that, for all groups of interest, the relationship between co-activation and the kinematics of gait is poor, due to the high degree of variability, questioning the explanatory value of the index.

[Abstract] The transient visual response of feline dorsal lateral geniculate nucleus (dLGN) cells was studied under control conditions and during the application of repetitive transcranial magnetic stimulation at 1 Hz (rTMS@1Hz) on the primary visual cortex (V1). The results show that rTMS@1Hz modulates the firing mode of Y cells, inducing an increase in burst spikes and a decrease in tonic firing. On the other hand, rTMS@1Hz modifies the spatiotemporal characteristics of receptive fields of X cells, inducing a delay and a decrease of the peak response, and a change of the surround/center amplitude ratio of RF profiles. These results indicate that V1 controls the activity of the visual thalamus in a different way in the X and Y pathways, and that this feedback control is consistent with functional roles associated with each cell type.

[Abstract] Understanding the link between neuronal responses (NRs) and metabolic signals is fundamental to our knowledge of brain function and it is a milestone in our efforts to interpret data from modern non invasive optical techniques such as fMRI, which are based on the close coupling between metabolic demand of active neurons and local changes in blood flow. The challenge is to unravel the link. Here we show, using spectrophotometry to record oxyhaemoglobin and methemoglobin (surrogate markers of cerebral flow and nitric oxide levels respectively) together with extracellular neuronal recordings in vivo and applying a multiple polynomial regression model, that the markers are able to predict up about 80% of variability in NR. Furthermore, we show that the coupling between blood flow and neuronal activity is heavily influenced by nitric oxide (NO). While NRs show the typical saturating response, blood flow shows a linear behaviour during contrast-response curves, with nitric oxide from different sources acting differently for low and high intensity.