Neurogenesis Deep Learning

Neural machine learning methods, such as deep neural networks (DNN), have achieved remarkable success in a number of complex data processing tasks. These methods have arguably had their strongest impact on tasks such as image and audio processing - data processing domains in which humans have long held clear advantages over conventional algorithms. In contrast to biological neural systems, which are capable of learning continuously, deep artificial networks have a limited ability for incorporating new information in an already trained network. As a result, methods for continuous learning are potentially highly impactful in enabling the application of deep networks to dynamic data sets. Here, inspired by the process of adult neurogenesis in the hippocampus, we explore the potential for adding new neurons to deep layers of artificial neural networks in order to facilitate their acquisition of novel information while preserving previously trained data representations. Our results on the MNIST handwritten digit dataset and the NIST SD 19 dataset, which includes lower and upper case letters and digits, demonstrate that neurogenesis is well suited for addressing the stability-plasticity dilemma that has long challenged adaptive machine learning algorithms.Comment: 8 pages, 8 figures, Accepted to 2017 International Joint Conference on Neural Networks (IJCNN 2017

Magnetic Tunnel Junction Random Number Generators Applied to Dynamically Tuned Probability Trees Driven by Spin Orbit Torque

Perpendicular magnetic tunnel junction (pMTJ)-based true-random number generators (RNG) can consume orders of magnitude less energy per bit than CMOS pseudo-RNG. Here, we numerically investigate with a macrospin Landau-Lifshitz-Gilbert equation solver the use of pMTJs driven by spin-orbit torque to directly sample numbers from arbitrary probability distributions with the help of a tunable probability tree. The tree operates by dynamically biasing sequences of pMTJ relaxation events, called 'coinflips', via an additional applied spin-transfer-torque current. Specifically, using a single, ideal pMTJ device we successfully draw integer samples on the interval 0,255 from an exponential distribution based on p-value distribution analysis. In order to investigate device-to-device variations, the thermal stability of the pMTJs are varied based on manufactured device data. It is found that while repeatedly using a varied device inhibits ability to recover the probability distribution, the device variations average out when considering the entire set of devices as a 'bucket' to agnostically draw random numbers from. Further, it is noted that the device variations most significantly impact the highest level of the probability tree, iwth diminishing errors at lower levels. The devices are then used to draw both uniformly and exponentially distributed numbers for the Monte Carlo computation of a problem from particle transport, showing excellent data fit with the analytical solution. Finally, the devices are benchmarked against CMOS and memristor RNG, showing faster bit generation and significantly lower energy use.Comment: 10 pages, 8 figures, 2 table

Beneficial Betrayal Aversion

Many studies demonstrate the social benefits of cooperation. Likewise, recent studies convincingly demonstrate that betrayal aversion hinders trust and discourages cooperation. In this respect, betrayal aversion is unlike socially “beneficial” preferences including altruism, fairness and inequity aversion, all of which encourage cooperation and exchange. To our knowledge, other than the suggestion that it acts as a barrier to rash trust decisions, the benefits of betrayal aversion remain largely unexplored. Here we use laboratory experiments with human participants to show that groups including betrayal-averse agents achieve higher levels of reciprocity and more profitable social exchange than groups lacking betrayal aversion. These results are the first rigorous evidence on the benefits of betrayal aversion, and may help future research investigating cultural differences in betrayal aversion as well as future research on the evolutionary roots of betrayal aversion. Further, our results extend the understanding of how intentions affect social interactions and exchange and provide an effective platform for further research on betrayal aversion and its effects on human behavior

The Role of Additive Neurogenesis and Synaptic Plasticity in a Hippocampal Memory Model with Grid-Cell Like Input

Recently, we presented a study of adult neurogenesis in a simplified hippocampal memory model. The network was required to encode and decode memory patterns despite changing input statistics. We showed that additive neurogenesis was a more effective adaptation strategy compared to neuronal turnover and conventional synaptic plasticity as it allowed the network to respond to changes in the input statistics while preserving representations of earlier environments. Here we extend our model to include realistic, spatially driven input firing patterns in the form of grid cells in the entorhinal cortex. We compare network performance across a sequence of spatial environments using three distinct adaptation strategies: conventional synaptic plasticity, where the network is of fixed size but the connectivity is plastic; neuronal turnover, where the network is of fixed size but units in the network may die and be replaced; and additive neurogenesis, where the network starts out with fewer initial units but grows over time. We confirm that additive neurogenesis is a superior adaptation strategy when using realistic, spatially structured input patterns. We then show that a more biologically plausible neurogenesis rule that incorporates cell death and enhanced plasticity of new granule cells has an overall performance significantly better than any one of the three individual strategies operating alone. This adaptation rule can be tailored to maximise performance of the network when operating as either a short- or long-term memory store. We also examine the time course of adult neurogenesis over the lifetime of an animal raised under different hypothetical rearing conditions. These growth profiles have several distinct features that form a theoretical prediction that could be tested experimentally. Finally, we show that place cells can emerge and refine in a realistic manner in our model as a direct result of the sparsification performed by the dentate gyrus layer

Ingeniería de tejidos: estudio de hemograma de conejos New Zealand con lesion femoral post-implante de matriz de tercera generaci{on con potencialidad osteoregenerativa

La alta tasa de fracturas a nivel mundial, ha promovido el desarrollo de matrices con la intención de ser aplicados como implantes frente a lesiones óseas, intentado promover la regeneración tisular de novo. En el laboratorio se han comenzado a desarrollar investigaciones tendientes a considerar como potenciales matrices a los recombinámeros de tipo elastina, matrices de tercera generación obtenidas por estrategias de biología molecular (ELRs de las palabras en ingles elastin-like recombinamers, que significan recombinàmeros del tipo elastina).. La propia composición de los ELRs, basada en la repetición de la elastina natural, le dota al material de una serie de propiedades que son difícilmente encontrables en otras familias de polímeros: autoensamblado y adecuadas propiedades mecánicas de sus hidrogeles, asì como la sencilla manipulación frente a su implante, ya que son líquidos en estado refrigerado y gelifican a Ta ambiente o mayor, es decir son de gelificación inversa. Hemos desarrollado previamente un modelo de lesión ósea en fémur de conejo,. Este proyecto pretende frente a este modelo y el implante de ELRs, investigar si se ven afectados o no los hemogramas de los conejos implantados, aportando resultados de lo que ocurre in vivo, contribuyendo a la caracterización de esta estrategia de ingeniería de tejidos. Modelo experimental: Conejos hembras de la línea New Zealand de tres meses de edad, .se dividieron en tres grupos I, II y III ( n= 5 c/u) . Los grupos I y II recibieron bajo anestesia lesión distal-medial del fémur de 6 mm diámetro todo bajo estrictas normas de anestesia y tratamiento del dolor, Sin embargo los animales del grupo I recibieron a su vez a posteriori de este proceso el implante de Elrs, mientras que los animales del grupo II no lo recibieron; III fue grupo control. En tiempos preimplante y a los tres meses, previo al sacrificio de los animales para la realización de otros estudios en paralelo, se extrajeron muestras de sangre en tubos heparinizados para la realización de hemogramas, previa homogenización de las muestras. Se realizaron recuento de Glóbulos rojos (GR), Glóbulos blancos (GB), Hemoglobina (Hb), Hematocrito (Hto), Volumen corpuscular medio(MCV), plaquetas. No se observaron diferencias significativas para las variables mencionadas al realizar los estudios estadísticos mediante programa computadorizado infostat UNC, tanto a nivel intergrupal (test de Kruskall wallis), ni al comparar los estados iniciales y finales del experimento para cada grupo (test de Wicolxon). Dado lo novedoso de este tipo de matrices, consideramos que este tipo de estudios aportan datos imprescindibles para realizar caracterizaciones de los procesos in vivo post-implante, y sumados a otras caracterizaciones bioquímicas, clínicas y anatomopatológicas que estamos realizando, permitirán quizás a futuro considerar potenciales estudios pre-clínicos.Fil: Garbino, Federico. Universidad Nacional de Rosario. Facultad de Ciencias Médicas. Laboratorio de Biología Osteoarticular, Ingeniería Tisular y Terapias Emergentes; ArgentinaFil: Coletta, Dante Jesus. Universidad Nacional de Rosario. Facultad de Ciencias Médicas. Laboratorio de Biología Osteoarticular, Ingeniería Tisular y Terapias Emergentes; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Médicas. Laboratorio de Biología Osteoarticular, Ingeniería Tisular y Terapias Emergentes; ArgentinaFil: Ibañez Fonseca, Arturo. No especifíca;Fil: Radice, Maria Beatriz. Universidad Nacional de Rosario. Facultad de Ciencias Médicas. Laboratorio de Biología Osteoarticular, Ingeniería Tisular y Terapias Emergentes; ArgentinaFil: Aimone, Maria Angeles. Universidad Nacional de Rosario. Facultad de Ciencias Médicas. Laboratorio de Biología Osteoarticular, Ingeniería Tisular y Terapias Emergentes; ArgentinaFil: Missana, Liliana Raquel. Universidad Nacional de Tucumán. Facultad de Odontología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Alonso, Matilde. Universidad de Valladolid; EspañaFil: Rodriguez Cabello, J. C.. Universidad de Valladolid; EspañaFil: Feldman, Sara. Universidad Nacional de Rosario. Facultad de Ciencias Médicas. Laboratorio de Biología Osteoarticular, Ingeniería Tisular y Terapias Emergentes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaXVIII Congreso y XXXVI Reunión Anual de la Sociedad de Biología de RosarioRosarioArgentinaSociedad de Biología de RosarioUniversidad Nacional de Rosari

Cellular and Behavioral Effects of Cranial Irradiation of the Subventricular Zone in Adult Mice

Background: In mammals, new neurons are added to the olfactory bulb (OB) throughout life. Most of these new neurons, granule and periglomerular cells originate from the subventricular zone (SVZ) lining the lateral ventricles and migrate via the rostral migratory stream toward the OB. Thousands of new neurons appear each day, but the function of this ongoing neurogenesis remains unclear. Methodology/Principal Findings: In this study, we irradiated adult mice to impair constitutive OB neurogenesis, and explored the functional impacts of this irradiation on the sense of smell. We found that focal irradiation of the SVZ greatly decreased the rate of production of new OB neurons, leaving other brain areas intact. This effect persisted for up to seven months after exposure to 15 Gray. Despite this robust impairment, the thresholds for detecting pure odorant molecules and short-term olfactory memory were not affected by irradiation. Similarly, the ability to distinguish between odorant molecules and the odorant-guided social behavior of irradiated mice were not affected by the decrease in the number of new neurons. Only long-term olfactory memory was found to be sensitive to SVZ irradiation. Conclusion/Significance: These findings suggest that the continuous production of adult-generated neurons is involved i

Learning to Learn: Theta Oscillations Predict New Learning, which Enhances Related Learning and Neurogenesis

Animals in the natural world continuously encounter learning experiences of varying degrees of novelty. New neurons in the hippocampus are especially responsive to learning associations between novel events and more cells survive if a novel and challenging task is learned. One might wonder whether new neurons would be rescued from death upon each new learning experience or whether there is an internal control system that limits the number of cells that are retained as a function of learning. In this experiment, it was hypothesized that learning a task that was similar in content to one already learned previously would not increase cell survival. We further hypothesized that in situations in which the cells are rescued hippocampal theta oscillations (3–12 Hz) would be involved and perhaps necessary for increasing cell survival. Both hypotheses were disproved. Adult male Sprague-Dawley rats were trained on two similar hippocampus-dependent tasks, trace and very-long delay eyeblink conditioning, while recording hippocampal local-field potentials. Cells that were generated after training on the first task were labeled with bromodeoxyuridine and quantified after training on both tasks had ceased. Spontaneous theta activity predicted performance on the first task and the conditioned stimulus induced a theta-band response early in learning the first task. As expected, performance on the first task correlated with performance on the second task. However, theta activity did not increase during training on the second task, even though more cells were present in animals that had learned. Therefore, as long as learning occurs, relatively small changes in the environment are sufficient to increase the number of surviving neurons in the adult hippocampus and they can do so in the absence of an increase in theta activity. In conclusion, these data argue against an upper limit on the number of neurons that can be rescued from death by learning

Continued Neurogenesis in Adult Drosophila as a Mechanism for Recruiting Environmental Cue-Dependent Variants

Background The skills used by winged insects to explore their environment are strongly dependent upon the integration of neurosensory information comprising visual, acoustic and olfactory signals. The neuronal architecture of the wing contains a vast array of different sensors which might convey information to the brain in order to guide the trajectories during flight. In Drosophila, the wing sensory cells are either chemoreceptors or mechanoreceptors and some of these sensors have as yet unknown functions. The axons of these two functionally distinct types of neurons are entangled, generating a single nerve. This simple and accessible coincidental signaling circuitry in Drosophila constitutes an excellent model system to investigate the developmental variability in relation to natural behavioral polymorphisms. Methodology/Principal Findings A fluorescent marker was generated in neurons at all stages of the Drosophila life cycle using a highly efficient and controlled genetic recombination system that can be induced in dividing precursor cells (MARCM system, flybase web site). It allows fluorescent signals in axons only when the neuroblasts and/or neuronal cell precursors like SOP (sensory organ precursors) undergo division during the precedent steps. We first show that a robust neurogenesis continues in the wing after the adults emerge from the pupae followed by an extensive axonal growth. Arguments are presented to suggest that this wing neurogenesis in the newborn adult flies was influenced by genetic determinants such as the frequency dependent for gene and by environmental cues such as population density. Conclusions We demonstrate that the neuronal architecture in the adult Drosophila wing is unfinished when the flies emerge from their pupae. This unexpected developmental step might be crucial for generating non-heritable variants and phenotypic plasticity. This might therefore constitute an advantage in an unstable ecological system and explain much regarding the ability of Drosophila to robustly adapt to their environment