52 research outputs found
On the Relation between Bursts and Dynamic Synapse Properties: a Modulation-Based Ansatz
When entering a synapse, presynaptic pulse trains are filtered according to the recent pulse history at the synapse and also with respect to their own pulse time course. Various behavioral models have tried to reproduce these complex filtering properties. In particular, the quantal model of neurotransmitter release has been shown to be highly
selective for particular presynaptic pulse patterns. However, since the original, pulse-iterative quantal model does not lend itself to mathematical analysis, investigations have only been carried out via simulations. In contrast, we derive a comprehensive explicit expression for the quantal model. We show the correlation between the parameters of this explicit
expression and the preferred spike train pattern of the synapse. In particular, our analysis of the transmission of modulated pulse trains across a dynamic synapse links the original parameters of the quantal model to the transmission efficacy of two major spiking regimes, that is, bursting and constant-rate ones
Birthplace diversity of the workforce and productivity spill-overs in firms
We analyze the effect of workforce composition by birthplace on workers' wages. In our model, each worker's productivity may depend on whether co-workers are of the same or of a different birthplace. Wages depend both on the relative size of workers' groups as well as on the production structure of firms. We derive empirically testable hypotheses about the effect of co-worker birthplace on wages using a stylized model of intra-firm spill-overs across worker groups. We find evidence for complementarities between workers of different birthplace in line with our model
Immersive Imagination in Urban Oases of Mindfulness: The VR-SenseCity Toolbox for Sensible, Emotional and Measurable Experiences in Future Smart Cities
Quality of life, health and well-being, as well as the creative potential originating from positive experiences and interaction with our environment and interaction are pivotal human factors underlying a rich and productive social context. Respect and careful treatment of users, i.e., the citizen who will populate, co-create and co-operate in the scenarios, mandate overarching topics for developing user centered designschematas. Virtual Reality (VR) technologies have recently offered tools to anticipate the affordances of future scenarios. In the serious game VR-SenseCity (Paletta et al., 2017) we created tools for the imagination of affective and sensory experiences, in particular, referring to visual affordances that enable induction of imaginated sensory experiences in real urban environments. We investigated the potential for the motivation of elderly people, in particular, persons with dementia, to encounter their daily environment in positive attitude, with pleasant and aware sensory experiences, the purpose to improve their cognitive reserve (Stern, 2009). The functionalities were developed in cooperation with a Co-creation group of four elderly persons providing substantial critical and constructive feedback for the development of the toolbox
VLSI Implementation of a 2.8 Gevent/s Packet-Based AER Interface with Routing and Event Sorting Functionality
State-of-the-art large-scale neuromorphic systems require sophisticated spike event communication between units of the neural network. We present a high-speed communication infrastructure for a waferscale neuromorphic system, based on application-specific neuromorphic communication ICs in an field programmable gate arrays (FPGA)-maintained environment. The ICs implement configurable axonal delays, as required for certain types of dynamic processing or for emulating spike-based learning among distant cortical areas. Measurements are presented which show the efficacy of these delays in influencing behavior of neuromorphic benchmarks. The specialized, dedicated address-event-representation communication in most current systems requires separate, low-bandwidth configuration channels. In contrast, the configuration of the waferscale neuromorphic system is also handled by the digital packet-based pulse channel, which transmits configuration data at the full bandwidth otherwise used for pulse transmission. The overall so-called pulse communication subgroup (ICs and FPGA) delivers a factor 25–50 more event transmission rate than other current neuromorphic communication infrastructures
Neuromorphic Hardware In The Loop: Training a Deep Spiking Network on the BrainScaleS Wafer-Scale System
Emulating spiking neural networks on analog neuromorphic hardware offers
several advantages over simulating them on conventional computers, particularly
in terms of speed and energy consumption. However, this usually comes at the
cost of reduced control over the dynamics of the emulated networks. In this
paper, we demonstrate how iterative training of a hardware-emulated network can
compensate for anomalies induced by the analog substrate. We first convert a
deep neural network trained in software to a spiking network on the BrainScaleS
wafer-scale neuromorphic system, thereby enabling an acceleration factor of 10
000 compared to the biological time domain. This mapping is followed by the
in-the-loop training, where in each training step, the network activity is
first recorded in hardware and then used to compute the parameter updates in
software via backpropagation. An essential finding is that the parameter
updates do not have to be precise, but only need to approximately follow the
correct gradient, which simplifies the computation of updates. Using this
approach, after only several tens of iterations, the spiking network shows an
accuracy close to the ideal software-emulated prototype. The presented
techniques show that deep spiking networks emulated on analog neuromorphic
devices can attain good computational performance despite the inherent
variations of the analog substrate.Comment: 8 pages, 10 figures, submitted to IJCNN 201
Low aerobic mitochondrial energy metabolism in poorly- or undifferentiated neuroblastoma
<p>Abstract</p> <p>Background</p> <p>Succinate dehydrogenase (SDH) has been associated with carcinogenesis in pheochromocytoma and paraganglioma. In the present study we investigated components of the oxidative phosphorylation system in human neuroblastoma tissue samples.</p> <p>Methods</p> <p>Spectrophotometric measurements, immunohistochemical analysis and Western blot analysis were used to characterize the aerobic mitochondrial energy metabolism in neuroblastomas (NB).</p> <p>Results</p> <p>Compared to mitochondrial citrate synthase, SDH activity was severely reduced in NB (n = 14) versus kidney tissue. However no pathogenic mutations could be identified in any of the four subunits of SDH. Furthermore, no genetic alterations could be identified in the two novel SDH assembly factors SDHAF1 and SDH5. Alterations in genes encoding nfs-1, frataxin and isd-11 that could lead to a diminished SDH activity have not been detected in NB.</p> <p>Conclusion</p> <p>Because downregulation of other complexes of the oxidative phosphorylation system was also observed, a more generalized reduction of mitochondrial respiration seems to be present in neuroblastoma in contrast to the single enzyme defect found in hereditary pheochromocytomas.</p
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