Synaptic plasticity in spiking neural networks (SP(2)INN): a system approach.

In this paper, we present a digital system called (SP/sup 2/INN) for simulating very large-scale spiking neural networks (VLSNNs) comprising, e.g., 1000000 neurons with several million connections in total. SP/sup 2/INN makes it possible to simulate VLSNN with features such as synaptic short term plasticity, long term plasticity as well as configurable connections. For such VLSNN the computation of the connectivity including the synapses is the main challenging task besides computing the neuron model. We describe the configurable neuron model of SP/sup 2/INN, before we focus on the computation of the connectivity. Within SP/sup 2/INN, connectivity parameters are stored in an external memory, while the actual connections are computed online based on defined connectivity rules. The communication between the SP/sup 2/INN processor and the external memory represents a bottle-neck for the system performance. We show this problem is handled efficiently by introducing a tag scheme and a target-oriented addressing method. The SP/sup 2/INN processor is described in a high-level hardware description language. We present its implementation in a 0.35 /spl mu/m CMOS technology, but also discuss advantages and drawbacks of implementing it on a field programmable gate array.

NeuroPipe-Chip: A digital neuro-processor for spiking neural networks.

Computing complex spiking artificial neural networks (SANNs) on conventional hardware platforms is far from reaching real-time requirements. Therefore we propose a neuro-processor, called NeuroPipe-Chip, as part of an accelerator board. In this paper, we introduce two new concepts on chip-level to speed up the computation of SANNs. These concepts are implemented in a prototype of the NeuroPipe-Chip. We present the hardware structure of the prototype and evaluate its performance in a system simulation based on a hardware description language (HDL). For the computation of a simple SANN for image segmentation, the NeuroPipe-Chip operating at 100 MHz shows an improvement of more than two orders of magnitude compared to an Alpha 500 MHz workstation and approaches real-time requirements for the computation of SANNs in the order of 10(6) neurons. Hence, such an accelerator would allow for applications of complex SANNs to solve real-world tasks like real-time image processing. The NeuroPipe-Chip has been fabricated in an Alcatel 0.35-mum digital CMOS technology.