Abstract
Enhanced understanding and control of electrophysiology mechanisms are increasingly being hailed as key knowledge in the fields of modern biology and medicine. As more and more excitable cell mechanics are being investigated and exploited, the need for flexible electrophysiology setups becomes apparent. With that aim, we designed Multimed, which is a versatile hardware platform for the real-time recording and processing of biosignals. Digital processing in Multimed is an arrangement of generic processing units from a custom library. These can freely be rearranged to match the needs of the application. Embedded onto a Field Programmable Gate Array (FPGA), these modules utilize full-hardware signal processing to lower processing latency. It achieves constant latency, and sub-millisecond processing and decision-making on 64 channels. The FPGA core processing unit makes Multimed suitable as either a reconfigurable electrophysiology system or a prototyping platform for VLSI implantable medical devices. It is specifically designed for open- and closed-loop experiments and provides consistent feedback rules, well within biological microseconds timeframes. This paper presents the specifications and architecture of the Multimed system, then details the biosignal processing algorithms and their digital implementation. Finally, three applications utilizing Multimed in neuroscience and diabetes research are described. They demonstrate the system’s configurability, its multi-channel, real-time processing, and its feedback control capabilities.
Highlights
The growing number of technological advances in electronics and materials has enabled many innovative approaches in biology and medicine to interact with excitable cells and tissues
The democratization of electrophysiology techniques has motivated the design of many electrophysiology platforms, notably commercial products proposed by National Instruments (NI) [6], Intan [7], Multi Channel Systems (MCS) [8], or open-source alternatives [9], like Neurorighter [10]
Synapse-based stimulation is computed on a reconfigurable event processor: in order to minimize processing latency and to achieve acausal synaptic stimulation and decision making within the STDP window, critical processing is done in an Field Programmable Gate Array (FPGA)
Summary
The growing number of technological advances in electronics and materials has enabled many innovative approaches in biology and medicine to interact with excitable cells and tissues. The variety in measurement paradigms calls for multi-application electrophysiology platforms with easy-to-change configurations and algorithms, as well as real-time processing and feedback control features These platforms need to adapt to various tissues, as measured on different scales: signals may vary with either the material’s origin (human, primate, rodent, etc.), type of excitable tissue (brain, muscle, cardiac, or pancreatic cells), and the recording paradigm (in vitro, ex vivo, or in vivo) [1]. Clusters of depolarizing cells generate Local Field Potentials (LFPs) [3], a biphasic oscillation with spectral components ranging below 100 Hz. On a larger scale, micro-organs, such as the pancreatic islets, called islets of Langerhans, which are composed of many (hundreds to thousands of) excitable cells, display continuous oscillations, reflecting its syncytial behavior and constituting a biomarker of cell coupling. Adaptive information decoding is essential to take into account variations in signal and electrode properties, for chronic recordings [5]
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