Neural ensemble communities: open-source approaches to hardware for large-scale electrophysiology

Abstract

One often-overlooked factor when selecting a platform for large-scale electrophysiology is whether or not a particular data acquisition system is 'open' or 'closed': that is, whether or not the system's schematics and source code are available to end users. Open systems have a reputation for being difficult to acquire, poorly documented, and hard to maintain. With the arrival of more powerful and compact integrated circuits, rapid prototyping services, and web-based tools for collaborative development, these stereotypes must be reconsidered. We discuss some of the reasons why multichannel extracellular electrophysiology could benefit from open-source approaches and describe examples of successful community-driven tool development within this field. In order to promote the adoption of open-source hardware and to reduce the need for redundant development efforts, we advocate a move toward standardized interfaces that connect each element of the data processing pipeline. This will give researchers the flexibility to modify their tools when necessary, while allowing them to continue to benefit from the high-quality products and expertise provided by commercial vendors.

Figure 1. Timeline of open-source multichannel electrophysiology development

The improvements in usability, flexibility, and computational power of open-source multichannel data acquisition systems for electrophysiology have paralleled growth in open-source culture (e.g. the introduction of Arduino, Git, and YouTube in 2005) and technological developments within neuroscience (e.g. the introduction of Intan Technologies integrated bioamplifiers in 2009). In the last 20 years, the cost per acquisition channel has decreased by nearly 2 orders of magnitude while available channel counts have increased by approximately 1 order of magnitude. Standardization of hardware and software interfaces has allowed independent open-source hardware development projects to target common visualization software. For instance, the Open Ephys FPGA–based acquisition board and the ARM processor–based “Puggle” (http://www.puggleboard.com) both target the Open Ephys GUI.

Figure 2. Key interfaces within multichannel electrophysiology platforms

Overview of the main components and interfaces in multichannel electrophysiology systems. Some components and interfaces need to be incompatible in order to comply with different requirements, such as electrodes and their connectors. Others, such as interfaces for software plug-ins or the interfaces between recording hardware and software, could be standardized with little additional development cost.