Relacs ("Relaxed ELectrophysiological data Acquisition, Control, and Stimulation") is a fully customizable software platform for data acquisition, online analysis, and stimulus generation specifically designed for electrophysiological recordings. Filters and spike detectors can be applied instantly on the recorded potentials. Freely programmable, hardware independent C++ plugins can access the preprocessed data for further online analysis and visualization. Therefore the experimental protocols can automatically adapt a stimulus (e.g. offset, variance, etc.) in a closed loop fashion and thus completely control the running experiment. For programming the experimental protocols, the Relacs package also provides a data analysis library containing algorithms for basic statistics (moments, quartiles, histogram), power spectra, coherence, transfer function, linear fits, non-linear fits (Simplex, Levenberg-Marquardt), firing rates (mean, PSTH binned/kernel, 1/ISI), CV, Fano factor, ISI correlations, vector strength, reliability, jitter, mutual information (lower and upper bound), etc. A simulation mode not only allows to test and improve the experimental protocols, but also to check the performance of models with the very same procedures that were used in the real electrophysiological experiments.
The dynamic clamp is a closed-loop experiment on a per sample basis where each sampled value of the cell's membrane potential is used to compute a current that is injected back into the cell. Relacs supports software dynamic clamp, i.e. no additional hardware is needed, that is implemented as an RTAI real time Linux kernel module. For using the full potential of discontinuous current-clamp amplifiers for the dynamic clamp we are synchronizing the switching cycle of an npi SEC amplifier with the software loop (in collaboration with H. R. Polder, npi electronic GmbH, Tamm, Germany).
Very important for enhancing the reusability of acquired data is their annotation with meta-data that specify the context of the experiment. Upon completion of a recording, Relacs immediately forces the experimenter to provide this important information through a freely configurable dialog. In addition, for each recording all configuration files, log files, and version numbers and settings of the experimental protocols are saved as well. All the meta-data can be automatically stored in LabLog (see Poster by Jan Grewe) for enhancing reusability of the recorded data.
Relacs is free and open software published under the GPL to foster development and exchange of innovative experimental protocols and analysis techniques. In particular, Relacs will be a test bed for the data analysis toolboxes and data format interfaces from the German Neuroinformatics Node (www.g-node.org). For more information and downloads visit www.relacs.net.