This title appears in the Scientific Report :
2015
Obscured artifacts in multi-electrode recordings and their influence on correlation analysis
Obscured artifacts in multi-electrode recordings and their influence on correlation analysis
Many modern electrophysiological experiments focus on collecting an increasing amount of data by recording at high time resolution with large numbers of electrodes simultaneously. Therefore, commercial full package recording and data acquisition systems are often used, that provide the experimentali...
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Personal Name(s): | Sprenger, Julia (Corresponding Author) |
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Torre, Emiliano / Rostami, Vahid / Brochier, Thomas / Riehle, Alexa / Denker, Michael / Grün, Sonja | |
Contributing Institute: |
Computational and Systems Neuroscience; IAS-6 Computational and Systems Neuroscience; INM-6 |
Published in: | 2015 |
Imprint: |
2015
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Conference: | 11th Göttingen Meeting of the German Neuroscience Society, Göttingen (Germany), 2015-03-18 - 2015-03-21 |
Document Type: |
Poster |
Research Program: |
Optogenetische Analyse der für kognitive Fähigkeiten zuständigen präfrontal-hippokampalen Netzwerke in der Entwicklung Brain-inspired multiscale computation in neuromorphic hybrid systems The Human Brain Project Supercomputing and Modelling for the Human Brain Connectivity and Activity |
Publikationsportal JuSER |
Many modern electrophysiological experiments focus on collecting an increasing amount of data by recording at high time resolution with large numbers of electrodes simultaneously. Therefore, commercial full package recording and data acquisition systems are often used, that provide the experimentalist with a compact data set, thus hiding the complexity of the system and any intermediate pre-preprocessing steps. This amounts to increasingly convoluted data that finally enter analysis to elucidate mechanisms of neuronal processes.We investigated precise spike correlations in massively parallel cortical single-unit spike data recorded by a multi-electrode array implanted in motor cortex of awake behaving monkeys. Using higher-order correlation analysis methods we detected spurious synchrony of high order on a high time resolution (30kHz). These 'synchrofacts' occur with varying numbers of contributing spikes, including events of few synchronous spikes only. The occurrence probabilities of such highly precise events are typically higher than expected based on the firing rates, whereas an investigation with larger bin sizes of typical neuronal synchronization does not yield abundant coincidence counts. Moreover, a biological origin of synchrofacts is unlikely, as cortical neurons seem not to have the physical ability to synchronize on such a short time scale that is about 2 orders of magnitude smaller than the spike duration. Despite their high precision, many synchrofacts are yet imprecise enough to evade classification as artifacts by various algorithms applied during the built-in preprocessing of the recording and spike sorting systems. Other synchrofacts go undetected due to intrinsic incompatibilities between recording system and the spike sorting systems. Therefore, a substantial fraction of synchrofacts typically remains undetected.Next we investigated the raw electrode signals (at 30kHz sampling, wide band) that give rise to synchrofacts. When correlating sorted spikes of one electrode to the raw signals (spike triggered averages) at different electrodes we often observe a synchronized strong spike-related component across large portions of the array (up to 4 mm). We hypothesized that synchrofacts should be visible as a coherent signal deflection in the raw signal. When investigating the raw signal at the time of occurrence of each individual synchrofact, indeed some synchrofacts are found to reflect small, spike-like, coherent deflections. However, a part of the synchrofacts could not be related to such obvious coherent deviations in many channels, but were identified to relate to coherent signal fluctuations just above high pass cutoff frequency for spike extraction.We demonstrate how the observed artifacts, though small in absolute number, may have a large impact on a population correlation analysis. Therefore, we investigate possible origins of the artifacts in our recording set-up and suggest approaches for artifact removal, including correction factors for correlation analyses to account for the removal process. |