Inference of Spiking Activity Origin in Developing Cortical Networks on Planar Multi-electrode Arrays using Genetically Encoded Calcium Indicators
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1
Universitätsmedizin Mainz, Institute of Physiology, Germany
From their introduction on, multi-electrode arrays (MEAs) have paved the way for the analysis of large neuronal ensembles, enabling neural circuitry topology and functions to be explored. Although the recording capability of MEAs increased significantly, the processing capability of the resulting large data sets has lagged behind, in particular keeping a critical issue: the proper link between electrical signals and the respective neurons. At the current state of the art, recorded action potentials waveforms are sorted according to their shapes into putative units but cannot be traced back to the biological neurons. In addition, only spikes originating from few active cells near to the electrodes contribute to the processed signal. In contrast, spikes from adjacent neurons with a low signal-to-noise ratio, as well as spikes from sparsely firing neurons are not taken in consideration. Thus, besides the intrinsic physical constraints of MEAs that preclude an exhaustive analysis of every neuron within the examined sample, also the sorting inaccuracy affects refined data acquisition performance, eventually resulting in a large loss of information.
Here, we show that the combination of MEA technology with calcium imaging offers the advantage of complementing the high temporal resolution of electrical recordings with the accurate optical identification of calcium dynamics, in order to reliably and unbiasedly reconstruct single cell and network firing behavior. In our model, dissociated cortical neurons cultured on in vitro MEAs are transduced with a recombinant adeno associated virus vector carrying two transgenes, a fluorescent nuclear marker nls-dTomato and the calcium indicator GCaMP6s. The nuclear marker reveals the exact localization of each active and silent neuron, while the calcium indicator enables single cell calcium transient detection. By matching spiking activity from the obtained calcium traces with the corresponding processed electrical signals, we are then able to unequivocally associate the identified units to specific biological neurons. Using the derived firing signature as a benchmark, we can advisedly decipher the calcium traces from the electrically missed neurons and, taking into account also silent cells, reconstruct the complete anatomo-functional neuronal network. Thus, the combined approach of optical imaging and MEA recordings allows us to investigate how single neurons integrate and participate in immature neuronal networks and might ultimately resolve how early activity patterns predict neuronal integration and contribution in mature network activity.
Acknowledgements
This work was supported by funding from the DFG to H.J.L. and A.S. (CRC 1080), and intra-mural research funding to A.S. (Stufe 1). AAV-hSyn1-GCaMP6s-P2A-nls-dTomato was a gift from Jonathan Ting (Addgene plasmid # 51084).
Keywords:
multi-electrode-array,
primary neuronal culture,
calcium imaging,
GCaMP6,
developing neuronal networks
Conference:
MEA Meeting 2018 | 11th International Meeting on Substrate Integrated Microelectrode Arrays, Reutlingen, Germany, 4 Jul - 6 Jul, 2018.
Presentation Type:
Oral Presentation
Topic:
Neural Networks
Citation:
Warm
D,
Wong Fong Sang
IE,
Kilb
W,
Luhmann
HJ and
Sinning
A
(2019). Inference of Spiking Activity Origin in Developing Cortical Networks on Planar Multi-electrode Arrays using Genetically Encoded Calcium Indicators.
Conference Abstract:
MEA Meeting 2018 | 11th International Meeting on Substrate Integrated Microelectrode Arrays.
doi: 10.3389/conf.fncel.2018.38.00119
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Received:
15 Mar 2018;
Published Online:
17 Jan 2019.
*
Correspondence:
Prof. Heiko J Luhmann, Universitätsmedizin Mainz, Institute of Physiology, Mainz, 55128, Germany, luhmann@uni-mainz.de
Dr. Anne Sinning, Universitätsmedizin Mainz, Institute of Physiology, Mainz, 55128, Germany, asinning@uni-mainz.de