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Study of in vitro learning by neuronal ensembles through optogenetic stimulation

Michele Giugliano1* and Sebastiaan Van De Vijver1
  • 1 University of Antwerp, Biomedical Sciences, Belgium

Memories are an essential part of our personalities, yet how they are encoded and preserved in the brain is one of the questions in neuroscience that has eluded understanding for quite some time. While it is the prevailing view that strengthening of the synaptic contacts between neuronal cells and circuits forms the foundation of learning and memory, the physical representation of memories in neuronal networks has so far not been fully discovered. A likely candidate for the building block of learning and memory is the ensemble, i.e. a group of neurons that share strong synaptic connections, leading to robust co-activation. In the current study, we are interested in understanding how ensembles can arise, be maintained, modified and recalled from the intrinsic properties of neurons and their synapses. To this aim we employ a reduced system of dissociated cortical rat tissue combined with multi-electrode array technology for parallel electrophysiological recordings from different locations in the neuronal network. Instrumental to the manipulation of neurons and ensembles is a stimulation technique with fine temporal and spatial precision. Here, optogenetics provides a unique opportunity to sequentially activate neurons via light using a galvo-controlled laser system. Specifically, we employ the recently developed light-sensitive ion channel Chronos for its millisecond-scale kinetics, enabling fine temporal control of the excitatory neuronal population. Harnessing rules of synaptic plasticity, more specifically spike-timing dependent plasticity, repeated sequential activation of a group of neurons is hypothesised to directionally strengthen their synaptic contacts, leading to the formation of a novel ensemble. The principle of Hebbian plasticity, namely that co-active neurons change the efficacy of their synaptic contacts, implies that the optical stimulation by a laser moving in space across an arbitrary group of neurons would reinforce its connections, creating a novel functional group. If proven true, this would indicate that neuronal networks are intrinsically capable of 'recording' an external input. Importantly, it would provide a simplified model system of learning and memory with which to probe essential properties of these 'memories' such as spontaneous and induced replay, longevity, susceptibility to modifications and our ability to 'read-out' encoded information.

Acknowledgements

We are grateful to M. Wijnants, G. Van de Vijver and D. Van Dyck for excellent technical assistance. Financial support from FP7, H2020 and ERA-NET of the European Commission, IUAP of the Belgian Science Policy Office, and the University of Antwerp BOF is kindly acknowledged.

References

Hoshiba, Y., Wada, T., Hayashi-takagi, A. (2017) Synaptic ensemble underlying the selection and consolidation of neuronal circuits during learning. Front. Neural Circuits. 11:12
Klapoetke, N. C., Murata, Y., Kim, S. S., Pulver, S. R., Birdsey-Benson, A., Cho, Y. K., Morimoto, T. K., Chuong, A. S., Carpenter, E. J., Tian, Z., Wang, J., Xie, Y., Yan, Z., Zhang, Y., Chow, B. Y., Surek, B., Melkonian, M., Jayaraman, V., Constantine-Paton, M., Wong, G. K.-S., Boyden, E. S., Independent optical excitation of distinct neural populations. Nature Methods. 11(3): 338-46

Keywords: Memory, optogenetics, microelectrode array, rat model, in vitro, Cortex, Plasticity and Learning, Synapses

Conference: MEA Meeting 2018 | 11th International Meeting on Substrate Integrated Microelectrode Arrays, Reutlingen, Germany, 4 Jul - 6 Jul, 2018.

Presentation Type: Poster Presentation

Topic: Neural Networks

Citation: Giugliano M and Van De Vijver S (2019). Study of in vitro learning by neuronal ensembles through optogenetic stimulation. Conference Abstract: MEA Meeting 2018 | 11th International Meeting on Substrate Integrated Microelectrode Arrays. doi: 10.3389/conf.fncel.2018.38.00041

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Received: 13 Mar 2018; Published Online: 17 Jan 2019.

* Correspondence: Prof. Michele Giugliano, University of Antwerp, Biomedical Sciences, Antwerp, Belgium, michele.giugliano@uantwerpen.be