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Sunday, July 19 • 8:00pm - 9:00pm
P195: Associative memory performance in peripherally-lesioned networks repaired by homeostatic structural plasticity

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Ankur Sinha, Christoph Metzner, Rod Adams, Neil Davey, Michael Schmuker, Volker Steuber

Google Meet link: https://meet.google.com/zek-rkja-voy

In spite of a plethora of peripheral lesion experiments documenting that structural plasticity causes large scale changes in brain networks [1, 3, 4], our understanding of the mechanisms of structural plasticity remains limited. Structural plasticity acts over extended periods of time, albeit at a slow rate, to modify network connectivity by the formation and removal of synapses. Alterations in network connectivity are expected to affect network function, but the resulting functional consequences of structural plasticity have not been studied in detail.

To study the activity dependent growth characteristics of neurites, which underlie network reconfiguration, we previously developed a novel model of peripheral lesioning and subsequent repair in a balanced cortical Asynchronous Irregular (AI) spiking network [6]. The network used in our model, which represents a physiological brain network, was selected since it has been demonstrated to function as an attractor-less associative memory store [5]. Using this new model, we investigated the functional effects of repair mediated by homeostatic structural plasticity on the network. We stored associative memories in the network and recalled them at different stages of the simulation by stimulating a random subset of their neurons: before deafferentation, after deafferentation but before repair, and after deafferentation during repair. At each recall, recall performance was quantified using a Signal to Noise ratio (SNR) metric [2].

Associative memories that include neurons deafferented by the peripheral lesion experience a reduction in their recall performance proportionate to the number of deprived neurons. Our results indicate that while structural plasticity restores activity of deafferented neurons to pre-injury levels, it does not restore the performance of the stored associative memories. This suggests that associative memories stored before a peripheral lesion are not necessarily protected in the repair process. Further research is needed to explore whether the repair process can be modulated to retain the performance of the stored associative memories.

References
1. Rasmusson, D. D. Reorganization of raccoon somatosensory cortex following removal of the fifth digit. Journal of Comparative Neurology 205, 313–326 (1982).
2. Dayan, P. & Willshaw, D. J. Optimising synaptic learning rules in linear associative memories. Biological Cybernetics 65, 253–265 (1991).
3. Keck, T., Mrsic-Flogel, T. D., Afonso, M. V., Eysel, U. T., Bonhoeffer, T. & Hübener, M. Massive restructuring of neuronal circuits during functional reorganization of adult visual cortex. Nature neuroscience 11, 1162–1167 (2008).
4. Keck, T., Scheuss, V., Jacobsen, R. I., Wierenga, C. J., Eysel, U. T., Bonhoeffer, T., et al. Loss of sensory input causes rapid structural changes of inhibitory neurons in adult mouse visual cortex. Neuron 71, 869–882. ISSN : 0896-6273. (2011).
5. Vogels, T. P., Sprekeler, H., Zenke, F., Clopath, C. & Gerstner, W. Inhibitory plasticity balances excitation and inhibition in sensory pathways and memory networks. Science 334, 1569–1573. (2011).
6. Sinha, A., Metzner, C., Davey, N., Adams, R., Schmuker, M. & Steuber, V. Growth Rules for the Repair of Asynchronous Irregular Neuronal Networks after Peripheral Lesions. bioRxiv. eprint: nttps://www.biorxiv.org/content/early/2019/10/21/810846.full.pdf. (2019).

Speakers
avatar for Ankur Sinha

Ankur Sinha

Research Fellow, University College London, UK



Sunday July 19, 2020 8:00pm - 9:00pm CEST
Slot 12