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A5: Defined stimulus-response functions in active networks

Ulrich EgertR, Alfred StettW


R
= Biomicrotechnology
W = NMI Natural and Medical Sciences Institute, Tübingen


Scientific background

With the intense research towards implanted neurotechnical devices for sensory prostheses or for therapeutic stimulation, the mechanisms underlying electrical stimulation have gained renewed attention. Though the basic biophysical aspects have been described to some detail, it is not clear how a desired neuronal response can be defined and translated into the stimulation paradigm necessary to evoke it. While suitable locations for effective stimulation are known in some cases, the network mechanisms underlying successful result remain mostly hypothetical. Adjusting brain pacemakers or similar devices therefore largely relies on therapeutic efficacy determined by trial and error. In particular with low-power stimuli with good long-term biocompatibility, the interaction between stimulus effect and intrinsic activity of the local network limits reproducibility of the results. Understanding what limits stable stimulus-response relations and how network dynamics govern stimulus-response transfer functions will help to optimize the interaction with these networks. In prior work, we developed microelectrode arrays for stimulation and recording from cultured networks and acute brain slices. These were used to optimize electrodes, and to define stimulation paradigms for retinal implants and feedback-driven hybrid circuits. The influence of long-term patterns of spontaneous activity in cultured networks on stimulation outcome in feedback configurations is currently tested at the BCCN Freiburg.


Objectives

We aim to identify the transfer properties of electrical stimulation into network responses at different temporal and spatial scales, to characterize the interaction of ongoing activity with the stimuli, and to optimize the induction to obtain defined network responses.

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