Design and implementation of monolithic integrated electronic devices for the control and recordingof bidirectional multi-electrode arrays.

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The research project investigates the possibility of simultaneously stimulating and recording neural cells of the retina. This will be achieved by a multi-electrode array (MEA) that penetrates through all layers of the retina. The MEAs designed within this project will have more than one electrode per penetrating shank. Each electrode can be selected as either a stimulating or recording electrode, thereby allowing simultaneous stimulation and recording within a small area of tissue. From an engineering perspective it can present a breakthrough in the design of better implants due to the possibility of stimulation of different depths of tissue. An automatic stimulation parameter adaption based on the analyzed tissue will be possible. In the first phase of the project, the much reduced size of the electrodes in the MEA has proven that well-known stimulation techniques cannot be used without causing damage. A new stimulation technique has been invented to circumvent this problem and to permit safe stimulation of the retina using MEAs with small area electrodes. As required by the general project description, the new stimulation method is specifically designed to target retinal bipolar cells.The objectives of the proposed second phase of the project are firstly to complete the functional verification of the recording and stimulation chips, received at the end of the first funding phase, together with the current electrode array. Secondly, the generation of arbitrary stimulation signals will be included into the new stimulation technique and implemented in the new stimulator IC. The results of cell-biologic experiments on different cell layers, elaborated by our partners, will form the base for the specification of the new stimulator chip. Thirdly, together with the biomedical experimenters of subproject C and D the following questions will to be investigated:- Is it possible to stimulate different types of retinal nerve cells using the new stimulation technique and record their activity simultaneously? Is it also possible to limit the stimulation space parameters or to adapt the modulation concept during stimulation?- Are there any layer-specific stimulus waveforms and parameters which result in best behavior in relation to layer and place? What ist the best way of generating these waveforms?The results will guide the design of a CMOS-chip which performs the arbitrary stimulation as well as the recording functionality. During the project subgroup A will implemented this chip with a two dimensional basic structure for four penetrating shanks. It will be provided to subgroups C and D as a multi parameter configuration test board during the last third of the project.