Arrays of 60 Ti/Au/TiN extracellular electrodes with electrode spacing/diameter 500/30 μm, were used [Multi Channel Systems (MCS), Reutlingen, Germany]. A commercial amplifier (MEA-1060-inv-BC, MCS) with frequency limits of 150–3000 Hz and a gain of ×1024 was used to reduce noise. Data was digitized with an acquisition board (PD2-MF-64-3M/12H, UEI, Walpole, MA, USA) and sampled at a frequency of 16 Ksample/s per channel. Monophasic, 200 μs square pulse 100–1000mV voltage stimulation through extracellular electrodes was performed (Wagenaar et al., 2004 (link)), using a dedicated stimulus generator (STG 1004, MCS). Data pre-processing and online event detection were performed using a Simulink-based (The Mathworks, Natick, MA, USA) xPC target application (see Zrenner et al., 2010 (link) for details). Extracellular spikes were detected online by threshold crossing (8 × STD) of the raw voltages. Spike times and shapes, as well as −10 to +50 ms voltage traces triggered by each stimulus, were recorded from all electrodes. When we state the number of used networks, this is congruent with the number of experiments. The data were analyzed by custom MATLAB scripts (The Mathworks, Natick, MA, USA).
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