add info for intracellular data

single_cell_intracellular_spikes/readme.md

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+# Content
+The NIX file contains intracellular and spike time data recorded in a midbrain neuron of the weakly electric fish *Apteronotu leptorhynchus*
+
+Data was recorded in the [Neuroethology](https://neuroetho.uni-tuebingen.de) group at the University of Tübingen