How a frog's neuronal wetware learns what is where in the dark

The clawed frog \emph{Xenopus}, an inhabitant of South-African ponds, locates prey by detecting water waves generated by insects floundering on the water surface. It does so during night by means of 180 lateral-line organs located on its skin, which allow the frog not only to localize prey but also to determine its character. We have shown [1] how it performs both through waveform reconstruction. A key question is now how it gets the appropriate neuronal wetware. In so doing, catching time differences arising from the input on its skin is important. Spike-timing-dependent synaptic plasticity (STDP) [2], which has been experimentally demonstrated, seems to be the natural tool. The development of the frog's synaptic software appears to be ``supervised'' by the visual system during daytime. Here we show how supervised STDP allows a frog to learn what is where in the dark. In addition, the learning procedure is derived from a minimization principle and can be generalized to perform similar tasks elsewhere. Refs: [1] J.-M.P. Franosch, M.C. Sobotka, A. Elepfandt, and J.L. van Hemmen, Phys. Rev. Lett. 91 (2003) 158101; [2] W. Gerstner, R. Kempter, J.L. van Hemmen, and H. Wagner, Nature 383 (1996) 76.