Carl van Vreeswijk
It has been shown that the receptive fields of simple cells in VI can be ex(cid:173) plained by assuming optimal encoding, provided that an extra constraint of sparseness is added. This finding suggests that there is a reason, in(cid:173) dependent of optimal representation, for sparseness. However this work used an ad hoc model for the noise. Here I show that, if a biologically more plausible noise model, describing neurons as Poisson processes, is used sparseness does not have to be added as a constraint. Thus I con(cid:173) clude that sparseness is not a feature that evolution has striven for, but is simply the result of the evolutionary pressure towards an optimal repre(cid:173) sentation.