We show that under suitable assumptions (primarily linearization) a simple and perspicuous online learning rule for Information Bottleneck optimization with spiking neurons can be derived. This rule performs on common benchmark tasks as well as a rather complex rule that has previously been proposed. Furthermore, the transparency of this new learning rule makes a theoretical analysis of
its convergence properties feasible. A variation of this learning rule (with sign changes) provides a theoretically founded method for performing Principal Component Analysis (PCA) with spiking neurons. By applying this rule to an ensemble of neurons, different principal components of the input can be extracted. In addition, it is possible to preferentially extract those principal components from incoming signals X that are related or are not related to some additional target signal YT. In a biological interpretation, this target signal YT (also called relevance variable) could represent proprioceptive feedback, input from other sensory modalities, or top-down signals.