  The invariance of natural objects under perceptual changes is possibly
encoded in the brain by symmetries in the graph of synaptic connections. The
graph can be established via unsupervised learning in a biologically plausible
process across different perceptual modalities. This hypothetical encoding
scheme is supported by the correlation structure of naturalistic audio and
image data and it predicts a neural connectivity architecture which is
consistent with many empirical observations about primary sensory cortex.
