Mullers Law of specific nerve energies introduced the idea that nerves transmit information about specific sensory features. This concept has been refined by the notion of 'labeled lines,' specific cells that capture sub-features of a sensory or motor stimulus, such as Hubel and Weisel's opponent color cells. Such features can be visualized as coding a signed quantity that has positive and negative components that are encoded with separate nerve cells. We show that there are two important consequences when learning receptive field using signed codings in circuits. The first is that in feedback circuits even simple operations need to be distributed across multiple distinct pathways. The second consequence is that such pathways are necessarily dynamic. Synaptic weights change during learning and must break and grow new circuit connections because the weights need to change sign during receptive field formation
