An interesting article in PLOS Biology about how the brain adapts to sensory deprivation. Cells in layer 2/3 became less active after deprivation. Cells in layer 5 compensated by being less inhibitory over L2/3 cells, but cells in layer 1 became (slightly) more inhibitory. The theory is that the L5 activity is an auto-regulation process, whereas the L1 activity is a top-down inhibition (i.e. from elsewhere in the brain) as the L2/3 cells were now essentially amplifying noise. The paper is available and has a lot more information (e.g. there seems to be a reciprocal relationship between inhibition in L1 and L5).