An uncorrelated state for the cortex?

The spike trains of nearby neurons in the sensory cortex are typically thought to be correlated due to mutual connections and common input. Multiple studies have measured these correlations and found them to be substantial (in the range of 10-40%). Two recent papers, however, reported that average correlations can be an order of magnitude smaller. Such low correlations could indicate an ‘uncorrelated state’ for the cortex, where cortical neurons act independently even in the face of strong common input.