Role of correlations in population coding
  Correlations among spikes, both on the same neuron and across neurons, are ubiquitous in the brain. For example cross-correlograms can have large peaks, at least in the periphery, and smaller -- but still non-negligible -- ones in cortex, and auto-correlograms almost always exhibit non-trivial temporal structure at a range of timescales. Although this has been known for over forty years, it's still not clear what role these correlations play in the brain -- and, indeed, whether they play any role at all. The goal of this chapter is to shed light on this issue by reviewing some of the work on this subject. 
Peter E. Latham and Yasser Roudi
q-bio.NC q-bio.QM