The recent paper “Decorrelated neuronal Firing in Cortical Microcircuits” published January 29, 2010 in Science takes a new look at correlated response fluctuations among simultaneously recorded neurons in the cerebral cortex.

This convincing study used very high quality simultaneous recordings from nearby neurons in the primary visual cortex to overcome technical challenges that may have contributed to a large body of literature that concludes that nearby neurons share significant common input based on correlated trial-to-trial variability in activity.

They saw correlations near zero using a number of different stimulus protocols and experimental conditions. They then went on to artificially introduce into their experiments some of the possible confounding factors and reproduced the significant correlations observed in earlier papers. The authors conclude that either 1) “adjacent neurons share only a few percent of their inputs” or 2) “their activity is actively decorrelated.”