Interpretation of correlated neural variability from models of feed-forward and recurrent circuits
Fig 1
Properties of response distributions and network scenarios.
A: Examples of distributions for which the variability is mostly along the diagonal direction (blue ellipse), resulting in a large value of σd, and for which the variability is mostly along the direction of the average response (red ellipse), resulting in a large value of σμ. B: Response distributions for two stimulus ensembles. Either σμ (red set) or σd (blue set) remains large across stimuli. A dependence as in the red set emerges in feed-forward models with common gain fluctuations, while a dependence as in the blue set may arise in densely connected recurrent networks or in feed-forward networks with shared inputs. C: Different network architectures which induce correlated activity. Connections (arrows) to and between neurons (dots) vary in strength. Dashed arrows indicate multiplicative modulations.