Monkey V1/V2 neuronal population response to drifting gratings with varying orientation and contrast

Correlated variability in the visual cortex is modulated by stimulus
properties. The stimulus dependence of correlated variability impacts
stimulus coding and is indicative of circuit structure. An affine model
combining a multiplicative factor and an additive offset has been proposed
to explain how correlated variability in primary visual cortex (V1)
depends on stimulus orientations. However, whether the affine model could
be extended to explain modulations by other stimulus variables or
variability shared between two brain areas is unknown. Motivated by a
simple neural circuit mechanism, we modified the affine model to better
explain the contrast-dependence of neural variability shared within either
primary or secondary visual cortex (V1 or V2) as well as the
orientation-dependence of neural variability shared between V1 and V2. Our
results bridge neural circuit mechanisms and statistical models, and
provide a parsimonious explanation for the stimulus-dependence of
correlated variability within and between visual areas.