Theory of orientation tuning in visual cortex.

TLDR

Intrinsic cortical connections and their role in sensory processing and behavior remain poorly understood. The authors analyze a simple network model that combines orientation‑selective input from the lateral geniculate nucleus with orientation‑specific cortical interactions. The model predicts that cortical interactions can generate sharp orientation tuning independent of LGN anisotropy, with tuning width largely unaffected by contrast or stimulus anisotropy, a slow virtual rotation in transient responses, and orientation‑dependent long‑tailed cross‑correlations.

Abstract

The role of intrinsic cortical connections in processing sensory input and in generating behavioral output is poorly understood. We have examined this issue in the context of the tuning of neuronal responses in cortex to the orientation of a visual stimulus. We analytically study a simple network model that incorporates both orientation-selective input from the lateral geniculate nucleus and orientation-specific cortical interactions. Depending on the model parameters, the network exhibits orientation selectivity that originates from within the cortex, by a symmetry-breaking mechanism. In this case, the width of the orientation tuning can be sharp even if the lateral geniculate nucleus inputs are only weakly anisotropic. By using our model, several experimental consequences of this cortical mechanism of orientation tuning are derived. The tuning width is relatively independent of the contrast and angular anisotropy of the visual stimulus. The transient population response to changing of the stimulus orientation exhibits a slow "virtual rotation." Neuronal cross-correlations exhibit long time tails, the sign of which depends on the preferred orientations of the cells and the stimulus orientation.