Review articleTowards building a more complex view of the lateral geniculate nucleus: Recent advances in understanding its role

- Recent advances in understanding the role of LGN emphasize that it can no longer be considered a simple linear spatiotemporal filter.
- The LGN has a variety of complex nonlinear behaviors. Perhaps the most interesting nonlinearity involves feedback from cortex.
- Many current models of high-level vision have ignored the role of LGN.
- We suggest further development of feedback models of high-level vision considering LGN function.
- Predictive coding and expectation coding models are in this direction.

The lateral geniculate nucleus (LGN) has often been treated in the past as a linear filter that adds little to retinal processing of visual inputs. Here we review anatomical, neurophysiological, brain imaging, and modeling studies that have in recent years built up a much more complex view of LGN. These include effects related to nonlinear dendritic processing, cortical feedback, synchrony and oscillations across LGN populations, as well as involvement of LGN in higher level cognitive processing. Although recent studies have provided valuable insights into early visual processing including the role of LGN, a unified model of LGN responses to real-world objects has not yet been developed. In the light of recent data, we suggest that the role of LGN deserves more careful consideration in developing models of high-level visual processing.