How the cat\'s thalamus changes what the cat\'s retina tells the cat\'s brain

All visual information gathered by the photorreceptors in the retina has to necessarily pass through the lateral geniculate nucleus (LGN) of the thalamus to reach the visual areas of the cerebral cortex where our subjective experience (our vision) of the world emerges. What exactly the LGN contributes to visual processing is still a matter of intense debate. Mostly, because the antagonistic center-surround structure of the LGN receptive fields can hardly be distinguished from that of their retinal inputs. However, since retinal ganglion cells are all excitatory, the precise spatio-temporal structure of the LGN receptive fields cannot be directly inherited from the retina. Instead, it must be recreated through the synaptic interaction of retinal afferents, local inhibitory neurons and thalamocortical cells. In cat, these three elements appear in uneven numbers, which could be consistent with a wide range of potential retino-thalamic circuits, each with a unique capacity to transform the retinal output before it reaches the primary visual cortex. Using a combination of whole-cell recordings in vivo and computational techniques we have explored this retinogeniculate rewiring and found experimental evidence for a circuit design that optimizes resolution and reduces redundancy in the retinal message on its way to the cortex.