Increased neuron density in the midbrain of a foveate bird, pigeon, results from profound change in tissue morphogenesis.

The increase of brain neuron number in relation with brain size is currently considered to be the major evolutionary path to high cognitive power in amniotes. However, how changes in neuron density did contribute to the evolution of the information-processing capacity of the brain remains unanswered. High neuron densities are seen as the main reason why the fovea located at the visual center of the retina is responsible for sharp vision in birds and primates. The emergence of foveal vision is considered as a breakthrough innovation in visual system evolution. We found that neuron densities in the largest visual center of the midbrain - i.e., the optic tectum - are two to four times higher in modern birds with one or two foveae compared to birds deprived of this specialty. Interspecies comparisons enabled us to identify elements of a hitherto unknown developmental process set up by foveate birds for increasing neuron density in the upper layers of their optic tectum. The late progenitor cells that generate these neurons proliferate in a ventricular zone that can expand only radially. In this particular context, the number of cells in ontogenetic columns increases, thereby setting the conditions for higher cell densities in the upper layers once neurons did migrate.

[The management of diabetic retinopathy and diabetic macular edema; joint forces fight for sight]. / Prise en charge de la rétinopathie diabétique: un combat pour la vue.

Despite the considerable progress in prevention and treatement options since the first big epidemiologic studies in the 80's, diabetic retinopathy still represents the primary cause of blindness in the working age population. The intensified prevention efforts that took place recentyears did show hopeful results as the incidence of diabetic retinopathy seems to decline. However a still considerable number of patients does not meet metabolic or treatment recommandations. In the aftermath of an ongoing globalisation and growing urbanisation of the society, there is an even bigger need of understanding the disease as well as improving prevention and treatment guidelines.