Basic anthropometry and health status of elderly: findings of the Maracaibo Aging Study.

Vertebrate central nervous systems share common structural, developmental, and genetic blueprints. This standard architecture must accommodate species-specific differences in dominant sense(s), modes of locomotion, and strategies for food seeking, predator avoidance, and reproduction. Such profound differences in functional requirements can exist for species that are closely related by phylogeny, highlighting the need for plasticity in the common blueprint of the brain. Recent technological developments allow exploration of how such adaptations arise with unprecedented resolution. On the one hand, large-scale recordings of neuronal populations facilitate an unbiased comparison of information channels across species, linking coding strategies to ecological niches. On the other, high-throughput single-cell transcriptomics allows comprehensive identification of cell types and cross-species comparisons. With these techniques in hand, it becomes possible to describe the process of central nervous system evolution by tracing changes in cell-type complement and adaptations in computational characteristics. Here, we apply this approach to a comparison of the early visual system in two closely related murid rodents. The laboratory mouse () is a popular model for understanding mammalian vision in health and disease and for establishing general principles of neural function. Like most murid species, are predominantly nocturnal, and this is reflected in key features of the visual system, including a rod dominant retina and a UV-transmitting lens. However, some Muridae are day-active, including the four-striped mouse, , of sub-Saharan Africa. The switch to daytime activity in has been associated with substantial changes in visual system anatomy. The retina is cone dominated, its lens absorbs UV light, and both its retina and visual centers in the brain are expanded in volume compared with . Moreover, an unbiased analysis of the genome reveals that genes involved in vision exhibit accelerated evolution compared with related murids. and represent a case study in how differences in temporal niche are reflected in visual system anatomy. However, an important unanswered question is how such anatomical expansion impacts the visual code. In principle, the enhanced capacity to process visual information in could allow the same computations to be performed with higher precision; a wider array of visual features to be extracted, describing the scene with greater granularity; or reconfigurations of the visual code toward features of particular ecological importance. Similarly, contributors to the anatomical expansion remain unclear. For example, both inner nuclear and ganglion cell layers are thicker in the retina, but the increased cell number might be accompanied by altered frequencies of cell types shared with , emergence of new types, or both. Addressing these questions will help reveal how the blueprint of neural circuits can be adjusted to align computation to changing ecology.