The research outlines a behavioral, neurophysiological and anatomical study of the optic tectum of the teleost Astyanax mexicanus as a model for the study of the evolution of coding. Astaynax is exceptionally good animal model because this species has two distinct phenotypes, an ancestral river dwelling form and a derived cave dwelling form. The polarity of evolutionary changes and the environmental conditions leading to the cavefish phenotype are known with certainty, and several different cavefish populations have evolved independently. Theregressive change for this study is eye degeneration. Although adult cavefish lack functional eyes, small eye primordia form during embryogenesis, which later arrest in development, degenerate, and sink into the orbit. Remarkably, cave Astyanax lens transplantation from embryonic river fish donors, allowing for the emergence of a restored cornea, iris, and retinal photoreceptor cells). Furthermore, preliminary data suggest that retinal projections are expanded and the corresponding optic tectum is enlarged.
In this program of study all experiments will be performed in adult river, cave, and transplanted fish. Goal 1) To determine visual acuity using behavioral tests. Optomotor responses are idea for this end because they can be used to measure different aspect of visual acuity such as spatial, temporal resolution and luminescence. Goal 2) To describe anatomical circuitry of the tectum of  using  tract tracing, biolostics and immunohistochemistry techniques.  will provide connectivity, cell morphology and protein expression characteristics of the tectal circuitry. Goal 3) To characterize physiological responses in the retina and optic tectum. Electroretinogram and in vivo recordings from the 3 different groups of fish will determine the extent in which coding in the retina gets transformed into to coding in the optic tectum.
The modifications introduced via adaptation to specific ecological niches can sometimes point to which structures and functions are responsible for the novel behavior or specialization. Therefore, the study of Astyanax allows for the understanding of relationships between structure and function, and provides hints about neural coding strategies.