Blind cavefish retain functional connectivity in the tectum despite loss of retinal input

Sensory systems display remarkable plasticity and are under strong evolutionary selection. The Mexican cavefish, Astyanax mexicanus, consists of eyed river-dwelling surface populations and multiple independent cave populations that have converged on eye loss, providing the opportunity to examine the evolution of sensory circuits in response to environmental perturbation. Functional analysis across multiple transgenic populations expressing GCaMP6s showed that functional connectivity of the optic tectum largely did not differ between populations, except for the selective loss of negatively correlated activity within the cavefish tectum, suggesting positively correlated neural activity is resistant to an evolved loss of input from the retina. Furthermore, analysis of surface-cave hybrid fish reveals that changes in the tectum are genetically distinct from those encoding eye loss. Together, these findings uncover the independent evolution of multiple components of the visual system and establish the use of functional imaging in A. mexicanus to study neural circuit evolution.

Automated summary

The Mexican cavefish Astyanax mexicanus provides an opportunity to study the evolutionary changes in sensory circuits in response to environmental perturbation. The study shows that the functional connectivity of the optic tectum in cavefish remains largely unchanged except for the loss of negatively correlated activity, indicating the resistance of positively correlated neural activity to the loss of input from the retina. Additionally, the changes in the tectum are found to be genetically distinct from the encoding of eye loss.