Chronic recording of brain activity in awake toads.

Abstract

<h4>Background</h4>Amphibians represent an important evolutionary transition from aquatic to terrestrial environments and they display a large variety of complex behaviors despite a relatively simple brain. However, their brain activity is not as well characterized as that of many other vertebrates, partially due to physiological traits that have made electrophysiology recordings difficult to perform in awake and moving animals.<h4>New method</h4>We implanted flexible mesh electronics in the cane toad (Rhinella marina) and performed extracellular recordings in the telencephalon of anesthetized toads and awake toads over multiple days.<h4>Results</h4>Though we struggled with maintaining implants in all operated animals, we recorded brain activity over five consecutive days in 5 awake toads and over a 15 week period in a toad that was anesthetized during recordings. We were able to perform spike sorting and identified single- and multi-unit activity in all toads.<h4>Comparison with existing methods</h4>To our knowledge, this is the first report of a modern method to perform electrophysiology in non-paralyzed toads over multiple days, though there are historical references to short term recordings in the past.<h4>Conclusions</h4>Optimizing flexible mesh electronics in amphibian species will allow for advanced studies of the neural basis of amphibian behaviors.