Dartmouth Events

Please join us in Kellogg 200 to hear the latest research from Dr. Erik Duboué,

 “Evolution of neural circuitry in the blind cavefish"

Evolution of the brain is a fundamental principle to adaptation in novel environments. Comparative studies have increased our knowledge of the impact of evolution on the vertebrate brain, yet large divergence times and lack of molecular and genetic tools impede our understanding of how changes in the anatomy and function of precise neuronal circuits cause adaptive behaviors to emerge. We have identified a neuroanatomical area underlying light sensitivity in the blind Mexican cavefish, Astyanax mexicanus, and are using it to study how evolution alters behavior. Astyanax is unique among model systems in that there are two divergent forms, an ancestral surface form and at least 30 populations of cave-dwelling conspecifics. We find that both surface and cave fish have retained the ability to detect changes in photo-illumination, yet whereas surface fish become hyperactive when lights are removed, cavefish become hyperactive when lights turn on, presumably an adaptation to the perpetual darkness of a cave. Using a novel whole brain neuroanatomical atlas and newly developed genetic tools for monitoring neuronal activity, we have identified a neural circuit modulating light responsiveness. We assessed the volumes of every known neuroanatomical locus of the brain and correlated their size to light sensitivity. Further, using functional mapping of neuronal activity, we found a region of the brain whose neuronal activity may explain differences in light preference. To determine the spatiotemporal dynamics of neuronal activity in this region we are performing functional imaging using pan-neuronal GCaMP in transgenic Astyanax. Our findings reveal how changes to a defined neuronal circuit modulate light sensitivity and establish a model in which genetic changes in natural populations can be associated with changes in anatomy and function of the vertebrate brain, leading to an evolutionary adaptation of behavior.