The origin and evolution of bilaterian brains

Den fremre delen av det sentrale nervesystemet hos dyr, hjernen, koordinerer essensielle funksjoner slik som å oppfatte miljøet rundt seg, ta avgjørelser, samt koordinering av bevegelser og læring. Menneskehjernen består av forskjellige deler som har oppstått på ulike tidspunkt i løpet av dyrerikets evolusjon. Til tross for at hjernen er en essensiell komponent i evolusjonshistorien, er ikke opprinnelsen og evolusjonen av de ulike delene i hjernen godt beskrevet. Det er for eksempel fremdeles et åpent spørsmål hvordan ulike deler av hjernen hos fluer kan være beslektet med deler av menneskehjernen.

The brain, the anterior part of the central nervous system of animals, coordinates essential functions of an animal including the reception of the environment, the coordination of movements and learning and decision making. Although the brain is a key-innovation in evolutionary history, its origin and further diversification into the complex, multiple-lobed anterior nerve centralizations with millions of neurons of a broad range of animals has not been elucidated. Our knowledge of brain development and evolution is mainly based on work performed in prominent model systems including vertebrates (fish, frog and mouse) and invertebrates that are distantly-related and considered to be highly derived (Drosophila and C. elegans). The project proposed herein aims to study brain development in a variety of highly informative animal taxa, with the ultimate aim of reconstructing the history of brain diversity during animal evolution. We aim to test current hypotheses of brain evolution (‘tripartite-brain’, ‘chimeric brain’) using the comparative approach using the current phylogenetic framework. Our approach combines advanced bioinformatics, molecular methods and behavioral experiments, and will be carried out in eight representative species belonging to under-investigated animal phyla. We will describe the morphological and molecular composition of brains in these species and integrate it with novel fossil data from Chengjiang provided by our collaborator. Using this information we will be able to infer the morphology, molecular patterning and possibly the cell type composition of ancestors at six important nodes in the animal tree of life. We will also be able to comprehend when shifts in brain evolution have occurred and how these shifts have remodeled the animal body plans and ultimately their behavioral complement.