Neural coding and functional organization of the octopus visual system

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ABSTRACT Cephalopods have large and complex brains, and in particular a highly capable visual system. However, their brains evolved independently from vertebrates, and very little is known about how neural circuits in the cephalopod brain process visual information. In fact, there has never been a direct recording of receptive fields in the central visual system of cephalopods. This study will measure neural activity and visual coding in the optic lobe of Octopus bimaculoides, an emerging model organism for cephalopod research. The first aim will employ two-photon calcium imaging in the optic lobe of juvenile octopuses, combined with controlled visual stimuli, to measure receptive field properties in large ensembles of individual neurons. The second aim will combine this functional imaging with anatomical connectivity, identified via retrograde tracing, to determine how visual information is routed through the visual system and into higher brain regions associated with specific behaviors. The third aim will incorporate these experimental results into computational analysis of the visual features being encoded, and into network models of visual processing. Together, these aims will provide direct insight into the neural coding and functional organization of this unique visual system. This work will be the first to describe neural computations in the central visual system of cephalopods. Examination of a system that is evolutionarily distinct, yet functionally parallel to the vertebrate system, has the potential to illuminate novel ways by which visual processing can be carried out. Likewise, observation of convergence of functional organization in cephalopods, relative to vertebrates and other invertebrates, such as Drosophila, would help identify key features necessary for the function of complex visual systems.