MURRAY, JA; U Central Arkansas: Advances in the neural bases of orientation & navigation

The ability to locomote in one direction, and the ability to navigate toward a distant goal are related behaviors that are phylogenetically widespread. Orientation includes finding the source of a signal, or movement relative to directional cues. Such abilities may require little more than directionally-selective sensors coupled to turning mechanims, so this behavior can be implemented by relatively-simple circuits. Navigation involves both the ability to detect direction, as well as a map-sense that provides position. Navigation is less-common and arguably requires greater brain computation than simple orientation, but may be present in arthropods as well as in vertebrates. Great progress has been made in exploring the biophysical and sensory bases for these behaviors, and in recent years the locations and the identity of the cellular transducers of the sensory stimuli (e.g. geomagnetic fields) have been narrowed in some taxa. The sea slug Tritonia orients its crawling to chemical, hydrodynamic, and geomagnetic cues. Its brain has ~7,000 relatively-large neurons that facilitate circuit analysis. Recent work has characterized both peripheral and central neural correlates of orientation signals, as well as the control of thrust and turning, and studies of their field behavior have suggested how these disparate orientation systems may be integrated. Direction-selective and position-responsive brain cells have been located in the brains of mammals and birds, and these cells may contribute to a cognitive map that can enable navigation. Navigation strategies inspired from organisms have been implemented in autonomous robots, and programming a strategy into a computer may be analogous to the evolutionary trade-offs between robustly simple neural circuits and more complex neural systems that are more physiologically expensive. The synergy between robotic models and physiology has advanced both fields.