Imagine yourself hiking in the trailless wilderness of northern Scandinavia. You leave your tent for an excursion to admire the beautiful scenery. After passing the first moss-covered hill you already lose sight of the tent. Most humans would be utterly lost within an hour of undirected travel, unable to find the way back. Yet, many tiny invertebrate animals, such as bees and ants, with even smaller brains are able to return back to their nests with ease, even after navigating unknown, featureless terrain. They use a navigational neural computation called path integration to do so, which other animals, including mammals, rely on as well. Path integration is an efficient strategy to find a previously visited location: An animal monitors the turns it makes and distances it travels along its trip to continuously update an estimate of its location relative to the start of its journey. This estimate can be used to return to home along a straight line, termed the home vector. Besides returning home, path integration can be used to locate any previously visited location when defined as the origin, a strategy generally called vector navigation. In addition to following a home vector, some arthropods are able to construct novel shortcuts to previously known locations and use landmarks as navigational aids. Observing these impressive behaviors raises the question of how they are neurally manifested in the relatively simple brains of arthropods, some smaller than a pinhead. Much progress has been gained in unravelling the behavioral strategies of vector navigation in animals, the neural circuits responsible for compass and speed encoding required for insect navigation, and in the development of models for how neural circuits might manifest into navigation behaviors; however, the neural basis of vector memories underlying path integration remains unknown in any animal. My project aimed to fill this gap in knowledge, with the ultimate goal of elucidating the neural basis of path integration memory, a question that has been asked for decades. Combining behavioral, electrophysiological and neuroanatomical methods, I aimed at uncovering the core circuits underlying vector navigation in arthropods as an overarching goal. Over the course of the proposed project, I pursued two specific goals, first to develop a behavioral assay to define the fundamental characteristics of path integration in bumblebees and second, to develop methods to determine the neural correlate of vector memories in bumblebees.
