Faculty Research and Publications

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Browsing Faculty Research and Publications by Subject "Adaptation"

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    Computational properties of the hippocampus increase the efficiency of goal-directed foraging through hierarchical reinforcement learning
    (Frontiers Media, 2016) Chalmers, Eric; Luczak, Artur; Gruber, Aaron J.
    The mammalian brain is thought to use a version of Model-based Reinforcement Learning (MBRL) to guide “goal-directed” behavior, wherein animals consider goals and make plans to acquire desired outcomes. However, conventional MBRL algorithms do not fully explain animals’ ability to rapidly adapt to environmental changes, or learn multiple complex tasks. They also require extensive computation, suggesting that goal-directed behavior is cognitively expensive. We propose here that key features of processing in the hippocampus support a flexible MBRL mechanism for spatial navigation that is computationally efficient and can adapt quickly to change. We investigate this idea by implementing a computational MBRL framework that incorporates features inspired by computational properties of the hippocampus: a hierarchical representation of space, “forward sweeps” through future spatial trajectories, and context-driven remapping of place cells. We find that a hierarchical abstraction of space greatly reduces the computational load (mental effort) required for adaptation to changing environmental conditions, and allows efficient scaling to large problems. It also allows abstract knowledge gained at high levels to guide adaptation to new obstacles. Moreover, a context-driven remapping mechanism allows learning and memory of multiple tasks. Simulating dorsal or ventral hippocampal lesions in our computational framework qualitatively reproduces behavioral deficits observed in rodents with analogous lesions. The framework may thus embody key features of how the brain organizes model-based RL to efficiently solve navigation and other difficult tasks.
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    Play fighting revisited: its design features and how they shape our understanding of its mechanism and functions
    (Frontiers Media, 2024) Pellis, Sergio M.; Pellis, Vivien C.; Ham, Jackson R.
    Play fighting has been one of the most intensely studied forms of play and so has provided some of our deepest insights into the understanding of play in general. As the label implies, this behavior resembles serious fighting, in that the animals compete for an advantage over one another, but unlike true aggression, for play fighting to remain playful, it also incorporates a degree of cooperation and reciprocity – restrained competition seems to be its hallmark. Despite these common features, it should be noted that both the advantage competed over and the mechanisms by which restraint is achieved varies across species. Such variation mitigates simple generalities. For example, how empirical support for a proposed adaptive function in one species not being replicated in another, is to be interpreted. What has emerged over the past few decades is that play fighting is diverse, varying across several dimensions, some superficial, some fundamental, making choosing species to compare a challenge. In this paper,we explore various design features that constitute play fighting and the ways these can be modified across different species and lineages of species. Given that a major pillar of ethology is that description precedes explanation, having a good grasp of the behavioral diversity of play fighting is an essential starting point for detailed analyses of the mechanisms and functions of play. We show that commonalities across species likely involve different mechanisms than do species idiosyncrasies, and that different styles of play fighting likely afford different adaptive opportunities