Interdisciplinary studies of decision-making and motor planning

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Most theories of decision-making suggest that the brain first builds abstract representations of choices in terms of subjective values, costs, risks, etc., then uses these to select a goal, and finally transforms that goal into a movement command. However, a growing body of neural data increasingly casts such classical serial frameworks into doubt. Part of the reason, I believe, is that the brain is the product of a long history of evolution, during most of which animals were faced with challenges very different from those of abstract cognition. For example, most decisions in animal life are made in a real-time, dynamically changing environment, which does not allow time for careful deliberation followed by action planning. For effective behavior in such dynamic situations, the brain requires a parallel architecture in which multiple potential actions can be specified simultaneously, one selected on the basis of continuously changing sensory information, and all the while other options continue to remain under consideration in case circumstances suddenly change. To deal with such situations, I've proposed the "affordance competition hypothesis", which suggests that the functional organization of behavior is a parallel architecture whereby sensory information is processed to specify several potential actions that compete against each other in sensorimotor circuits while other systems collect information for biasing that competition to select a winning action. My research program focuses on testing and further developing this broad theoretical framework. I address these goals through an interdisciplinary approach that integrates computational modeling with a range of experimental techniques, including multi-electrode recording in awake, behaving monkeys, as well as human behavioral, imaging, and transcranial magnetic stimulation studies. My NSERC Discovery Grant supports the computational projects as well as experimental studies with human subjects. Current projects fall into three general themes. Theme #1 addresses how the brain makes decisions in a dynamically changing environment, and will involve developing a computational model on the basis of existing data from CIHR-funded neural recording experiments in monkeys as well as NSERC-funded magnetoencephalography (MEG) in humans. Theme #2 generalizes these ideas toward higher-level decisions, but still framed within a natural context. In particular, we will launch a new series of MEG studies in humans to investigate "foraging" choices between engaging currently available opportunities versus searching for new opportunities elsewhere. Theme #3 addresses a very novel line of research: how decisions are made while we are already acting. This builds on behavioral paradigms we pioneered in the previous funding cycle of my Discovery Grant, which we will extend toward investigating neural mechanisms through the use of transcranial magnetic stimulation in humans during a variety of manual tracking tasks.