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Action Selection under Contextual Uncertainty: the Role of Learning and Effective Connectivity in the Human Brain

Final Report Summary - ACTSELECTCONTEXT (Action Selection under Contextual Uncertainty: the Role of Learning and Effective Connectivity in the Human Brain)

In a changing world, our brains have to deal with several sources of information to form estimates about what is likely to happen, and when it might happen. If successful, this allows for preparation and selection of appropriate action in response to, or anticipation of events in the world. However, the mechanistic underpinnings through which our brain forms beliefs about the rules governing the world, and then uses these beliefs to select the best actions, among many alternatives, had remained largely unknown. ActSelectContext was designed to address this shortcoming in our knowledge. Specifically, the project focused on two types of uncertainty we are often faced with: uncertainty about what might happen, and uncertainty about when things happen. Specifically, it asked whether the beliefs about uncertainty influence the human action system, and the specific conditions under which this influence occurs. Moreover, the project sought to establish not only the processes that might govern uncertainty computations and action selection, but also whether these processes (and the brain regions associated with these) are indeed necessary. To address this question, ActSelectContext employed a series of interventional approaches, including non-invasive brain stimulation, human pharmacology, and computational modelling.
The research in this project was carried out with complementary and mutually reinforcing methodologies, including novel developments made throughout the project: computational modelling, brain imaging, neurostimulation, and pharmacological interventions. This demonstrated that our motor system is indeed continuously influenced by beliefs about what might happen in the world. These beliefs inform, at a neurophysiological level, action representations in premotor and motor cortex. Moreover, decision processes themselves depend on whether they occur in the context of a required action, or are liberated from such requirements. Several neurotransmitters, including Dopamine, Noradrenaline, and Acetylcholine, play important roles in computing uncertainty estimates, and how these inform the selection of our actions, thus providing important insight into the possible mechanism through which out brain controls such behaviours. These results were broadly confirmed both for uncertainty computations about what will happen (eg reward information) and when it will occur (ie temporal processing), suggesting that some fundamental principles exist in how our brain forms estimates about uncertainty, and then communicates these to the motor system so that appropriate actions can be selected. ActSelectContext also provided evidence that this communication occurs through multiple anatomical routes, which depend on the specific requirements in which uncertainty estimates have to be formed (eg uncertainty about reward or time). Perturbation of these systems through brain stimulation or pharmacological interventions provided some interventional evidence that without the ability to form uncertainty estimates, specific aspects of action selection and preparation are not possible. Finally, in order to push the boundaries of how we can assess and measure brain activity and thus the mechanisms through which our brain transforms beliefs into actions, we have worked on novel so-called high precision MEG approaches that now allow for recordings of brain activity in humans with much improved precision.
In summary, by using complementary approaches and novel methodologies, the project contributed to our understand about how our brain deals with uncertain information, forms decisions based on estimates of uncertainty, and how this information is used to inform movement related brain regions about the best movement to select.