Klein-Fluegge, M; (2014) Interaction of Decision Making and Action Planning in the Human Brain. Doctoral thesis , UCL (University College London).

Abstract

This thesis examines how the human brain translates decisions between differently valued outcomes into the ensuing motor responses. Our work resides at the interface between two fields of study, value-based decision making and action selection, which have been regarded as one process by some and considered entirely separate by others. But the underlying neuro-anatomical substrates likely depend on the exact type of choice we face. We conduct a series of studies to specifically explore the temporal relationship of value-comparison and motor preparation, the regions at the interface between abstract choice and action, and the integration of both action-related and abstract reward information for computing a choice. In the first study, we exploit the high temporal resolution of transcranial magnetic stimulation (TMS) to show that primary motor cortex (M1) receives continuous updates about a decision process. Critically, this argues against a serial processing of decision and action. The second study uses TMS to probe trial-by-trial variability as a marker of motor preparation in M1. We demonstrate that during choice processing, a decrease in variability prepares M1 to issue a motor response. The third experiment uses functional magnetic resonance imaging (fMRI) to investigate brain regions and functional interactions that mediate the transformation of abstract choice signals into action commands. We propose a role for intraparietal cortex as one of the critical interfaces between value-decisions and actions. In the final two studies, we examine decisions that require integrating reward and physical effort, an action-related cost. We propose a behavioural model for the impact of effort costs on reward valuation and use fMRI to show that the comparison of rewards tied to efforts is mediated by a region in anterior cingulate cortex. Collectively, these studies reveal some of the neuro-anatomical substrates and inter-regional interactions that enable the brain to translate value-decisions into actions.

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