Research fields
Research
Our overarching research aim is to better understand the neural mechanisms underlying (the learning of) flexible goal-directed behavior. To achieve this, we employ different research methods, including behavioral assessment, functional magnetic resonance imaging (fMRI), transcranial magnetic stimulation (TMS), electroencephalography (EEG), as well as combinations such as TMS-fMRI and EEG-fMRI. We apply advanced analysis methods to characterize (learning-related) changes in functional connectivity and in distributed neural representations.
Current topics
Instruction-based Learning
Volitional control of action enables the flexible selection of the one behavior that appears most appropriate in the current situation. To achieve this, an organisms faces several challenges, depending on its learning history. For instance, if the goal is set (e.g. to have a coffee), but the means to achieve this goal in the current situation are unknown, it is crucial to figure out what the ‘correct’ action is. One way to achieve this is to engage in trial-and-error learning which relies on evaluating retrospectively whether an action performed under certain stimulus conditions yielded a desired outcome. Another learning strategy exploits the highly developed human communication skills and relies on explicit instructions as an acquisition shortcut (e.g., by consulting the operating instructions of the coffee maker or by observing someone else demonstrating the operation of the machine). In contrast to trial-and-error learning, instructions specify prospectively how to yield intended outcomes under the appropriate stimulus conditions, thereby avoiding errors and potentially harmful consequences.
Competition between habitual and goal-directed action Control
A crucial aspect of volitional control pertains to the fact, that in virtually any situation we can choose among a variety of different actions, each of which has successfully served to yield different goals in the past (just imagine the numerous goals you could pursue by different uses of a kitchen knife). There is rarely one single correct action in a given situation and the goal to simply ‘take the correct action’ is obviously underspecified unless a specific goal is determined. Thus, in this case, volitional control means selecting the action that has previously served to achieve specifically the currently pursued goal. Importantly, action selection is typically not only challenged due to competing goals or competing action-goal associations, but also due to directly stimulus-induced action tendencies that may override any goal-directed choices. It is therefore crucial to examine goal-directed action control in direct contrast to stimulus-bound control and to consider possible variables that may shift the balance between these competing influences on choice behavior (such as acute stress).
Past (but not forgotten) topics
Strategies in Rule-based behavior
The impressive number of recreational games that have been invented throughout the centuries demonstrates that humans enjoy learning, applying, and flexibly combining even the most arbitrary rules, but we most certainly adopt different strategies in doing so. Recent studies revealed striking interindividual differences, both behaviourally and in terms of brain activation for even simple and well-controlled experimental paradigms. It is crucial to consider these differences to foster our understanding of both the processes under investigation and the functionality of cortical areas taken to subserve them. This project examines the neurocognitive basis of strategy-application in rule learning, application, and integration combining behavioural and neuroimaging methods.
Preparatory control in task switching
Human behavior is flexible in that it is organized according to the anticipated future consequences of action (i.e., goals) rather than merely reacting upon current sensory inputs (see project ‘action control’). Another variety of behavioral flexibility is that goals can be adjusted and switched momentarily. This ability has been extensively examined within the task switching paradigm. Using fMRI and EEG methodologies, we have been interested in characterizing the multi-facetted nature of preparatory processes in anticipation of implementing a changed task goal.
FMRI-based mental chronometry
Mental processes naturally evolve across time both serially and in parallel. An important endeavor tightly linked to the classical notion of mental chronometry therefore is to determine the flow of information processing that transforms sensory inputs into high-order mental representations and overt behavior. Due to the slow evolution of event-related hemodynamic responses fMRI-based mental chronometry has been notoriously difficult. This project attempts to recover temporal process information by extracting BOLD response timing parameters associated with the experimentally controlled temporal structure of successive events. Currently, this approach is used to evaluate the impact of random vs. blocked foreperiods in forced-choice and task switching paradigms. Furthermore we explore the challenges and potential benefits of sub-second whole brain acquisition of functional MRI data for fMRI-based mental chronometry.