Mechanisms and effects of interference at different stages of information processing

Everyday situations illustrate, how interference at the different levels of information processing affects our behaviour. For example while driving a car an attractive bill-board, a change of traffic lights or playing children at the roadside can distract the driver or interfere with prepotent responses. The main focus of our research is to understand how the brain detects and resolves conflict between different representations (for instance between perceptual information, memory contents or prepotent motor responses). There is an ongoing discussion, if detection and control of conflicting representations could be dedicated to a common system. Alternatively different subsystems may be responsible at different levels of information processing. Furthermore, the functional role of identified brain areas is often discussed controversial. The methods we use to further clarify these questions are psychophysics, functional magnetic resonance imaging (fMRI), recording of event-related potentials (ERP) from scalp electrodes, transcranial magnetic stimulation (TMS) and patient studies. The combination of the high spatial resolution of fMRI (~ 1 mm³) with the high time resolution of ERP (ms) allows a more detailed analysis of the function and the exact time course of activated brain areas. Our studies are mainly performed in healthy subjects, but to verify the attribution of a certain function to a specific brain area, it should also be demonstrated that a lesion of this area alters the function. For this reason, we use repetitive TMS in healthy subjects to induce a so-called "virtual lesion". Because of its low depth of penetration, only superficial (cortical) brain areas could be interfered with. Therefore, additional studies in selected patients with isolated focal brain lesions are being performed.

Adaptive attention mechanisms in conflict processing

Adaptive changes of the visual spatial attention, which are induced by a conflict, will be examined in healthy subjects. The well-established location negative priming paradigm is suitable for this and has been adapted in our previous work. We will now examine these experimental paradigms with electrophysiological methods (ERP) and with functional MRI (fMRI) in order to systematically locate individual subfunctions of the conflict processing. In particular we are interested in the adaptive attention processes to anatomically defined parts of a neural network. Behaviour parameters will be manipulated by systematic variation of the selection difficulty and the conflict strength respectively in such a way that they can be correlated with changes of the activity samples. In the context of justified neuroanatomical hypotheses dynamic changes in the interaction of individual network junctions will be quantified by connectivity analysis and set systematically with experimental variables (e.g. behavior data, ERP) in relation. Thus we strive for a more precise function specific allocation of adaptive attention changes during a conflict to individual components of the fronto-parietal network and early visual areas.

This project is funded by the DFG Forschergruppe FOR 778/1.