An important function of attention is the selection of information from our complex sensory environment. It is generally assumed that a collection of hierarchical filters provides various levels of selection. One of these levels is considered to select information among sensory modalities, which leads to amplified processing of stimuli in the attended modality compared to stimuli in the unattended modality (intermodal attention). In this thesis five electroencephalographic (EEG) experiments were conducted, investigating the influence of intermodal attention on steady-state responses (SSRs). Steady-state responses are continuous oscillatory brain responses elicited by periodic stimulation, such as flickering visual stimuli (vSSR) or amplitude modulations in a sound (aSSR).
In the first two experiments, attention effects for the aSSR were compared to modulations in the event related potential (ERP) during transient stimulation. Differences in the time course and topographies of attention effects in both brain responses suggest that they might indicate different aspects or processing levels of intermodal attention.
The steady-state response has the same fundamental frequency as the periodic rhythm of the stimulation, and thus allows the investigation of the neural dynamics involved in sustained attention to multiple stimuli. Thus, sustained intermodal attention was investigated for the aSSR and vSSR simultaneously in the following three experiments during detection and discrimination tasks. Although aSSR and vSSR were mainly modulated in modality-specific areas, source analyses point towards the additional involvement of a supramodal attention network in intermodal attention, with attentional modulations found in multisensory areas but also in non-preferred modality-specific areas. The illustrated modulation of the SSRs during intermodal stimulation shown in these experiments could open a whole new and exciting avenue of research to uncover basic neural mechanisms of intermodal attention in the human brain.
An important function of attention is the selection of information from our complex sensory environment. It is generally assumed that a collection of hierarchical filters provides various levels of