In this EEG study, we aim to answer the question how the detection or discrimination of visual stimuli differs in terms of the involvement of the functional communication between different neural modules as proposed by the Dynamic Attentional Workspace Account (DAWA). The following modules are proposed to be involved: visuospatial sensory representations (VIS), a supramodal spatial attention module (SAM) which directs and facilitates the coupling of selected sensory information with relevant action programs, and an action module (ACT) in which the motor programs are being acticated and executed.
We are focusing here on the mechanisms of visuospatial stimulus selection. Thus, we utilized the classical method of spatial cueing: participants’ attention was directed by symbolic cues (arrows) indicating the most probable target location. Either a simple target detection and simple response, or a target discrimination and two-choice response were required - as the DAWA predicts different dynamics of attentional processes depending on response requirements. In the detection task, the required action program is already prepared in advance, whereas in the discrimination task, the action selection is possible only after selecting and discriminating the target stimuli.
We are carrying out event-related potential (ERP) and time-frequency analyses, to identify electrophysiological markers of attention-related processes. Specifically, we analyze the hemispheric lateralizations of spatial selection-related ERPs and oscillatory alpha- and theta-band power and phase coherence, as well as functional connectivity between the areas assumed to be related to the postulated neural modules. Thus, we expect that the results will unravel action-specific functional integration between the VIS, SAM, and ACT modules.
Fig. 1 The task, stimuli, trial timeline, and response requirements used in the present experiment. Each trial began with a fixation point. Next, a cue (in this example a right-pointing green arrow) was presented at the center of computer screen, to indicate the most probable target location; 1 sec after cue onset, a target (horizontally or vertically oriented Gabor patch) was presented either in the left or right visual field. In the detection task, participants were required to respond with only one button (using either left or right hand, which changed block-wise) regardless of the target location and orientation of the Gabor lines. In the discrimination task, participants were required to respond for horizontal Gabor lines by pressing one button, and for vertical Gabor lines by pressing the other button, regardless the target location.