Search

Abstract: We used high-density event-related potentials (ERP) in a modified flanker paradigm to study the role of anticipated action consequences in action planning and the role of anticipation in the perception of action consequences. Prior to the experiment, participants were trained to classify target letters in a four-alternative forced-choice task; another letter was presented as an effect following each response. After participants had thus acquired the response–effect contingencies, in the experiment effect letters were presented as flankers to target letters. Effect-compatible flankers were letters that were learned as effects of the correct response to the target; effect-incompatible ones were learned as effects of other responses; neutral flankers were never presented as action effects. To help distinguish early and late effects of flankers on target processing, flankers were presented either simultaneously with the target or after a delay. We found that effect-incompatible flankers resulted in longer, than other flankers, time between the onset of the response-locked lateralized readiness potential and the response, indicating extended motor processing. ERP evoked by the effect-incompatible flankers differed from those evoked by other flankers in early perceptual component P1 and in later frontal component P2 reflecting stimulus evaluation and conflict detection. These results show that anticipating action consequences involves brain systems ranging from perceptual to executive; anticipated action effects constitute a link between perception and action. [Copyright &y& Elsevier]

Abstract: Objective: Data from a previous event-related potential (ERP) study in visual-perceptual grouping [Nikolaev AR, van Leeuwen C. Flexibility in spatial and non-spatial feature grouping: an event-related potentials study. Brain Res Cogn Brain Res 2004;22:13–25] were re-analyzed to identify event-related dynamics of phase-synchronization. Methods: In 20Hz activity, uniform spreading of phase synchronization in closely spaced (∼2cm) scalp electrodes appears and disappears spontaneously. The lengths of synchronized activity intervals and how they vary as a function of stimulus presentation were compared between task and control conditions. Results: Synchronization reached a maximum in the task condition about 180ms post-stimulus onset, coinciding with the peak N180 ERP marking the deployment of task-specific attention. Synchronized intervals were longer in the task than in the control condition. Long (above 80ms) intervals occurred at a stable rate before and just after stimulus onset, but steeply decreased 200–400ms afterwards. Conclusions: Perceptual tasks lead to longer synchronized intervals in early visual areas. Attention deployment resets the ongoing synchronization. Event-related activity, besides low-frequency ERP, consists of high-frequency short and long synchronized intervals corresponding to evoked bursts and ongoing oscillations, respectively. Significance: High-density scalp recorded EEG revealed synchronization dynamics in a local, early visual area of cortex that can be interpreted as modulation of spontaneous ongoing task-related processes by attention. [Copyright &y& Elsevier]

Abstract: In a visual task using 12 healthy subjects, spread of evoked phase-synchronized activity was studied in local cortical areas. The areas were identified in a previous study of the same data set using event-related potentials (ERP). Chains of closely spaced (∼2 cm) scalp electrodes covering these areas were selected for phase synchronization analysis in which task and control conditions were compared. Phase synchronization spreading in the task condition at 20 Hz reached a maximum about 180 ms post-stimulus in the right occipital area. This maximum coincides with the attention-related negative peak N180 in the corresponding ERP study. Intervals of evoked phase synchronization were longer in the task than in control condition. It was concluded that attention-related modulation of evoked activity is reflected not only in enhanced amplitude of low-frequency ERP, but also in phase synchronization of high-frequency ongoing rhythms in local brain areas. [Copyright &y& Elsevier]

High-density, 256-channel, event-related potentials (ERP) were recorded in 12 subjects, who had to find a triangle of which only the corners were marked in an array of distracters. The orientation of the corner markers to each other and their proximity varied across trials. An early, pre-attentional, nonspatial effect of marker orientation was found at 64 and 100 ms after stimulus presentation in the right occipital areas. A spatial effect of marker proximity (triangle size) was reflected in a negative peak of 180 ms in the occipital areas and in P250 and P430 in the central areas. This result is contrary to the usual precedence of spatial over nonspatial grouping and suggests a greater flexibility in precedence based on task demands. [Copyright &y& Elsevier]