which requires pseudowords recall. In case of the VSP, we also used adual-task: Go–NoGo task and another which requires visual matrixrecalling.

Results: For tasks that mainly measure the CE capacity, a greaterP300 amplitude in frontocentral regions was observed. This effectwas only significant for the high attentional requirement task. For thetask that assessed load effects on PL, a significant decrease in P300amplitude was observed in response to an upload. However, for thetask that assessed load effects on VSP, there were no changes in P300amplitude or latency.

It is concluded that high attentional requirement and high load ofverbal stimuli seem to modulate P300 amplitude in these dual tasks.Loading the specific WM components affected the EC in differentways: Loading the PL showed negative effects on the EC (i.e.decreasing EC capacity), however loading the VSP seem to have noeffects on CE.

Supported: CONACYT 59066.

doi:10.1016/j.ijpsycho.2010.06.202

The critical nature of between- and within-subjects variation inevent-related brain oscillatory EEG responses

Christina M. Krausea, Aleksander Alafuzoffa, Mari Lainea,Ricardo Vigárioba Cognitive Science Unit, Institute of Behavioral Sciences,University of Helsinki, Finlandb Department of Information and Computer Science, Aalto University,Finland

It has been suggested that brain electric oscillatory networksprovide a potential mechanism for large-scale and long-distanceneural communication and interaction, enabling temporally preciseand spatially distributed information processing. Recent reports onthe relationships between brain oscillatory EEG responses and humancognitive capacities (i.e., information processing) are indeed promis-ing: event-related brain oscillatory responses of different frequencieshave successfully been correlated with specific cognitive processes.However, many of these studies have been performed on relativelysmall samples and the results have typically been reported as averageresponses over several stimulus presentations and additionally asaverage responses over the sample. The current presentation willreport novel observations on the magnitude of between- and within-subjects (trial-to-trial) variation in brain oscillatory 1–40 Hz EEGresponses during auditory memory processes, encoding and recogni-tion. The effects of memory load on the brain oscillatory responsesare discussed, too.

Brain oscillatory EEG responses were analyzed from 17 normalsubjects while they performed an auditory memory task with threememory load conditions (memory sets: 5, 7 or 9 words to beencoded, the probe always being one word).

Both the between- and within-subjects variation in the brainoscillatory responses was of notable magnitude. The between-subjects variation was of greater magnitude than the within-subjectsvariation.

This presentation discusses the possible causes for and con-sequences of this variation in brain oscillatory responses duringcognitive processing. The awareness of this variation raises someconcerns about the conclusions and generalizations made fromstudies in cognitive neuroscience.

doi:10.1016/j.ijpsycho.2010.06.203

Hierarchical control structures of the frontal theta and alphaactivity for the dual auditory and visual working memory task

Masahiro Kawasakia, Keiichi Kitajoa,b,c, Yoko Yamaguchia,ba Rhythm-based Brain Computation Unit, RIKEN BSI-TOYOTACollaboration Center, Japanb Laboratory for Dynamics of Emergent Intelligence,RIKEN Brain Science Institute, Japanc PRESTO, Japan Science and Technology Agency (JST), Japan

Human flexible multi-information processing is executed byworking memory (WM) which includes not only temporallyspecialized storage, such as a visuospatial sketchpad and phonologi-cal loop, but also executive function which manipulates mentallystored representations. Our recent EEG studies have proposed thatthe dynamic linking between theta oscillations and modality-specificalpha oscillations mediates communication between the centralexecutive functions and storage buffer functions in WM (Kawasaki,et al., 2010). However, little is known about how these oscillationscontribute to the dual tasks.

In this study, we used time-frequency analyses of 62-channel-EEGdata for 2 types of WM manipulation tasks: an auditory WM task,which required mental calculation of numbers presented through anauditory stimulus; and a visual WM task, which required theparticipants to move a spatial location in a mental representation inaccordance with a visual stimulus. Fourteen participants (meanage=27.9 years) engaged in 4 conditions: single auditory WM(Fig. 1A), single visual WM (Fig. 1B), simultaneous dual WM(Fig. 1C), and sequential dual WM (Fig. 1D) conditions. The behavioralaccuracy rates showed no significant differences among conditions(auditory, 95.2%; visual, 97.1%; simultaneous, 91.1%; sequential, 94.9%).

Under the single WM conditions, the frontal theta (6 Hz) andalpha (10–12 Hz) amplitudes increased during the manipulationperiods, whereas the alpha amplitudes increased during the main-tenance periods in the temporal area for the auditory WM and theparietal area for the visual WM. On the other hand, in themanipulation periods of the dual WM, especially in the simultaneouscondition, the enhanced frontal theta amplitudes persisted after thealpha amplitudes were diminished. The frontal activities for dual WMtasks were significantly higher than those for single WM tasks. Theseresults suggested that the concurrent frontal theta and alpha activitywould be associated with the hierarchical control structures of themultiple operations in dual WM tasks.

doi:10.1016/j.ijpsycho.2010.06.204

305Abstracts / International Journal of Psychophysiology 77 (2010) 288–342