Quantification and visualization of eventrelated changes in oscillatory brain activity in the timefrequency domain

Bernhard Graimann* and Gert Pfurtscheller Laboratory of Brain- Computer Interfaces (BCI-Lab), Institute for Knowledge Discovery, Graz University of Abstract In this chapter we review the traditional approach for ERD ERS quantification and a more recent approach based on wavelet transform. In particular, we address the visualization of these phenomena and the validation of the results through statistical significance testing. Furthermore, we report on preprocessing using independent component...

Conclusion

Cortical (de)activation can be assessed by different methods such as ERD ERS quantification in the EEG, TMS, and fMRI. Activated cortical areas involved in a motor task are characterized by decreased alpha (mu) oscillations (ERD) (Pfurtschel-ler and Lopes da Silva, 1999a) and increased responses to TMS and a positive BOLD signal (Logothetis et al., 2001 Hummel et al., 2002, 2004 Rau et al., 2003), and corresponds to a right-side shift in the CAM. Deactivation (removal of excitation back to...

Meg

EEG electrode and MEG sensor positions used in the study 127 EEG electrodes and 148 MEG sensors (magnetometers). The EEG electrodes are located on the scalp, whereas the MEG sensors are located around 2 cm from the scalp in a helmet (not shown). The EEG electrodes were organized into regional groups on the basisof the nearest 10 20 electrode position. The MEG sensors were similarly grouped by first projecting sensor positions onto the head. The labels in each figure indicate the groups...

ERDERS depends on the level of consciousness

Oscillations in the alpha band can display either ERD or ERS depending on the level of consciousness. This was supported by a follow-up study in a comatose patient with a brainstem hemorrhage, where visual stimuli were applied in deep coma (starting with Glasgow Coma Scale, GCS 4) and after recovery from coma (GCS 15). In the first case, visual stimuli induced bursts of oscillations (ERS), while in the second case, the same physical stimulus resulted in an ERD (Pfurtscheller, 1992). Induced...

Info

Increased EEG gamma coherence has also been observed in perceptual and working memory tasks and in the process of associative learning (Miltner et al., 1999 Tallon-Baudry, 2003). While numerous reports have focused on the gamma coherence changes, studies examining short-term memory processes and target detection tasks where an internal representation of the target is established have revealed increased coherence at lower EEG frequencies including the beta, alpha, theta, and delta ranges....

Experimental strategy and procedure for differentiation of facial expressions angry and happy

Angry Facial Expressions Pics

As stimulation, we have used the photographs of eight persons, students of Department of Performing Arts, who have been asked to mimic angry and happy expressions. At the first group, we had 16 photographs that include eight of each person's facial expressions mimicking two different facial expressions. As stimulation, we have selected randomly 6 out of 16 photographs of 3 different persons in 2 measuring sequences. The pictures were presented to the subjects under similar conditions of the...

References

Brechet, R. and Lecasable, R. (1965) Reactivity of mu-rhythm to flicker. Electroencephalogr. Clin. Neurophysiol., 18 721-722. Cassim, F., Monaca, C., Szurhai, W., Buorriez, J.L., Defebvre, L., Derambure, P. and Guieu, J.D. (2001) Does post-movement beta synchronization reflect an idling motor cortex Neuroreport, 12(17) 3859-3863. Chen, R., Corwell, B. and Hallett, M. (1999) Modulation of motor cortex excitability by median nerve and digit stimulation. Exp. Brain Res., 129 77-86. Chen, R.,...

List of Contributors

Ba ar, Faculty of Science and Letters, Istanbul Kultur University, Istanbul, Turkey M. Bastiaansen, FC Donders Centre for Cognitive Neuroimaging, Radboud University, Trigon Building, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands N. Birbaumer, National Institutes of Health (NIH), NINDS Human Cortical Physiology, Building 10, 5th floor, Bethesda, MD 20892, USA and Institute of Medical Psychology and Behavioral Neurobiology, University of Tuebingen, D-72074 Tuebingen, Germany M. Bockova,...

Simultaneous occurrence of ERD and ERS at one cortical location

A cortical area is composed of different networks and can therefore generate a variety of oscillations in the alpha, beta, and gamma bands. For example, an interaction between alpha and gamma band oscillations in sensorimotor areas exists in such a way that gamma bursts are very often embedded in desynchronized or blocked alpha waves. Such a simultaneous occurrence of both alpha ERD and gamma ERS in single recordings of EEG and electrocorticography (ECoG) in a movement task has been reported by...

Source analysis by highresolution EEG methods

High-resolution EEG methods are based on a conceptual framework that differs substantially from that of source localization. The current source distribution in the cranial volume cannot be estimated uniquely using only data recorded on the scalp surface. Assumptions must be applied by all source localization methods to arrive at source location estimates. By contrast, high-resolution EEG methods do not require any assumptions about the sources instead they enhance the sensitivity of each...

The concept of phase resetting

Event-related activities (ERD ERS) cannot be extracted simply by averaging the EEG signals but have to be detected by frequency analysis as indicated above. In contrast, the common evoked potentials (EPs) are usually detected by averaging, since the generally accepted idea is that a sensory evoked response can be accounted for by a simple summation model, where the evoked activity is assumed to be linearly added to the on-going, or background, EEG or MEG activity. The interaction between the...

P2

Where w is the weighting vector (the first row in the spatial filter matrix), and pk, k e 1,2 denotes the baseline or reference period and the activity period, respectively. The general solution for this problem is the principal component of the jointly pre-whitened samples of the two periods under consideration (Fukunaga, 1990), which is also known as the method of CSPs (Koles et al., 1995 Muller-Gerking et al., 1999). A derivation of the solution in the context of ERD ERS analysis is given in...

Time

Structure of sequential mental rotation task. Note all objects were rotated about the vertical axis. Fig. 2. Cross subject average of steady-state visually evoked potential event-related partial coherence (SSVEP-ERPC) between electrode 21 (left-frontal midway between F7 and T3) and P4 (right parietal) for all correct responses to matching trials. Labels indicate the angular disparity between first and second objects. Mean reaction time increased linearly from the 60 condition (RT 2.19...

Dynamic sculpting of brain functional connectivity and mental rotation aptitude

Brain Sciences Institute, Swinburne University of Technology, John Street, Hawthorne, Melbourne, Abstract Changes in long-range synchronization are considered a key mechanism for the integration and segregation of cortical regions mediating cognitive processes. Such synchronization or functional connectivity is reflected in human electroencephalograph EEG coherence and in steady-state visually evoked potential SSVEP coherence. In this chapter, the relationship between cognitive proficiency in...