Surface Laplacian based Single Channel Activity (SCA) in control subjects and stroke patients

Abstract

Event Abstract Back to Event Surface Laplacian based Single Channel Activity (SCA) in control subjects and stroke patients K. Fulop1*, Vegso B1, Cs Szekrenyesi1, T. Magos1, M. Dombovari1, Gy Kozmann1 and Z. Nagy1 1 Universtity of Pannonia, Department of Electrical Engineering and Information Systems, Faculty of Information Technology, Hungary Aim: Sequential activity of cortical areas is responsible for preparation and execution of motor activity. High power 128 channels EEG with its 0.5 msec temporal resolution promises an appropriate technique to study brain function in a "mesoscopic" level. Methods: Visually guided left- and right-hand finger tapping experiments are carried out in an electrically shielded room on right handed subjects using a 128+9 channels EEG device at 2048Hz sampling rate. The tapping is performed at a predefined pace with 10 seconds inter-tap interval, 32 tapping epochs are selected for processing. Power line noise removal is followed by band-passing the signal to 1-400Hz, leaving the selected 3072 sample (1500ms) data epoch clean. A 500ms pre-tapping interval is selected as baseline phase, 500-500ms before and after tapping intervals are considered for further processing. The 128 scalp electrodes are grouped by anatomical relevance to the task. Two dimensional discrete Surface Laplacian calculations allow for estimation of radial cortical surface current density (SCD), which is averaged over the 32 selected tapping epochs. Threshold values are calculated from the baseline interval to determine radial current density limits of activation (Single Channel Activity - SCA). The activation level of the anatomically defined regions were characterised by the accumulated SCD values. Results: Age related increase of activated SCA was documented in control subjects. In young age group the relevant motor and premotor activity was moderate compared to the elderly control subjects. Immediately following stroke the relevant activity was poorly detectable while in the course of rehabilitation the typical motor and premotor activity has returned. Conclusion: We developed a new Surface Laplacian based technology (SCA) [1] capable of characterizing task related activation of motor and premotor cortex and following the post-stroke repair phenomenon. The technique also proved to be a useful tool for assessing lateralization. Acknowledgments: Granted by NeuroMath Action BM0601, OTKA K69240, NTP OM00191/2008 AALAMSRK.