Lieven Lagae

Reduction of alpha distortion in event related potentials

A frequently used brain monitoring technique in cognitive neuroscience research are Event Related Potentials (ERPs). ERPs are electrical brain responses to specific sensory, cognitive and motor events in electroencephalographic (EEG) data. However, ERPs are known to have a very low signal-to- noise-ratio and suffer from artifacts present in EEG data like ocular and muscular artifacts. Another common type of distortion is alpha activity. The aim of this study is to remove this activity with different mathematical approaches. Classical methods like filtering and independent component analysis (ICA) do not yield good results in the reduction of alpha distortion. Therefore, we propose Parallel Factor Analysis or PARAFAC as a method for reducing the alpha activity. We will show why filtering and ICA fail to solve this problem and how PARAFAC does succeed in improving the quality of the measured ERPs.

P01.4 Cardiac autonomic dysfunction in West syndrome

Background: West syndrome is an age-dependent epileptic encephalopathy. Autonomic changes are increasingly being recognized in patients with epilepsy: cardiac autonomic function is mediated by sympathetic and parasympathetic efferent activity to the heart and can provide information on the functional state of the autonomic nervous system. Methods: Cardiac autonomic function was evaluated in 13 patients with West syndrome by measuring heart rate variability during 5minute epochs of ECG in wake, stage 2 and slow wave sleep. In 5 patients who developed subsequently another type of epilepsy, a second evaluation was performed after 3 years of follow-up. Results: Results showed a lower heart rate in stage 2 sleep in patients with West syndrome. Spectral components did not show significant differences compared to age matched controls at the moment of presentation. After follow-up of 3 years we were able to demonstrate higher low frequency (LF), lower high frequency (HF) and a higher LF/HF ratio during slow wave sleep. Conclusion: This study shows a lower heart rate in patients presenting with West syndrome, already at the onset of the syndrome, even before treatment. After follow-up of only 3 years of epilepsy, chronic autonomic changes appear in the spectral components of heart rate variability.