NCCI 2010 -National Conference on Computational Instrumentation CSIO Chandigarh, INDIA, 19-20 March 2010 51 EEG PURGING USING LABVIEW BASED WAVELET ANALYSIS Jigar D. Shah, M. S. Panse Veermata Jijabai Technological Institute (VJTI) Mumbai welcomebyjigarshah@gmail.com Abstract: The Electroencephalogram (EEG) is a biological signal that represents the electrical activity of the brain. Artifacts in EEG signals are caused by various factors, like line interference, EOG (electro-oculogram) and ECG (electrocardiogram). The removal of artifact from scalp EEGs is of considerable importance for analysis of underlying brainwave activity. The presence of artifacts such as muscle activity, eye blinks, pulse signals and line noise in electroencephalographic (EEG) recordings obscures the underlying processes. These artifacts sources increase the difficulty in analyzing the EEG. For this reason, it is necessary to design a procedure to decrease such artifacts in EEG. A commonly encountered problem in artifact removal is the ‘blanking’ of the EEG signal due to blinking of the patient’s eyes. In biomedical analysis, EEG signal consists of artifacts. The fundamental basis of the paper here is to address the elimination of ocular artifact called Electroculogram (EOG) from Electroencephalogram (EEG) signal using wavelet method on Laboratory Virtual Instrumentation Engineering Workbench (LabVIEW) platform. An algorithm using wavelet analysis is implemented to eliminate the eye blink artifact without compromising the integrity of the primary EEG data. Keywords – Ocular artifact, haar wavelet, EEG, Discreet Wavelet Transform, EOG. 1. INTRODUCTION Normal EEG signals are usually registered from electrodes placed on the scalp and are often very small in amplitude of order 20 μV. The electroencephalogram (EEG) contains useful diagnostic information on a variety of neurological disorders. It is a non- invasive method used to measure the electrical activity of human brain. The EEG like all biomedical signals is very susceptible to a variety of large signal contamination or artifacts (signals of other than brain activity) which reduce its usefulness [1]. Blinking or moving eyes produces large electrical potentials around the eyes called the electro-oculogram (EOG). The EOG spreads across the scalp to contaminate the EEG, when it is referred to as an ocular artifact (OA). For example, In Figure 1, the effects of blinks and eye movements on an EEG and an EOG are illustrated. The upper two plots illustrate EEG and EOG during which no significant eye movements or blinks occur. The middle two plots show the effect of two brief eye movements. The change in amplitude that is caused by the movement is more prominent in the right plot because the EOG is recorded closer to the eyes. The lower two plots illustrate the effect of a blink. Figure 1 Illustration of the effects of eye movements and blinks in the EEG and in the EOG. LabVIEW is graphical programming environment. Programs in IDE are called Virtual Instruments (VIs), consists of a Block Diagram (BD) and a Front Panel (FP). A BD provides a graphical code development environment whereas a FP allows the user to interact with a VI. It provides an efficient and easy-to-use environment for code development especially when the user needs to interact with the program and visualize the results. Unlike text-based programming languages like C which follow a control flow execution model, the environment of programming follows a dataflow execution model. 2. OCULAR ARTIFACT REMOVAL METHODS To eliminate artifacts is prevent them from occurring in the first place. Of course prohibiting